This is a pair of modules that Maplin was selling some time back, to send stereo audio over a 2.4GHz radio link. The transmitter identifies as a USB sound card, I’ve personally used these units to transmit audio about 60ft. The transmitter, above, has a single button for pairing with the receiver below.
Receiver
The receiver unit has a large external antenna, a link status LED & volume buttons, these directly control the volume level on the host PC via the sound card drivers.
Receiver PCB Top
Popping the case open on the receiver reveals a large PCB, holding the chipset, along with the audio output jacks & Mini-USB power input. The antenna Coax is soldered to the PCB.
Receiver PCB Bottom
The top of the board has the control buttons, and the status LED.
Receiver Chipset
The chipset used here is a Nordic Semiconductor nRF20Z01 2.4GHz Stereo Audio Streamer, there’s a small microcontroller which does all the register magic on the RF transceiver. The RF chain is at the top of the photo, audio outputs on the top left, and the micro USB power input & voltage regulators at bottom left.
Transmitter PCB Top
The transmitter PCB has a Sonix USB Audio Codec, to interface with the host PC. This is then fed into another Nordic Semi part on the opposite side of the board:
Transmitter PCB Bottom
The bottom of the transmitter has the RF section, and another small control microcontroller.
In an effort to reduce the level of superflous stock I have in the workshop, I’ve set up a new store to sell off some of these parts & modules. It can be found over at store.experimental-engineering.co.uk. I’m still building the inventory, and new items are being added all the time. The money raised will go towards new posts & projects.
As many will already know, we lost a guiding light in the Rock World last week, Chester Bennington of Linkin Park. I am reposting the message from the other bandmembers here, being one of the first bands I ever listened to of this genre. As someone with mental illness, seeing someone identify their depression, and having it still kill them is rather disturbing.
RIP Chester, Forever With Us In Song
Dear Chester,
Our hearts are broken. The shockwaves of grief and denial are still sweeping through our family as we come to grips with what has happened.
You touched so many lives, maybe even more than you realized. In the past few days, we’ve seen an outpouring of love and support, both public and private, from around the world. Talinda and the family appreciate it, and want the world to know that you were the best husband, son, and father; the family will never be whole without you.
Talking with you about the years ahead together, your excitement was infectious. Your absence leaves a void that can never be filled—a boisterous, funny, ambitious, creative, kind, generous voice in the room is missing. We’re trying to remind ourselves that the demons who took you away from us were always part of the deal. After all, it was the way you sang about those demons that made everyone fall in love with you in the first place. You fearlessly put them on display, and in doing so, brought us together and taught us to be more human. You had the biggest heart, and managed to wear it on your sleeve.
Our love for making and performing music is inextinguishable. While we don’t know what path our future may take, we know that each of our lives was made better by you. Thank you for that gift. We love you, and miss you so much.
As quickly as it came round again, the festival is over. The yearly photos are over here, along with some extra content in the form of Demolition Download videos – brought to us by Battle Heritage UK! Enjoy.
Here’s something different – below is a standard domestic carbon monoxide alarm, (I did a teardown of the same detector here), but in this case it’s not detecting any carbon monoxide, but another gas in the surrounding atmosphere. We recently had an issue with these detectors on board the boat, the alarms were sounding in the middle of the night, at ridiculous levels displayed, with no fuel-burning appliances running! While it didn’t become obvious at the time, the gas being detected was hydrogen, given off from the house battery bank while they were on charge.
CO Detector
I have long been aware of the fact that electrochemical gas sensors have some cross-sensitivity, and sensors are available that are specifically designed to not respond to other gases (hydrogen in particular, as this gas is actually part of the sensor reaction. Much more information about the subject is over here). I’ve no doubt these more industrial grade sensors are much more expensive than the cheap kind used in domestic alarms though, not to mention there aren’t usually massive lead-acid battery banks in houses, so the concept of having hydrogen in the air doesn’t usually happen.
However, I’ve seen plenty of these exact type, and other types of the same brand used on boats. The user manual for this particular alarm doesn’t mention the possibility of cross-sensitivity though, and this could lead someone to doubt their alarm is working correctly, and to stop trusting it or remove it entirely due to false triggering.
As I’ve not been able to find any data on the sensor used in this detector, I don’t know how sensitive it is to hydrogen, the image above was taken with an alarm placed directly over the cell opening of a large lead-acid battery on charge at 14.7v to deliberately cause some gassing. This was the highest reading obtained, the detector didn’t take long to respond either. As the gas mix coming out of the cell is 2:1 H²/O² this reading is clearly low, but it’s still plenty enough to sound the alarm within a few minutes.
For us on boats, with potentially explosive gas mixtures being able to gather this cross sensitivity is potentially a good thing – the alarm made sure we were well aware of something going wrong before a dangerous concentration was present. (Hydrogen is flammable in air between 4% & 75%).
To prevent this happening in future, I’ll be installing some forced ventilation into the battery compartment, triggered by a hydrogen sensor. More to come on this soon!
It has come to my attention via Google’s Webmaster Tools, that they’re reporting that malware has been found on my blog here, and are apparently going to issue site malware warnings to people about this when they click on links to this site. However it seems even Google can’t tell me where they’ve apparently found this through crawling the site:
Malware
Here is the listing from GWT, but it’s totally blank! The download all samples link also gives a totally blank CSV file. This matches my own searching through the file structure of the blog with a malware scanner, (and ClamAV to check my binary downloads), as I’ve not found anything either.
Google didn’t think it prudent to email me about this either, I only discovered these warnings this evening on checking my account; yet I get an email within 4 hours of deleting something, from the bot complaining that a page suddenly isn’t available any longer. This simply isn’t the way to do things Google, and as far as I can see these warnings have been in error, as I’ve not managed to generate an error by clicking on one of my site links in Google’s listings (from a different location, and browser, with no connection to any of my accounts, to make sure I’m not skewing the result).
Even stranger, is that my old domain name, insideelectronics.co.uk (which is still live, and redirected with a 301 to the new domain of experimental-engineering.co.uk), isn’t showing any of these site malware warnings in GWT, adding further to my suspicion that this is just Google spouting total bollocks.
However if any readers have encountered one of these apparent site malware warnings, please let me know so I can get this fixed as soon as possible. I’ve requested a review with Google to clarify things, but I don’t expect to hear back from them for at least 72 hours. Traffic doesn’t seem to have been affected so far, which probably means that none have been displayed to readers but I don’t know how long these site malware warnings have been in place.
Over the past few weeks, the host I’ve been with for over 3 years, OVH, announced a rather large price increase of 20% because of Brexit – the current universal excuse to squeeze the customer for more cash. This change has sent the price of my dedicated server solution with them to over £45 a month. Doing some napkin-calculation gave me £18 a month in extra power to run a small server locally. So I’ve decided to bring the hosting solution back to my local network & run from my domestic internet link, which at 200Mbit/s DL & 20Mbit/s UL should be plenty fast enough to handle the modest levels of traffic I usually get.
Obviously, some hardware was required for this, so I obtained this beauty cheap on eBay:
HP Proliant MicroServer Gen 8
This is a Gen 8 HP Proliant Microserver, very small & quiet, perfect for the job. This came with 4GB of RAM installed from the factory, and a Celeron G1610T running at 2.3GHz. Both are a little limited, so some upgrades will be made to the system.
Disk Bays
4 SATA drive bays are located behind the magnetically-locked front door, there’s a 250GB boot disk in here along with a pair of 500GB disks in RAID1 to handle the website files & databases. For my online file hosting site, the server has a backend NFS link direct to Volantis – my 28TB storage server. This arrangement keeps the large file storage side of things off the web server disks & on a NAS, where it should be.
Extra RAM
First thing is a RAM upgrade to the full supported capacity of 16GB. This being a Proliant server machine, doesn’t take anything of a standard flavour, it’s requirements are DDR3-10600E or DDR3-12800E (the E in here being ECC). This memory is both eye-wateringly expensive & difficult to find anywhere in stock. It’s much cheaper & easier to find the ECC Registered variety, but alas this isn’t compatible.
Over the past 48 hours or so, I’ve been migrating everything over to the new baby server, with a couple of associated teething problems, but everything seems to have gone well so far. The remaining job to get everything running as it should is an external mail relay – sending any kind of email from a dynamic IP / domestic ISP usually gets it spam binned by the big providers instantly, regardless of it actually being spam or not – more to come on that setup & configuring postfix to use an external SMTP relay server soon!
If anyone does find something weird going on with the blog, do let me know via the contact page or comments!
As I mentioned in the previous post, these heaters have a standard interface that’s used for control & diagnostics, the W-Bus. This is transmitted over the K-Line of the vehicle bus, and all heaters, regardless of firmware modifications done by the various car manufacturers respond to this interface. Official Webasto diagnostic adaptors are available, but these are just a very expensive serial adaptor. A much cheaper option is a ~£5 Universal ODB adaptor.
ODB2
Above shows the signals on the ODB connector – the ones we’re interested in here are Pin 16, the +12v supply, and Pin 7, K-Line. Connect Pin 16 to the positive supply to the heater, and Pin 7 to Pin 2 on the Webasto heater. (Valid for all TT-V heaters).
Device Selection
Once these two connections are made to the heater, fire up the Thermo Test software. The screen above will be displayed. Pick W-Bus at top left.
COM Port Selection
First thing, connect the ODB adaptor to USB, and change to the correct COM port in Thermo Test. There may be several in the list, but a newly connected USB device should show up with the highest COM number.
Thermo Test
Once Thermo Test is running, start communications by going to the Diagnosis Menu > Start Diagnostic (F2 keyboard shortcut).
Initialized
After a few seconds, communication will be established. This will show faults, if any are present, and allow testing of the heater & it’s component parts. A summary report can be generated with Diagnosis > View Summary:
Diagnosis report Webasto Thermosystems
------------------------------------------------------------------------------------------
Configuration:
--------------
W-Bus version...............................................................3.3
Device name.............................................................X204 SH
W-Bus code.......................................................715CC0E73F8000
Fuel type................................................................Diesel
Circulating pump in control idle period.......................................0
Heating duration limitation.................................................255 [min]
Factor for shortening of ventilation duration...............................1/1
Device identification number..........................................09007236E
Dataset identification number.......................................09006806H05
Software identification number........................................000000000
HW version................................................................51/03
SW version..................................................Tuesday/07/04 12.12
SW version (EEPROM).........................................Tuesday/07/04 12.12
Date of manufacture control unit.......................................27.10.03
Date of manufacture heater.............................................04.02.04
Customer identification number.....................................4R8318K463AE
Serial number........................................................0000123626
Test signature.............................................................4B42
Minimum voltage threshold....................................................10 [V]
Maximum voltage threshold....................................................16 [V]
Delay for supply voltage min. detection......................................20 [s]
Delay for supply voltage max. detection.......................................6 [s]
Operating data:
---------------
Working hours.............................................................44:03 [h:m]
Operating hours.........................................................5388:08 [h:m]
Start count...............................................................19129
Burning duration PH 1..33%.................................................0:00 [h:m]
Burning duration PH 34..66%................................................0:00 [h:m]
Burning duration PH 67..100%...............................................0:00 [h:m]
Burning duration PH >100%..................................................0:00 [h:m]
Burning duration SH 1..33%.................................................0:00 [h:m]
Burning duration SH 34..66%................................................0:00 [h:m]
Burning duration SH 67..100%...............................................0:00 [h:m]
Burning duration SH >100%..................................................0:00 [h:m]
Working duration PH........................................................0:51 [h:m]
Working duration SH......................................................121:10 [h:m]
Start counter PH..............................................................6
Start counter SH............................................................854
Ventilation duration.......................................................0:00 [h:m]
Error:
------
------------------------------------------------------------------------------------------
12.03.17 17:17:30 Webasto Thermo Test 2.16.1
This shows all the important stuff, including running hours. (5388Hrs on this heater!). Most importantly, there are no faults listed.
Heater Running
The heater can be fully tested by issuing a start command from the Command Menu > Parking Heating option. Obviously cooling water will be required for this, along with an external water pump. (The water pump control output on these heaters seems to be totally disabled in firmware, as they rely on the engine’s coolant pump). I used a bucket of water along with a small centrifugal pump to provide the cooling. During this test I noted that the firmware is much more aggressive in these units. The marine versions shut down at ~72°C water temperature, whereas these don’t so the same until ~90°C.
Now I’ve managed to communicate with the heater, I’ll get onto building a standalone controller so I can dispense with the Windows VM for control.
Here’s another Diesel-fired heater related project – these Webasto heaters are fitted to Jaguar S-Type cars as auxiliary heaters, since (according to the Jag manual), the modern fuel-efficient diesels produce so little waste heat that extra help is required to run the car’s climate control system. (Although this seems to nullify any fuel efficiency boost, as the fuel saved by not producing so much waste heat in the engine itself is burned in an aux heater to provide heat anyway). The unfortunate part is these units don’t respond to applying +12v to Pin 1 of the ECU to get them to start – they are programmed to respond to CAN Bus & K-Line Bus only, so they require a bit more effort to get going. They also don’t have a built-in water circulation pump unlike the Webasto Thermo Top C heaters – they expect the water flow to be taken care of by the engine’s coolant pump.
Webasto LabelWater Side
The water ports are on the side of this heater instead of the end, the heat exhanger is on the left. These hearers are fitted to the car under the left front wing, behind a splash guard. Pretty easy to get to but they get exposed to all the road dirt, water & salt so corrosion is a little problem. The fuel dosing pump is in a much more difficult spot to get at – it’s under the car next to the fuel tank on the right hand side. Access to the underside with stands is required to get at this.
ECU Side
The ECU side has all the other connections – Combustion air, exhaust, fuel, power & control.
External Connectors
Only two of the external connectors are used on these heaters, the large two pin one is for main power – heavy cable required here as the current draw can climb to ~30A on startup while the glow plug fires. The 8-pin connector on the left is the control connector, where the CAN / K-Line / W-Bus buses live. The fuel dosing pump is also supplied from a pin on this connector. The small 3-pin under that is a blank for a circulation pump where fitted. Pinouts are here:
Pin
Signal
1
Battery Positive
2
Battery Negative
Pin Number
Signal
Notes
1
Telestart / Heater Enable
Would usually start the heater with a simple +12v ON signal, but is disabled in these heaters.
2
W-Bus / K-Line
Diagnostic Serial Bus Or Webasto Type 1533 Programmer / Clock
3
External Temp Sensor
4
CAN-
CAN Bus Low
5
Fuel Dosing Pump
Fuel Pump output. Connect pump to this pin & ground. Polarity unimportant.
6
Solenoid Valve
Fuel cutoff solenoid optionally fitted here.
7
CAN+
CAN Bus High
8
Cabin Heater Fan Control
This output switches on when heater reaches +50°C to control car heater blower
Pin
Signal
Notes
1
?
?
2
Circulation Pump +
3
Circulation Pump -
ECU Cover Removed
Removing the clipped-on plastic cover reveals the other ECU connectors. The large white one feeds the glow plug, & the large multi-pin below brings in the temp & overheat sensor signals.
MC9S12DT128B Microcontroller
The heart of the ECU is a massive microcontroller, a Freescale MC9S12DT128B, attached to a daughterboard hooked into the ECU power board.
Power Section
The high power section is on the board just under the connectors, here all the large semiconductors live for switching the fan motor, glow plug, external loads, etc.
LIN & CAN Bus Transceivers
The bus transceivers are separate ICs on the control board, a TJA1041 takes care of the CAN bus. There’s also a TJA1020 LIN bus transceiver here, which is confusing since none of the Webasto documentation mentions LIN bus control.
Combustion Fan Motor
The combustion fan motor is in the ECU compartment, nicely sealed away from the elements. There is no speed sensor on these blowers, unlike the Eberspacher ones.
Motor Details
The motor is a Buhler, rated at 10.5v.
Water Ports & Combustion Fan Cover
Unclipping the cover from the other end reveals the combustion fan, it’s under the black cover. (These are side-channel blowers, to provide the relatively high static pressure required to run the burner).
Sensor Clip
The overheat & temperature sensors are on the end of the heat exchanger, retained by a stainless clip.
Temp & Overheat Sensors
With the clip removed, the sensors can be seen better. There’s some pretty bad corrosion of the aluminium alloy on the end sensor, it’s seized in place.
Burner
The heater splits in half to reveal the evaporative burner itself. I’ve already cleaned the black crud off with a wire brush here, doesn’t look like this heater has seen much use as it’s pretty clean inside.
Burner Chamber
Inside the burner the fuel evaporates & is ignited. There is a brass mesh behind the backplate of the burner to assist with vaporisation.
Glow Plug
The glow plug is fitted into the side of the burner ceramic here. This is probably a Silicon Carbide device. It also acts as a flame sensor when the heater has fired up. The fuel inlet line is to the left under the clamp.
Heat Exhanger
The hot gases from the burner flow into the heat exchanger here, with many fins to increase the surface area. There’s only a couple of mm coating of carbon here, after 10 years on the car I would have expected it to be much more clogged.
I’m currently waiting on some components to build an interface so I can get the Webasto Thermo Test software to talk to the heater. Once this is done I can see if there are any faults logged that need sorting before I can get this heater running, but from the current state it seems to be pretty good visually. More to come once parts arrive!
The full service manual for these heaters can be grabbed from here, along with the wiring details for the Jaguar implementation & the Thermo Test software for talking to them:
I wrote a few weeks ago about replacing the hot water circulating pump on the boat with a new one, and mentioned that we’d been through several pumps over the years. After every replacement, autopsy of the pump has revealed the failure mode: the first pump failed due to old age & limited life of carbon brushes. The second failed due to thermal shock from an airlock in the system causing the boiler to go a bit nuts through lack of water flow. The ceramic rotor in this one just cracked.
The last pump though, was mechanically worn, the pump bearings nicely polished down just enough to cause the rotor to stick. This is caused by sediment in the system, which comes from corrosion in the various components of the system. Radiators & skin tanks are steel, engine block cast iron, back boiler stainless steel, Webasto heat exchanger aluminium, along with various bits of copper pipe & hose tying the system together.
The use of dissimilar metals in a system is not particularly advisable, but in the case of the boat, it’s unavoidable. The antifreeze in the water does have anti-corrosive additives, but we were still left with the problem of all the various oxides of iron floating around the system acting like an abrasive. To solve this problem without having to go to the trouble of doing a full system flush, we fitted a magnetic filter:
Mag Filter
This is just an empty container, with a powerful NdFeB magnet inserted into the centre. As the water flows in a spiral around the magnetic core, aided by the offset pipe connections, the magnet pulls all the magnetic oxides out of the water. it’s fitted into the circuit at the last radiator, where it’s accessible for the mandatory maintenance.
Sludge
Now the filter has been in about a month, I decided it would be a good time to see how much muck had been pulled out of the circuit. I was rather surprised to see a 1/2″ thick layer of sludge coating the magnetic core! The disgusting water in the bowl below was what drained out of the filter before the top was pulled. (The general colour of the water in the circuit isn’t this colour, I knocked some loose from the core of the filter while isolating it).
If all goes well, the level of sludge in the system will over time be reduced to a very low level, with the corrosion inhibitor helping things along. This should result in much fewer expensive pump replacements!
Here’s a chap eBay USB-To-Ethernet dongle I obtained for use with the Raspberry Pi Zero. This one is getting torn down permanently, as it’s rather unreliable. It seems to like having random fits where it’ll not enumerate on the USB bus. The silicon in the ICs will eventually make it here once I manage to get a new microscope 😉
Main Chipset
This is quite a heavily packed PCB, with the main Asix AX88178 on the left. This IC contains all of the logic for implementing the Ethernet link over USB, except the PHY. It’s clock crystal is in the top left corner.
Reverse Side
Not much on the reverse side, there’s a 3.3v linear regulator at top left, the SOIC is an Atmel AT93C66A 4KB EEPROM for configuration data.
Vitesse PHY
The final IC in the chain is the Vitesse VSC8211 Gigabit PHY, with it’s clock crystal below. This interfaces the Ethernet MAC in the Asix IC to the magjack on the right.
This is a cheap little eBay reader to replace my ~10 year old multi-reader that very recently died. My original was an 8-in-1 version, but as I never read anything else other than SD cards these days, a little USB dongle version was more convenient.
Controller Chipset
The layout is very minimal, just the µSD socket, bypass passives & the main controller chip on this side, which is a GL3224 Dual LUN Memory Card Controller from Genesys Logic. This is fully USB3 capable according to the datasheet, but I’m not certain of the advantage of this for something that reads relatively slow devices like SD cards.
SD Socket
The other side of the PCB holds the full size SD socket, along with the activity LED & USB connector.
Having been a user of ownCloud for a long while, I decided to jump ship to the fork NextCloud for a few reasons, but the main one is that I never managed to get ownCloud to update itself (with the built-in updater app in the Admin panel) without completely shitting the bed, and as a result having to start from scratch & reupload all my files.
Nextcloud on the other hand has managed a major upgrade without any such problems, and the developers seem to be much more active than the ownCloud devs at present.
The one issue at the moment is that there are no packages for the Linux desktop client – it has to be built from scratch. This isn’t too difficult though, but to make things even easier I’ve thrown together a little bash script to automate the process. It’s tested to work under the latest version of Linux Mint (18.1), and does use a couple of commands that sudo won’t allow, so has to be run as root. It’s not polished in any way, but does work fine!
After the build process has completed, the client itself can be run from the Terminal, or made to run at system boot via the Startup Applications Editor in Linux Mint.
#!/bin/bash
echo "This script will compile & install Nextcloud Desktop Sync Client"
echo "Please be patient, this will take a while"
if [[ $EUID -ne 0 ]]; then
echo "Root commands are used by this script, please run as root user to avoid errors"
exit 1
fi
echo ""
echo "Installing Build Tools..."
echo ""
apt-get install cmake git-core -y
echo ""
echo "Cloning GitHub Repo..."
echo ""
git clone https://github.com/nextcloud/client_theming.git
cd client_theming
git submodule update --init --recursive
echo ""
echo "Adding Xenial Source Repos to /etc/apt/sources.list..."
echo ""
echo "deb-src http://archive.ubuntu.com/ubuntu/ xenial universe" >> /etc/apt/sources.list
echo "deb-src http://archive.ubuntu.com/ubuntu/ xenial-updates universe" >> /etc/apt/sources.list
echo ""
echo "Updating Apt & installing build dependencies..."
echo ""
apt-get update
apt build-dep owncloud-client -y
echo ""
echo "Compiling NextCloud Client..."
echo ""
mkdir build-linux
cd build-linux
cmake -D OEM_THEME_DIR=`pwd`/../nextcloudtheme ../client
make
make install
echo ""
echo "Adding Custom Library Directory Config..."
echo ""
echo "/usr/local/lib/x86_64-linux-gnu" >> /etc/ld.so.conf.d/x86_64-linux-gnu.conf
ldconfig
echo ""
echo "Nextcloud Client has been built & installed!"
echo ""
exit 0
After having a couple of the cheap Chinese PSUs fail on me in a rather spectacular fashion, I decided to splash on a more expensive name-brand PSU, since constantly replacing PSUs at £15 a piece is going to get old pretty fast. This is the 30A model from Mercury, which seems to be pretty well built. It’s also significantly more expensive at £80. Power output is via the beefy binding posts on the front panel. There isn’t any metering on board, this is something I’ll probably change once I’ve ascertained it’s reliability. This is also a fixed voltage supply, at 13.8v.
Rear Panel
Not much on the rear panel, just the fuse & cooling fan. This isn’t temperature controlled, but it’s not loud. No IEC power socket here, the mains cable is hard wired.
Main Board
Removing some spanner-type security screws reveals the power supply board itself. Everything on here is enormous to handle the 30A output current at 13.8v. The main primary side switching transistors are on the large silver heatsink in the centre of the board, feeding the huge ferrite transformer on the right.
Transformer
The transformer’s low voltage output tap comes straight out instead of being on pins, due to the size of the winding cores. Four massive diodes are mounted on the black heatsinks for output rectification.
SMPS Controller
The supply is controlled via the jelly bean TL494 PWM controller IC. The multi-turn potentiometer doesn’t adjust the output voltage, more likely it adjusts the current limit.
Standby Supply
Power to initially start the supply is provided by a small SMPS circuit, with a VIPer22A Low Power Primary Switcher & small transformer on the lower right. The transformer upper left is the base drive transformer for the main high power supply.
In a word, no they aren’t any good. As usual, cheap doesn’t equal good, and in this case the cheapo clones are a total waste of money. Read on for the details!
I’ve been looking into using a cheap Chinese clone Honda GX35 engine to drive an automotive alternator as a portable battery charging & power unit. These engines are available very cheaply on eBay, aimed at the mini-bike/go-kart market.
For those not in the know, the Honda GX25/35 4-strokes are strimmer-type engines that traditionally were always of 2-stroke construction. Honda worked out how to have a wet-sump engine without the need to keep the engine always in the “upright” position. They do not require mixing of oil into the fuel for lubrication as 2-strokes do, so should be much cleaner running.
So far I’ve had two of these cheap engines, as the first one died after only 4 hours run time, having entirely lost compression. At the time the engine was idling, no load, having been started from cold only a few minutes before. Having checked the valve clearances to make sure a valve wasn’t being held partially open, I deduced that the cause was broken piston rings. This engine was replaced by the seller, so I didn’t get a chance to pull it to bits to find out, but I decided to do a full teardown on the replacement to see where the cloners have cut corners.
Oil Return Hose
I’ve already stripped off the ancillary components: exhaust, carburettor, fuel tank, cowlings, as these parts are standard to any strimmer engine. The large black hose here is the oil return feed back to the rocker cover from the crankcase. The oiling system in these engines is rather clever. The main engine block is made of light alloy, probably some permutation of Aluminium. There is much flashing left behind between the cylinder fins from the die-casting process, and not a single engine manufacturer’s logo anywhere. (From what I’ve read, the genuine Honda ones have their logo on the side of the crankcase).
Rocker Box
Here’s the top of the engine with valves, rockers & camshaft. All the valve gear up here, minus the valves themselves & springs, are manufactured from sintered steel, there are no proper “bearings”, the steel shafts just run in the aluminium castings. The cam gear is of plastic, with the sintered steel cam pressed into place. The cam also has the bearing surface for the pin that the whole assembly rotates on. The timing belt runs in the oil & is supposed to last the life of the engine, and while I’d believe that in the original Honda, I certainly wouldn’t in this engine. The black grommet is the opening of the oil return gallery.
Cam
Here’s the cam on the back of the plastic pulley. A single cam is used for both intake & exhaust valves for space & simplicity.
Intake Valve Stem Seal
Just visible under the intake valve spring is a simple stem seal, to hopefully prevent oil being sucked down the valve guide into the cylinder by intake vacuum. Running these cheap engines proves this seal to be ineffective, as they blow about as much blue oil smoke as a 2-stroke when they’re started cold. 😉
Starter Side
The starter side is where the oil sump is located on these engines, along with the dipstick.
Flywheel Side
The flywheel end of the engine is the usual fare for small engines. Ignition is provided by a magneto, with a magnet in the flywheel. This is no different from the 2-stroke versions. As these ignitions fire on every revolution of the crankshaft, the spark plug fires both on compression, igniting the fuel for normal operation, and again into the exhaust stroke, where the spark is wasted.
One thing I have noticed about these engines is an almost total lack of cooling air coming through the cowling over the cylinder cooling fins. Plenty was flowing over the exhaust silencer side, I believe bad housing design would be what causes this problem. A lack of cooling certainly wouldn’t help engine longevity!
Engine “Sump”
Separating the bottom of the engine was a little difficult, as there is a significant bead of sealant used instead of a gasket. Inside the sump of the engine are a pair of paddles, which stir up the oil into a mist. As the piston moves in the cylinder, it acts as a pump, creating alternating pulses of pressure & vacuum in the crankcase. Oil mist flows through a drilling in the crank from the sump, into the crankcase where it (hopefully) lubricates the bearings & the cylinder wall. Incidentally, the only main bearings are on the crankcase – the far end of the shaft that carries the oil paddles & timing belt is just flapping in the breeze, the only support being the oil seal in the outer housing. The crank itself isn’t hardened – a file easily removes metal from all parts that I could get at. The big end journal pin might be, but these cranks are pressed together so I can’t access that part.
Lubrication Gallery
The oil mist feeds into the crankcase through this hollow section of shaft, there’s a drilling next to the timing belt pulley to connect the two spaces together.
Lower Crankcase
The lower crankcase is just a simple die casting, there’s a check valve at the bottom under the crankshaft to transfer oil to the rocker cover, through the rubber tube on the outside of the engine. After the oil reaches the rocker box, it condenses & returns to the sump via the timing belt cavity.
Piston Crown
Removing the crankshaft from the engine block gives me a look at the piston. The factory couldn’t even be arsed to machine the crown, it’s still got the rough finish from the hot-forging press. This bad finish will pick up much carbon from combustion, and would probably cause detonation once enough had accumulated to become incandescent in the heat of combustion. Only the centre is machined, just enough for them to stamp a number on.
Cylinder Bore
A look up the cylinder bore shows the valves in the cylinder head. These engines, like their 2-stroke cousins have a single casting instead of a separate block & head, so getting at the valves is a little more of a pain. The cylinder bore itself is a cast-in iron liner and it’s totally smooth – like a mirror finish. There’s not a single sign of a crosshatch pattern from honing. If the first engine that died on me was the same – I’d be surprised if it wasn’t, this could easily cause ring breakage. The usual crosshatch pattern the cylinder hone produces holds oil, to better help lubricate the piston & rings. Without sufficient lubrication, the rings will overheat & expand far enough to close the end gap. Once this happens they will break.
Engine Valves
Finally, here’s the valves with their springs removed from the cylinder. These are the smallest poppet valves I’ve ever seen, a British penny is provided for scale.
In all, these engines share many components with the older 2-stroke versions. The basic crankshaft & connecting rod setup is the same as I’ve seen in many old 2-strokes previous, the addition of the rather ingenious oiling system by Honda is what makes these tiny 4-strokes possible. I definitely won’t be trusting these very cheap copies in any of my projects, reliability is questionable at the least. The apparent lack of cooling air flow over the cylinder from the flywheel fan is concerning, along with the corner-cutting on the cylinder finishing process & piston crown, presumably to reduce factory costs.
The other day I was given a random pile of car electronic parts from the scrap bin at the local garage, so I decided to do a few teardowns. This first one is a Temic Central Locking / Immobiliser module from a Mercedes van. Judging by the 125kHz stamped on the label, this also has RFID capability.
PCB
The casing just unclips, revealing the PCB. Surprisingly for an automotive module, there is no conformal coating on this (they’re usually heavily coated in protective lacquer to prevent moisture ingress).
Microcontroller
The large IC from Motorola I’m assuming to be a microcontroller, but I didn’t manage to find anything from the markings. There’s not much else in here apart from some glue logic, and what I think is the 125Khz toroidal antenna in the top left corner.
My new DMM I posted about a while back came with PC software & drivers for the RS-232 interface, on a CD. I haven’t used CDs for some time, so I had to dig out my USB drive.
The Tenma website doesn’t list the software for all their models, so to help others I’m posting an archive of all the supplied drivers here. The archive contains software & drivers for the following Tenma models:
Here’s another random gadget for teardown, this time an IR remote control repeater module. These would be used where you need to operate a DVD player, set top box, etc in another room from the TV that you happen to be watching. An IR receiver sends it’s signal down to the repeater box, which then drives IR LEDs to repeat the signal.
Repeater Module
Not much to day about the exterior of this module, the IR input is on the left, up to 3 receivers can be connected. The outputs are on the right, up to 6 repeater LEDs can be plugged in. Connections are done through standard 3.5mm jacks.
Repeater PCB
Not much inside this one at all, there are 6 transistors which each drive an LED output. This “dumb” configuration keeps things very simple, no signal processing has to be done. Power is either provided by a 12v input, which is fed into a 7805 linear regulator, or direct from USB.
For some time now I’ve been running a large disk array to store all the essential data for my network. The current setup has 10x 4TB disks in a RAID6 array under Linux MD.
Up until now the disks have been running in external Orico 9558U3 USB3 drive bays, through a PCIe x1 USB3 controller. However in this configuration there have been a few issues:
Congestion over the USB3 link. RAID rebuild speeds were severely limited to ~20MB/s in the event of a failure. General data transfer was equally as slow.
Drive dock general reliability. The drive bays are running a USB3 – SATA controller with a port expander, a single drive failure would cause the controller to reset all disks on it’s bus. Instead of losing a single disk in the array, 5 would disappear at the same time.
Cooling. The factory fitted fans in these bays are total crap – and very difficult to get at to change. A fan failure quickly allows the disks to heat up to temperatures that would cause failure.
Upgrade options difficult. These bays are pretty expensive for what they are, and adding more disks to the USB3 bus would likely strangle the bandwidth even further.
Disk failure difficult to locate. The USB3 interface doesn’t pass on the disk serial number to the host OS, so working out which disk has actually failed is difficult.
To remedy these issues, a proper SATA controller solution was required. Proper hardware RAID controllers are incredibly expensive, so they’re out of the question, and since I’m already using Linux MD RAID, I didn’t need a hardware controller anyway.
16-Port HBA
A quick search for suitable HBA cards showed me the IOCrest 16-port SATAIII controller, which is pretty low cost at £140. This card breaks out the SATA ports into standard SFF-8086 connectors, with 4 ports on each. Importantly the cables to convert from these server-grade connectors to standard SATA are supplied, as they’re pretty expensive on their own (£25 each).
This card gives me the option to expand the array to 16 disks eventually, although the active array will probably be kept at 14 disks with 2 hot spares, this will give a total capacity of 48TB.
SATA HBA
Here’s the card installed in the host machine, with the array running. One thing I didn’t expect was the card to be crusted with activity LEDs. There appears to be one LED for each pair of disks, plus a couple others which I would expect are activity on the backhaul link to PCIe. (I can’t be certain, as there isn’t any proper documentation anywhere for this card. It certainly didn’t come with any ;)).
I’m not too impressed with the fan that’s on the card – it’s a crap sleeve bearing type, so I’ll be keeping a close eye on this for failure & will replace with a high quality ball-bearing fan when it finally croaks. The heatsink is definitely oversized for the job, with nothing installed above the card barely gets warm, which is definitely a good thing for life expectancy.
Update 10/02/17 – The stock fan is now dead as a doornail after only 4 months of continuous operation. Replaced with a high quality ball-bearing 80mm Delta fan to keep things running cool. As there is no speed sense line on the stock fan, the only way to tell it was failing was by the horrendous screeching noise of the failing bearings.
SCSI Controller
Above is the final HBA installed in the PCIe x1 slot above – a parallel SCSI U320 card that handles the tape backup drives. This card is very close to the cooling fan of the SATA card, and does make it run warmer, but not excessively warm. Unfortunately the card is too long for the other PCIe socket – it fouls on the DIMM slots.
Backup Drives
The tape drives are LTO2 300/600GB for large file backup & DDS4 20/40GB DAT for smaller stuff. These were had cheap on eBay, with a load of tapes. Newer LTO drives aren’t an option due to cost.
The main disk array is currently built as 9 disks in service with a single hot spare, in case of disk failure, this gives a total size after parity of 28TB:
/dev/md0:
Version : 1.2
Creation Time : Wed Mar 11 16:01:01 2015
Raid Level : raid6
Array Size : 27348211520 (26081.29 GiB 28004.57 GB)
Used Dev Size : 3906887360 (3725.90 GiB 4000.65 GB)
Raid Devices : 9
Total Devices : 10
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Mon Nov 14 14:28:59 2016
State : active
Active Devices : 9
Working Devices : 10
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 64K
Name : Main-PC:0
UUID : 266632b8:2a8a3dd3:33ce0366:0b35fad9
Events : 773938
Number Major Minor RaidDevice State
0 8 48 0 active sync /dev/sdd
1 8 32 1 active sync /dev/sdc
9 8 96 2 active sync /dev/sdg
10 8 112 3 active sync /dev/sdh
11 8 16 4 active sync /dev/sdb
5 8 176 5 active sync /dev/sdl
6 8 144 6 active sync /dev/sdj
7 8 160 7 active sync /dev/sdk
8 8 128 8 active sync /dev/sdi
12 8 0 - spare /dev/sda
The disks used are Seagate ST4000DM000 Desktop HDDs, which at this point have ~15K hours on them, and show no signs of impending failure.
USB3 Speeds
Here’s a screenshot with the disk array fully loaded running over USB3. The aggregate speed on the md0 device is only 21795KB/s. Extremely slow indeed.
This card is structured similarly to the external USB3 bays – a PCI Express bridge glues 4 Marvell 9215 4-port SATA controllers into a single x8 card. Bus contention may become an issue with all 16 ports used, but as far with 9 active devices, the performance increase is impressive. Adding another disk to the active array would certainly give everything a workout, as rebuilding with an extra disk will hammer both read from the existing disks & will write to the new.
HBA Speeds
With all disks on the new controller, I’m sustaining read speeds of 180MB/s. (Pulling data off over the network). Write speeds are always going to be pretty pathetic with RAID6, as parity calculations have to be done. With Linux MD, this is done by the host CPU, which is currently a Core2Duo E7500 at 2.96GHz, with this setup, I get 40-60MB/s writes to the array with large files.
Disk Array
Since I don’t have a suitable case with built in drive bays, (again, they’re expensive), I’ve had to improvise with some steel strip to hold the disks in a stack. 3 DC-DC converters provides the regulated 12v & 5v for the disks from the main unregulated 12v system supply. Both the host system & the disks run from my central battery-backed 12v system, which acts like a large UPS for this.
The SATA power splitters were custom made, the connectors are Molex 67926-0001 IDC SATA power connectors, with 18AWG cable to provide the power to 4 disks in a string.
IDT Insertion Tool
These require the use of a special tool if you value your sanity, which is a bit on the expensive side at £25+VAT, but doing it without is very difficult. You get a very well made tool for the price though, the handle is anodised aluminium & the tool head itself is a 300 series stainless steel.
Here’s a useful tool for testing both power supplies & batteries, a dummy load. This unit is rated up to 60W, at voltages from 1v to 25v, current from 200mA to 9.99A.
This device requires a 12v DC power source separate from the load itself, to power the logic circuitry.
Microcontroller Section
Like many of these modules, the brains of the operation is an STM8 microcontroller. There’s a header to the left with some communication pins, the T pin transmits the voltage when the unit is operating, along with the status via RS232 115200 8N1. This serial signal is only present in DC load mode, the pin is pulled low in battery test mode. The 4 pins underneath the clock crystal are the programming pins for the STM8.
Serial CommsCooling Fan
The main heatsink is fan cooled, the speed is PWM controlled via the microcontroller depending on the temperature.
Main MOSFET
The main load MOSFET is an IRFP150N from Infineon. This device is rated at 100v 42A, with a max power dissipation of 160W. On the right is a dual diode for reverse polarity protection, this is in series with the MOSFET. On the left is the thermistor for controlling fan speed.
Load Terminals
The load is usually connected via a rising clamp terminal block. I’ve replaced it with a XT60 connector in this case as all my battery holders are fitted with these. This also removes the contact resistance of more connections for an adaptor cable. The small JST XH2 connector on the left is for remote voltage sensing. This is used for 4-wire measurements.
Function 1 – DC Load
Powering the device up while holding the RUN button gets you into the menu to select the operating modes. Function 1 is simple DC load.
Function 2 – Battery Capacity Mode
The rotary encoder is used to select the option. Function 2 is battery capacity test mode.
Beeper Mode
After the mode is selected, an option appears to either turn the beeper on or off.
Amps Set
When in standby mode, the threshold voltage & the load current can be set. Here the Amps LED is lit, so the load current can be set. The pair of LEDs between the displays shows which digit will be changed. Pressing the encoder button cycles through the options.
Volts Set
With the Volts LED lit, the threshold voltage can be changed.
When in DC load mode (Fun1), the device will place a fixed load onto the power source until it’s manually stopped. The voltage setting in this mode is a low-voltage alarm. The current can be changed while the load is running.
When in battery discharge test mode (Fun2), the voltage set is the cutoff voltage – discharge will stop when this is reached. Like the DC load mode, the current can be changed when the load is running. After the battery has completed discharging, the capacity in Ah & Wh will be displayed on the top 7-segment. These results can be selected between with the encoder.
Below are tables with all the options for the unit, along with the error codes I’ve been able to decipher from the Chinese info available in various places online. (If anyone knows better, do let me know!).
Option
Function
Fun1
Basic DC Load
Fun 2
Battery Capacity Test
BeOn
Beeper On
BeOf
Beeper Off
Error Code
Meaning
Err1
Input Overvoltage
Err2
Low Battery Voltage / No Battery Present / Reverse Polarity
Err3
Battery ESR Too High / Cannot sustain selected discharge current
Err4
General Failure
Err6
Power Supply Voltage Too Low / Too High. Minimum 12v 0.5A.
To do some upgrades to my NAS, I needed some SATA power adaptors, to split the PSU out to the planned 16 disk drives. eBay has these for very little money, however there’s a good reason for them being cheap.
Wire Marking
The marking on the wire tells me it’s 18AWG, which should be good for 9.5A at an absolute maximum. However these adaptors are extremely light.
Wire Comparison
Here’s the cheapo eBay wire compared to proper 18AWG wire. The cores in the eBay adaptor are tiny, I’d guess about 24AWG, only good for about 3A. As disk drives pull about 2A from the +12v rail on startup to spin the platters up to speed, this thin wire is going to cause quite the volt drop & possibly prevent the disk from operating correctly.
Well it’s time for a new DMM. After the last pair of eBay El-Cheapo Chinese meters just didn’t last very well, I decided a proper meter was required. This one is a Tenma 72-10405, stocked by Farnell for under £60. Not quite as many festures as the cheapo Chinese meters, but I expect this one to be a bit more reliable.
PCB Rear
Since I can’t have anything without seeing how it’s put together, here’s the inside of the DMM. (Fuse access is only possible by taking the back cover off as well. The 9v PP3 battery has a seperate cover).
PCB Rear Bottom
He’s the input section of the meter, with the 10A HRC fuse & current shunt for the high-amps range. The other fuse above is for the mA/µA ranges. The back cover has a wide lip around the edge, that slots into a recess in the front cover, presumably for blast protection if the meter should meet a sticky end. The HRC fuses are a definite improvement over the cheap DMMs, they only have 15mm glass fuses, and no blast protection built into the casing.
There are some MOVs for input protection on the volts/ohms jack, the jacks themselves are nothing more than stampings though.
PCB Rear Top
Not much at the other side of the board, there’s the IR LED for the RS232 interface & the beeper.
PCB Front
Most of the other components are on the other side of the PCB under the LCD display. The range switch is in the centre, while the main chipset is on the left.
DMM Chipset
The chipset of this meter is a FS9922-DMM3 from Fortune Semiconductor, this is a dedicated DMM chipset with built in ADCs & microcontroller.
As one of my current projects involves a small petrol engine – a Honda GX35 clone, I figured an hour counter would be very handy to keep an eye on service intervals. (More to come on the engine itself later on). I found a device that would suit my needs on good old eBay.
Inductive Engine Monitor
These engine monitors are pretty cheap, at about £4. The sensing is done by a single heat-resistant silicone wire, that wraps around the HT lead to the spark plug. The unit can be set for different firing intervals via the buttons. In the case of most single-cylinder 4-stroke engines, the spark plug fires on every revolution – wasted-spark ignition. This simplifies the ignition system greatly, by not requiring the timing signal be driven from 1/2 crankshaft speed. The second “wasted” spark fires into the exhaust stroke, so has no effect.
Internals
The back cover is lightly glued into place with a drop of cyanoacrylate in opposite corners, but easily pops off. The power is supplied by a soldered-in 3v Lithium cell. The main microcontroller has no number laser etched on to it at all – it appears it skipped the marking machine.
Input Filtering
The input from the sensing wire comes in through a coupling capacitor & is amplified by a transistor. It’s then fed into a 74HC00D Quad 2-Input NAND gate, before being fed into the microcontroller.
Pickup
The pickup wire is simply wound around the spark plug lead. I’ve held it in position here with some heatshrink tubing. Heat in this area shouldn’t be an issue as it’s directly in the airflow from the flywheel fan.
Time foe some more retro tech! This is a 1980’s vintage CCD-based VHS camcorder from Panasonic, the NV-M5. There are a lot of parts to one of these (unlike modern cameras), so I’ll split this post into several sections to make things easier to read (and easier to keep track of what I’m talking about :)).
Left Side
The left side of the camera holds the autofocus, white balance, shutter speed & date controls.
Left Side ControlsLens Adjustments
The lens is fully adjustable, with either manual or motorized automatic control.
Rear Panel
The back panel has the battery slot, a very strange looking DC input connector, remote control connector & the earphone jack.
Top Controls
The top panel of the camera holds the main power controls, manual tape tracking & the tape transport control panel.
Viewfinder
The viewfinder is mounted on a swivel mount. There’s a CRT based composite monitor in here. Hack ahoy!
Camera Section
Process Board Assembly
Here’s the camera section of the camcorder, and is totally packed with electronics! There’s at least half a dozen separate boards in here, all fitted together around the optics tube assembly.
AWB PCB
On the top of the assembly is the Automatic White Balance PCB. Many adjustments here to get everything set right. Not much on the other side of this board other than a bunch of Op-Amps. The iris stepper motor is fitted in a milled opening in the PCB, this connects to one of the other PCBs in the camera module.
AWB Sensor
Here’s the AWB sensor, mounted next to the lens. I’m not all to certain how this works, but the service manual has the pinout, and there are outputs for all the colour channels, RGB. So it’s probably a trio of photodiodes with filters.
Focus & Zoom Motors
Focus & Zoom are controlled with a pair of DC gear motors. The manual operation is feasible through the use of slip clutches in the final drive pinion onto the lens barrel.
Process Board
The main camera section process board is above. This board does all the signal processing for the CCD, has the bias voltage supplies and houses the control sections for the motorized parts of the optics assembly. There are quite a few dipped Tantalum capacitors on pigtails, instead of being directly board mounted. This was probably done due to space requirements on the PCB itself.
Under the steel shield on this board is some of the main signal processing for the CCD.
Optics Assembly
The back of the optics tube is a heavy casting, to supress vibration. This will be more clear later on.
Position Sensor Flex
The position of the lens elements is determined by reflective strips on the barrel & sensors on this flex PCB.
Sub Process Board
There’s another small board tucked into the side of the tube, this hooks into the process PCB.
Process Delay Line
According to the schematic, there’s nothing much on this board, just a delay line & a few transistors.
Piezo Focus Disc
Here’s the reason for the heavy alloy casing at the CCD mounting end of the optics: the fine focus adjustment is done with a piezoelectric disc, the entire CCD assembly is mounted to this board. Applying voltage to the electrodes moves the assembly slightly to alter the position of the CCD. The blue glass in the centre of the unit is the IR filter.
IR Relective Sensors
The barrel position sensors are these IR-reflective type.
Iris Assembly
The iris is mounted just before the CCD, this is controlled with a galvanometer-type device with position sensors incorporated.
Iris Opening
Pushing on the operating lever with the end of my screwdriver opens the leaves of the iris against the return spring.
Tape Transport & Main Control
Main Control Board
Tucked into the side of the main body of the unit is the main system control board. This PCB houses all the vital functions of the camera: Power Supply, Servo Control, Colour Control,Video Amplifiers, etc.
Tape Drum
Here’s the main tape transport mechanism, this is made of steel & aluminium stampings for structural support. The drum used in this transport is noticeably smaller than a standard VHS drum, the tape is wrapped around more of the drum surface to compensate.
Tape Transport
The VHS tape sits in this carriage & the spools drive the supply & take up reels in the cartridge.
Main Control PCB
Here’s the component side of the main control PCB. This one is very densely packed with parts, I wouldn’t like to try & troubleshoot something like this!
Main PCB Left
The left side has the video head amp at the top, a Panasonic AN3311K 4-head video amp. Below that is video processing, the blue components are the analogue delay lines. There are a couple of hybrid flat-flex PCBs tucked in between with a couple of ICs & many passives. These hybrids handle the luma & chroma signals.
Top left is the capstan motor driver a Rohm BA6430S. The transport motors are all 3-phase brushless, with exception of the loading motor, which is a brushed DC type.
Delay Line
Here’s what is inside the delay lines for the analogue video circuits. The plastic casing holds a felt liner, inside which is the delay line itself.
Internal Glass
The delay is created by sending an acoustic signal through the quartz crystal inside the device by a piezoelectric transducer, bouncing it off the walls of the crystal before returning it to a similar transducer.
Main PCB Centre
Here’s the centre of the board, the strange crystal at bottom centre is the clock crystal for the head drum servo. Why it has 3 pins I’m not sure, only the two pins to the crystal inside are shown connected on the schematic. Maybe grounding the case?
The main servo controls for the head drum & the capstan motor are top centre, these get a control signal from the tape to lock the speed of the relative components.
Main PCB Right
Here’s the right hand side. The main power supply circuitry is at top right, with a large can containing 4 switching inductors & a ferrite pot core transformer. All these converters are controlled by a single BA6149 6-channel DC-DC converter controller IC via a ULN2003 transistor array.
The ceramic hybrid board next to the PSU has 7 switch transistors for driving various indicator LEDs.
The large tabbed IC bottom centre is the loading motor drive, an IC from Mitsubishi, the M54543. This has bidirectional DC control of the motor & built in braking functions. The large quad flat pack IC on the right is the MN1237A on-screen character generator, with the two clock crystals for the main microcontroller.
Erase Head
The full erase head has it’s power supply & oscillator on board, applying 9v to this board results in an AC signal to the head, which erases the old recording from the tape before the new recording is laid down by the flying heads on the drum.
Audio Control PCB
The Audio & Control head is connected to this PCB, which handles both reading back audio from the tape & recording new audio tracks. The audio bias oscillator is on this board, & the onboard microphone feeds it’s signal here. The control head is fed directly through to the servo section of the main board.
Drum Motor
The motor that drives the head drum is another DC brushless 3-phase type.
Hall Sensors
These 3 Hall sensors are used by the motor drive to determine the rotor position & time commutation accordingly.
Stator
The stator on this motor is of interesting construction, with no laminated core, the coils are moulded into the plastic holder. The tach sensor is on the side of the stator core. This senses a small magnet on the outside of the rotor to determine rotational speed. For PAL recordings, the drum rotates at 1500 RPM.
Motor Removed
Not much under the stator other than the bearing housing & the feedthrough to the rotary transformer.
Head Disc
The heads are mounted onto the top disc of the drum, 4 heads in this recorder. The signals are transmitted to the rotating section through the ferrite rotary transformer on the bottom section.
Head Chip
The tiny winding of the ferrite video head can just about be seen on the end of the brass mounting.
Capstan Motor Components
The capstan motor is similar to the drum motor, only this one is flat. The rotor has a ferrite magnet, in this case it wasn’t glued in place, just held by it’s magnetic field.
Capstan Motor Stator
The PCB on this motor has a steel backing to complete the magnetic circuit, the coils for the 3 motor phases are simply glued in place. The Hall sensors on this motor are placed in the middle of the windings though.
Again there is a tach sensor on the edge of the board that communicates the speed back to the controller. This allows the servo to remain locked at constant speed.
Viewfinder
Viewfinder Assembly
As usual with these cameras, this section is the CRT based viewfinder. These units take the composite signal from the camera to display the scene. This one has many more pins than the usual viewfinder. I’ll hack a manual input into this, but I’ll leave that for another post.
Viewfinder Circuits
Being an older camera than the ones I’ve had before, this one is on a pair of PCBs, which are both single-sided.
Main Viewfinder Board
The main board has all the power components for driving the CRT & some of the adjustments. The main HV flyback transformer is on the right. This part creates both the final anode voltage for the tube & the focus/grid voltages.
Viewfinder Control PCB Top
The viewfinder control IC is on a separate daughter board in this camera, with two more controls.
Control IC
The control IC is a Matsushita AN2510S, this has all the logic required to separate the sync pulses from the composite signal & generate an image on the CRT.
Viewfinder CRT Frame
The recording indicator LEDs are mounted in the frame of the CRT & appear above the image in the viewfinder.
Viewfinder CRT With Yoke
Here the CRT has been separated from the rest of the circuitry with just the deflection yoke still attached.
M01JPG5WB CRT
The electron gun in this viewfinder CRT is massive in comparison to the others that I have seen, and the neck of the tube is also much wider. These old tubes were very well manufactured.
Viewfinder Optics
A simple mirror & magnifying lens completes the viewfinder unit.
Here’s a small flyback / Line Output Transformer from a portable colour TV set. Usually these transformers are vacuum potted in hard epoxy resin & are impossible to disassemble without anything short of explosives. (There are chemical means of digesting cured epoxies, but none of them are pleasant). This one however, was potted in silicone, so with some digging, the structure of the transformer can be revealed.
Cap Removed
The cap was glued on to the casing, but this popped off easily. The top of the core is visible in the silicone potting material.
The Digging Starts
A small screwdriver was used to remove the potting material, while trying not to damage the winding bobbin & core too badly. The bulge in the casing that I originally thought might house a voltage multiplier turns out to be totally empty. The white plastic bobbin is becoming visible around the core.
Bobbin
After some more digging & a lot of mess later, the entire transformer is revealed. The primary & auxiliary secondaries are visible at the bottom of the transformer, next to the pins. These transformers have multiple windings, as they’re used not only for supplying the final anode voltage of several Kilovolts to the CRT, but many of the other associated voltages, for the heater, grids, focus electrodes, etc. These lower voltage windings are on the same part of the core as the primary.
Above those is the main high voltage secondary winding, which looks to be wound with #38-#40AWG wire (about the thinnest available, at 0.07mm diameter. This is wound in many sections of of a few hundred turns each to increase the insulation resistance to the high voltage. The main anode wire emerges from the top of the bobbin.
Output Rectifier
Hidden in a recess at the top is the main HV rectifier, which on this small transformer is a single device (it’s probably not internally, most likely a series stack of diodes to get the PIV rating required).
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