Another decapped IC! This one is an ST L6219 750mA stepper motor driver. The control logic is all at the bottom of the die, with the high current H-Bridge transistors at the top.
IC Decap – ST Micro L6219 Stepper Motor Driver
Author: The Engineer
IC Decap – Analog Devices AD8403 Digital Potentiometer
Here’s another die photo from the collection, this time it’s a 512-step digital pot from Analog devices.
nb Tanya Louise Heating System – Oxide Sludge
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:
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.
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!
AIX Gigabit Ethernet To USB Bridge
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 😉
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.
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.
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.
USB3 SD/µSD Card Reader Teardown
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.
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.
The other side of the PCB holds the full size SD socket, along with the activity LED & USB connector.
DIY Eberspacher Glowplug Screens: The Test Of Time
Some time ago I did a couple of posts on cheapening up the maintenance of Eberspacher hot air heaters by making the glow plug screens myself. Now one of my pieces of stainless mesh has been in the heater for nearly a year, and the heater is starting to get a bit smoky on a cold start. This is usually a sign that the screen isn’t allowing the fuel to vaporise quick enough for the glow plug to ignite the flame, because it’s becoming blocked. So far the heater has had about 150L of diesel through it with my DIY screen.
After removing the plug, here’s what’s left of the screen. The bottom end has completely disintegrated, but this is to be expected – OEM screens do the same thing as this end is exposed to the most heat in the burner. There’s quite a bit of coke buildup on the top end of the screen around the fuel nozzle, again this isn’t surprising, as this is the coolest part of the heater not all the heavier fractions of the diesel fuel have the chance to vaporise.
Looking further down into the mixing tube of the main burner, everything looks good. There’s a coating of soot in there, but no tar-like build up that would tell me the unit isn’t burning properly. Another advantage of making my own screens is that they’re much easier to extract from the hole once they’ve been in there for months. The OEM screens have a stainless ring spot welded to the mesh itself to hold it’s shape, and once there’s enough fuel residue built up the entire mess seizes in place, requiring some sharp pokey tools & some colourful language to remove. The single loop of mesh held in place by it’s own spring pressure is much easier to remove as it collapses easily.
I’ve decided to change the mesh size of the screen while I’m in here, in this case to 80 mesh, which is much closer to the OEM screen size. There doesn’t seem to be much of a difference so far in either the starting or running capability of the heater, although the thicker wire of this screen might last longer before disintegrating at the burner end.
nb Tanya Louise Heating Upgrades – Matrix Install
Here the pipework feeding the matrix of the blower unit has been tapped into the heating circuit, the first radiator on the loop is just out of shot to the right, this is all tucked away under the bed in one of the cabins. The pipestat is attached to the flow from the boiler, this will switch on the blower once hot water starts flowing through the system. Isolation valves have been fitted to make the inevitable maintenance of the matrix unit easier, as the system is pressurised to 14PSI, dropping the pressure out of the system without making quite a mess is difficult.
The heater itself is mounted on the other side of a wooden partition in the small space left under a shelf. This made installing the unit like trying to plumb in a radiator through a letterbox ;). 4 60mm ducts snake off to the vents mounted in the wall.
The hot water hoses appear through a hole in the timber to connect to the matrix unit, with some 15mm pipe in between as reducers from the 3/4″ hose to the 1/2″ attached to the matrix itself. The blower is wired in low speed mode only, as running it any faster makes far too much noise from the vents.
As a heating solution, this unit works well onboard. Within a 10 minutes of the diesel heater firing up, the blower automatically comes on thanks to the thermostat, and blows plenty of hot air into the saloon to keep the cold at bay.
eBay Special – LED Disco Light With Built In MP3 Player
Here’s an eBay oddity – it’s got the same light & lens mechanism as the cheap “disco light” style bulbs on eBay, but this one is battery powered & has a built in MP3 player.
This device simply oozes cheapness. The large 4″ plastic dome lens sits on the top above the cheap plastic moulding as a base, which also contains the MP3 player speaker.
There are few controls on this player, the volume buttons are combined with the skip track buttons, a long press operates the volume control, while a short press skips the tracks. Several options for getting this thing to play music are provided:
- Bluetooth – Allows connection from any device for bluetooth audio
- USB – Plugging in a USB flash drive with MP3 files
- SD Card – Very similar to the USB flash drive option, just a FAT32 formatted card with MP3 files
- Aux – There’s no 3.5mm jack on this unit for an audio input, instead a “special” USB cable is supplied that is both used to charge the built in battery & feed an audio signal. This is possible since the data lines on the port aren’t used. But it’s certainly out of the ordinary.
The top comes off with the removal of a single screw in the centre of the lens. The shaft in the centre that holds the lens is attached to a small gear motor under the LED PCB. There’s 6 LEDs on the board, to form an RGB array. Surprisingly for a very small battery powered unit these are bright to the point of being utterly offensive.
Here’s the mainboard removed from the plastic base. There’s not much to this device, even with all the options it has. The power switch is on the left, followed by the Mini-B USB charging port & aux audio input. The USB A port for a flash drive is next, finishing with the µSD slot. I’m not sure what the red wire is for on the left, it connects to one of the pins on the USB port & then goes nowhere.
The audio amplifier is a YX8002D, I couldn’t find a datasheet for this, but it’s probably Class D.
Finally there’s the main IC, which is an AC1542D88038. I’ve not been able to find any data on this part either, it’s either a dedicated MP3 player with Bluetooth radio built in, or an MCU of some kind.The RF antenna for the Bluetooth mode is at the top of the board.
Just behind the power switch is a SOT23-6 component, which should be the charger for the built in Lithium Ion cell.
The cell itself is a prismatic type rated in the instructions at 600mAh, however my 1C discharge test gave a reading of 820mAh, which is unusual for anything Li-Ion based that comes from eBay 😉
There is cell protection provided, it’s under the black tape on the end, nothing special here.
The main issue so far with this little player is the utterly abysmal battery life – at full volume playing MP3s from a SD card, the unit’s current draw is 600mA, with the seizure & blindness-inducing LEDs added on top, the draw goes up to about 1200mA. The built in charger is also not able to keep up with running the player while charging. This in all only gives a battery life of about 20 minutes, which really limits the usability of the player.
nb Tanya Louise Heating Upgrades – Saloon Heating
With the installation of the new diesel fired heater we’ve noticed a small problem – since the only heat source in the saloon is the stove, even with the diesel heater fired up the temperature doesn’t really change much, as the heat from the radiators in the both the cabins & the head isn’t spreading far enough.
The solution to this problem is obviously an extra radiator in the saloon, however there isn’t the space to fit even a small domestic-style radiator. eBay turned up some heater matrix units designed for kit cars & the like:
These small heater matrix units are nice & compact, so will fit into the back of a storage cupboard next to the saloon. Rated at a max heat output of 3.8kW, just shy of the stove’s rated 4kW output power, this should provide plenty of heating when we’re running the diesel heater rather than the fire.
The blower motor has a resistor network to provide 3 speeds, but this probably won’t be used in this install, water connections are via 15mm copper tails. The current plan is to use a pipe thermostat on the flow from the boiler to switch on the blower when the water temperature reaches about 40°C.
The hot air emerges from the matrix via 4 55mm duct sockets. This gives enough outlets to cover both the saloon & the corridor down to the cabins.
Standard 60mm Eberspacher style vents will be used to point the warmth where it’s needed.
More to come soon with the install!
nb Tanya Louise Heating Upgrades – The Pumps
With some recent upgrades to the boat’s heating system, the hot water circulation pumps we’ve been using are becoming far too small for the job. After the original Johnson Marine circulation pump died of old age (the brushes wore down so far the springs ate the commutator) some time ago, it was replaced with a Pierburg WUP1 circulation pump from a BMW. (As we’re moored next to a BMW garage, these are easily obtainable & much cheaper than the marine pumps).
These are also brushless, where as the standard Johnson ones are brushed PM motors – the result here is a much longer working life, due to fewer moving parts.
The rated flow & pressure on these pumps is pretty pathetic, at 13L/min at 0.1bar head pressure. As the boat’s heating system is plumbed in 15mm pipe instead of 22mm this low pressure doesn’t translate to a decent flow rate. Turns out it’s pretty difficult to shove lots of water through ~110ft of 15mm pipe ;). Oddly enough, the very low flow rate of the system was never a problem for the “high output” back boiler on the stove – I suspect the “high output” specification is a bit optimistic.
This issue was recently made worse with the addition of a Webasto Thermo Top C 5kW diesel-fired water heater, which does have it’s own circulation pump but the system flow rate was still far too low to allow the heater to operate properly. The result was a rapidly cycling heater as it couldn’t dump the generated hot water into the rest of the system fast enough.
The easiest solution to the problem here is a larger pump with a higher head pressure capability. (The more difficult route would be completely re-piping the system in 22mm to lower the flow resistance). Luckily Pierburg produce a few pumps in the range that would fit the job.
Here’s the next size up from the original WUP1 pump, the CWA50. These are rated at a much more sensible 25L/min at 0.6bar head pressure. It’s physically a bit larger, but the connector sizes are the same, which makes the install onto the existing hoses easier. (For those that are interested, the hose connectors used on BMW vehicles for the cooling system components are NormaQuick PS3 type. These snap into place with an O-Ring & are retained by a spring clip).
The CWA50 draws considerably more power than the WUP1 (4.5A vs 1.5A), and are controllable with a PWM signal on the connector, but I haven’t used this feature. The PWM pin is simply tied to the positive supply to keep the pump running at maximum speed.
Once this pump was installed the head pressure immediately increased on the gauge from the 1 bar static pressure to 1.5 bar, indicating the pump is running at about it’s highest efficiency point. The higher water flow has so far kept the Webasto happy, there will be more to come with further improvements!
CWA-50 Pump Teardown
Above is a cutaway drawing of the new pump. These have a drilling through the shaft allows water to pass from the high pressure outlet fitting, through the internals of the pump & returns through the shaft to the inlet. This keeps the bearings cool & lubricated. The control & power drive circuitry for the 3-phase brushless motor is attached to the back & uses the water flowing through the rotor chamber as a heatsink. Overall these are very well made pumps.
Here’s the impeller of the pump, which is very small considering the amount of power this unit has. The return port for the lubricating water can be seen in the centre of the impeller face.
Inside the back of the pump is the control module. The main microcontroller is hiding under the plastic frame which holds the large power chokes & the main filter electrolytic.
NextCloud Linux Client Build Script
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
Mercury 30A Ham Radio SMPS
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.
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.
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.
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.
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.
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.
Honda GX35 Clone – Are They Any Good?
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.
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).
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.
Here’s the cam on the back of the plastic pulley. A single cam is used for both intake & exhaust valves for space & simplicity.
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. 😉
The starter side is where the oil sump is located on these engines, along with the dipstick.
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!
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.
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.
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.
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.
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.
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.
OpenVPN Server Speed Tweaks
I’ve been running my own VPN so I can access my home-based servers from anywhere with an internet connection (not to mention, in this day & age of Government snooping – personal privacy & increased security).
I’m on a pretty quick connection from Virgin Media here in the UK, currently the fastest they offer:
To do these tests, I used the closest test server to my VPN host machine, in this case Paris. This keeps the variables to a minimum. Testing without the VPN connection gave me this:
I did expect a lower general speed to a server further away, this will have much to do with my ISP’s traffic management, network congestion, etc. So I now have a baseline to test my VPN throughput against.
The problem I’ve noticed with OpenVPN stock configs are that the connections are painfully slow – running over UDP on the usual port of 1194 the throughput was pretty pathetic:
I did some reading on the subject, the first possible solution being to change the send/receive buffers so they’re set to a specific value, rather than letting the system handle them. I also added options to get the server to push these values to the clients, this saving me the trouble of having to reissue all the client configurations.
sndbuf 393216 rcvbuf 393216 push "sndbuf 393216" push "rcvbuf 393216"
Unfortunately just this option didn’t work as well as I’d like, downstream speeds jumped to 25Mb/s. In the stock config, the tunnel MTU & MSSFIX settings aren’t bothered with, some adjustment to set the tunnel MTU to lower than the host link MTU (in my case the standard 1500) prevents packet fragmentation, MSSFIX let’s the client TCP sessions know to limit the packet sizes it sends so that after OpenVPN has done the encryption & encapsulation, the packets do not exceed the set size. This also helps prevent packet fragmentation.
tun-mtu 1400 mssfix 1360
After adjusting these settings, the download throughput over the VPN link has shot up to 136Mb/s. Upload throughput hasn’t changed as this is limited by my connection to Virgin Media. Some more tweaking is no doubt possible to increase speeds even further, but this is fine for me at the moment.
Ferguson A10RWH Portable Colour TV Teardown
Here’s the other TV that was picked up from the local water point having been put of to be recycled. This one is much newer than the Thorn TV, a 10″ colour version from Ferguson.
The colour CRT used is an RCA branded one, 27GDC85X.
Like the other TV, this one is dual voltage input, mains 240v & 12v battery. This TV is a factory conversion of a standard 240v AC chassis though.
The 12v power first goes into this board, which looked suspiciously like an inverter. Measuring on the output pins confirmed I was right, this addon board generates a 330v DC supply under a load, but it’s not regulated at all, under no load the output voltage shoots up to nearly 600v!
I’ve not seen one of these labels on a TV for many years, when back in the very old TV sets the steel chassis would be used to supply power to parts of the circuitry, to save on copper. Although it doesn’t have a metal chassis to actually become live, so I’m not sure why it’s here.
The main PCB is much more integrated in this newer TV, from the mid 90’s, everything is pretty much taken care of by silicon by this point.
This Toshiba µC takes care of channel switching & displaying information on the CRT. The tuner in this TV is electronically controlled.
The video signal is handled by this Mitsubishi IC, which is a PAL Signal Processor, this does Video IF, Audio IF, Chroma, & generates the deflection oscillators & waveforms to drive the yoke.
There are some adjustments on the CRT neck board for RGB drive levels & cutoff levels. This board also had the final video amplifiers onboard, which drive the CRT cathodes.
Thorn Ultra 6816 B&W CRT TV Teardown
The other day at the local canal-side waterpoint, this TV was dumped for recycling, along with another later model Colour TV. This is a 1970’s Black & White mains/battery portable made by Thorn. It’s based on a common British Radio Corporation 1590 chassis. Having received a soaking from rain, I didn’t expect this one to work very well.
Being so old, there is no electronic control of the tuner in this TV, and only has the capability to mechanically store 4 different channels. The tuner itself is a cast box with a plastic cover.
The mechanical buttons on the front of the TV push on this steel bar, by different amounts depending on the channel setting. This bar is connected to the tuning capacitor inside the tuner.
Unclipping the plastic cover, with it’s lining of aluminium foil for shielding reveals the innards of the tuner module.
Here’s the tuner front end RF transistor, which has it’s can soldered into the frame, this is an AF239 germanium UHF transistor, rated at up to 900MHz.
As the signal propagates through the compartments of the tuner, another transistor does the oscillator / IF mixing, an AF139 germanium, rated to 860MHz.
As the buttons on the front of the set are pushed, moving the lever on the outside, the tuning capacitor plates intermesh, changing the frequency that is filtered through the tuner. The outer blades of the moving plates are slotted to allow for fine tuning of the capacitance, and therefore transmitted frequency by bending them slightly.
Being a dual supply TV that can operate on either 12v battery power or mains, this one has a large centre tapped mains transformer that generates the low voltage when on AC power. Full wave rectification is on the main PCB. The fuse of this transformer has clearly been blown in the past, as it’s been wound with a fine fuse wire around the outside to repair, instead of just replacing the fuse itself.
The back of the set has all the picture controls on the bottom edge, with the power input & antenna connections on the left just out of shot. The CRT in this model is an A31-120W 12″ tube, with a really wide deflection angle of 110°, which allows the TV to be smaller.
The bottom of the mainboard has all the silkscreen markings for the components above which certainly makes servicing easier 😉 This board’s copper tracks would have been laid out with tape, obviously before the era of PCB design software.
The components on this board are laid out everywhere, not just in square grids. The resistors used are the carbon composition type, and at ~46 years old, they’re starting to drift a bit. After measuring a 10K resistor at 10.7K, all of these would need replacing I have no doubt. Incedentally, this TV could be converted to take a video input without the tuner, by lifting the ferrite beaded end of L9 & injecting a signal there.
The flyback (Line Output Transformer) is of the old AC type, with the rectifier stack on top in the blue tube, as opposed to more modern versions that have everything potted into the same casing. The primary windings are on the other leg of the ferrite core, making these transformers much more easily repairable. This transformer generates the 12kV required for the CRT final anode, along with a few other voltages used in the TV, for focussing, etc.
The main EHT rectifier stack looks like a huge fuse, inside the ceramic tube will be a stack of silicon diodes in series, to withstand the high voltage present.
This is the main switching transistor that drives the flyback, the HOT. This is an AU113, another germanium type, rated at 250v 4A. The large diode next to the transistor is the damper.
I’ve managed to find all the service information for this set online, link below!
[download id=”5616″]
More to come if I manage to get this TV working!
Panasonic NV-M5 CRT Viewfinder Hack
The old Panasonic NV-M5 has the standard for the time CRT based viewfinder assembly, which will happily take a composite video signal from an external source.
This viewfinder has many more connections than I would have expected, as it has an input for the iris signal, which places a movable marker on the edge of the display. This unit also has a pair of outputs for the vertical & horizontal deflection signals, I imagine for sync, but I’ve never seen these signals as an output on a viewfinder before.
Luckily I managed to get a service manual for the camera with a full schematic.
This unit takes a 5v input, as opposed to the 8-12v inputs on previous cameras, so watch out for this! There’s also no reverse polarity protection either.
Making the iris marker vanish from the screen is easy, just put a solder bridge between pins 15 & 16 of the drive IC. The important pins on the interface connector are as follows:
Pin 3: GND
Pin 4: Video Input
Pin 5: Video GND
Pins 6: +5v Supply
Behringer DEQ2496 Mastering Processor
I was recently given this unit, along with another Behringer sound processor to repair, as the units were both displaying booting problems. This first one is a rather swish Mastering Processor, which has many features I’ll leave to Behringer to explain 😉
All the inputs are on the back of this 19″ rackmount bit of kit, nothing much on this PCB other than the connectors & a couple of switching relays.
All the magic is done on the main processor PCB, which is host to 3 Analog Devices DSP processors:
ADSP-BF531 BlackFin DSP. This one is probably handling most of the audio processing, as it’s the most powerful DSP onboard at 600Mhz. There’s a ROM on board above this for the firmware & a single RAM chip. On the right are a pair of ADSP-21065 DSP processors at a lower clock rate of 66MHz. To the left is some glue logic to interface the user controls & dot-matrix LCD.
The PSU in this unit is a pretty standard looking SMPS, with some extra noise filtering & shielding. The main transformer is underneath the mu-metal shield in the centre of the board.
Mercedes Benz Temic Central Locking / Immobilizer Module Teardown
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.
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).
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.
Tenma DMM Drivers & PC Software
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:
[download id=”5614″]
Tenma 72-1015
Tenma 72-1016
Tenma 72-1020
Tenma 72-2610
Tenma 72-2620
Tenma 72-7712
Tenma 72-7715
Tenma 72-7730
Tenma 72-7730A
Tenma 72-7732
Tenma 72-7732A
Tenma 72-7735
Tenma 72-7745
Tenma 72-7750
Tenma 72-7755
Tenma 72-7760
Tenma 72-7790
Tenma 72-8400
Tenma 72-8720
Tenma 72-9280
Tenma 72-9380
Tenma 72-9380A
Tenma 72-9405
Tenma 72-9490
Tenma 72-10405
Tenma 72-10410
Tenma 72-10415
Tenma 72-10440
Tenma 72-10445
Tenma 72-10465
IR Remote Control Repeater
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.
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.
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.
Project Volantis – Storage Server Rebuild
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.
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.
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.
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.
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.
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.
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.
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.
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.
Zhiyu ZBP30A1 Electronic Dummy Load
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.
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.
The main heatsink is fan cooled, the speed is PWM controlled via the microcontroller depending on the temperature.
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.
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.
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.
The rotary encoder is used to select the option. Function 2 is battery capacity test mode.
After the mode is selected, an option appears to either turn the beeper on or off.
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.
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. | |||
| otP | Overtemperature Protection | |||
| Ert | Temperature Sensor Failure / Temperature Too Low | |||
| ouP | Power Supply Overvoltage Protection | |||
| oPP | Load Power Protection |
LG Flatron 22EA53VQ-P Power Issue
I was recently given a pretty nice LED backlit 1080p LG monitor, with the instruction that it wouldn’t power on correctly. The monitor would power on as far as the standby light, but when fully powered on, would flash the backlight momentarily then shut down. A power supply issue was immediately suspected.
I popped the covers off the monitor itself first, thinking that it was an electrolytic gone bad in the backlight DC-DC converter. Not to mention the fact that cracking into a wall-wart type of PSU is only occasionally possible without the use of anger & large hammers. (Cracking the glue with the handle of a screwdriver doesn’t work so well when the factory went a bit nuts with the glue/ultrasonic welder). As can be seen in the photo, there’s not much inside these monitors, the logic is a single-chip solution, the rest of the PCB is dedicated to supplying the power rails for the various circuits. On the left is the power input & the DC-DC converter for the backlight, along with the DC-DC converter supplying the logic circuits. None of the capacitors here are damaged, everything looks good.
I then measured the output of the PSU, which under no load was the correct 19v DC. However applying any load caused the output voltage to drop like a proverbial brick. Applying a full load of 1.3A saw the output voltage drop so severely that the PSU tripped on it’s UVLO.
At 200mA of load the factory PSU is already dropping to 18v, with a 5.3kHz switching frequency appearing.
At higher load the frequency increases to 11.5kHz & the output voltage has dropped to 11.86v!
750mA was as high as I could make the supply go without it tripping itself out – the UVLO circuit trips at 9v. 12.6kHz is now riding on the severely low DC at this point.
The power supply is supposed to be rated at 1.3A at 19v, however with this fault it’s getting nowhere near that. The LG brand is on this PSU but it’s contracted out to Shenzen Honor Electric Co. Ltd.
Here’s the problem with this PSU. The output electrolytic has ballooned. I don’t have an ESR tester, but this cap has gone way past it’s sell-by date. It’s position right next to the heatsink with the output rectifier diodes has probably cooked it. The PSU isn’t that badly built for a Chinese one – there’s plenty of creepage distance on the PCB & even a couple of isolation slots.
eSynic 2-Way HDMI Signal Splitter
Time for another random teardown, a signal splitter for HDMI. These units are available very cheap these days on eBay. This one splits the incoming signal into two to drive more than one display from the same signal source.
The stamped alloy casing comes apart easily with the removal of a few screws. The PCB inside is rather densely packed with components.
The main IC on the incoming signal is a Silicon Image Sil9187B HDMI Port Processor, with a single input & 4 outputs. In this case the chip is used as a repeater to amplify the incoming signal. the signal path then gets fed into a Pericom PI3HDMI412 HDMI Demux, which then splits the signal into two for the output ports.
The main pair of ICs processing the video signals are controlled over I²C, with this STM32 microcontroller. The 4 pads to the lower left are for the STLink programmer. The main 3.3v power rail is provided by the LM1117 linear regulator on the right.
