Here’s a DMD Android-based projector from China. This has quite good resolution at 720p native, although the install of Android present is very outdated, and the internal battery has a very short life due to the power draw of the unit.
The top of the main PCB is above, and this has one half of the DMD chipset, and the SoC, Flash & RAM for the Android part of the projector.
Touchpad
The top of the unit has touch buttons and mousepad for operation, in addition to an IR remote, the bottom of the lid moulding has the touch controller for those buttons and pad.
Mainboard
Removing the mainboard shows the rest of the chipset. The large IC at bottom left is one half of the DMD control chipset, and the large IC above that is a video switch to enable either the built in Android or external HDMI interfaces. The rest of the components here are power supply and general support.
Projector Module
Under the mainboard is the projector module itself. Mostly heatsink just to cope with the high power LEDs, there’s a fan in the rear section that keeps everything cool.
DMD Heatsink
The DMD module is definitely from a development kit – it’s hidden behind this small heatsink. The wheel in the foreground is for main focus.
LED Module
On the front of the unit, behind the copper plate is the main RGB LED module, which is switched by the DMD chipset for full colour output from the main lens to the left.
Here’s something that in my primary job as an EMC Test Engineer gets a lot of use – a laboratory grade amplifier for performing the Immunity testing phase of an EMC suite. I figured it was about time to crack them open & have a look at what makes them tick. I’ll start with the 100kHz-1GHz model in this post.
Main PSU
The main PSU providing power to the amplifier & control components is a 150W Meanwell unit in this example. While Meanwell have some fairly decent supplies, they are overall very hit & miss on reliability & especially in the compliance domain – the RSP-1000 & RSP2400 versions claim to be EMC Class B Conducted compliant, and definitely are not! They also claim Radiated Immunity to Industrial levels, but I’ve seen them fail this test, by reducing their output voltage by a factor of 10!
Cooling Fan
A 120mm 12V fan on the rear panel draws cooling air over the internal components. These amplifiers are Class A, so they do generate quite some heat due to the inefficiencies of this operational mode.
RF Amplifier Module
All the wideband RF magic is contained in this module. What’s unusual about these lab amps is the number of decades of operation – RF amplifiers are usually rather narrowband, and it’s very difficult to construct a wideband amplifier that has even close to a flat frequency response. There aren’t many connections; just the RF I/O connectors on SMAs, a ground, main power supply & finally an Enable input.
Control PCB
There’s a small PCB inside to do the safety interlocks, which are BNC connections on the back, as well as temperature monitoring & overtemperature shutdown. This just has a small PIC microcontroller & a few passives.
Main Amplifier PCB
After taking the top off the amplifier module, a small PCB is all that’s in there, with single-sided construction. By the look the rear copper layer is all ground plane. Power supply & enable inputs are dealt with at the top of the board, with the pre-amp stage at bottom right, and finally the main PA stage bottom centre. This appears to be a push-pull design, with dual MOSFETs at all RF stages, and splitters/combiners at the I/O respectively.
It’s time for another CRT-based post! This time it’s a Matsushita 40CB4-based viewfinder from 1980. These came from JVC colour tube cameras, and are physically massive! I’ve already worked out the pinout on the multicore cable here & attached a usable connector.
Information Label
There’s lots of information on the bottom label of this unit, including a notification in German that the X-Ray emission from the device is shielded, and the maximum CRT acceleration voltage is 8kV. This last point is a bit strange, since the 40CB4 datasheet states a maximum design voltage on the final anode of 6kV. I did measure the voltage at the anode cup, and it’s stable at 7.15kV!
Internal Overview
Popping a couple of screws out & removing the enormous eye cup allows the top cover to come off. This unit is very tightly packed inside, with 3 PCBs! The magnifying lens (~45mm diameter) & mirror on the left enlarge & turn the image so the camera operator can see it. The CRT’s at the top, with a copper grounding band around the face.
CRT Face
The CRT face is neatly slotted into the plastic housing, with the tally LEDs to the right of it. The legends on the LEDs are naturally printed in reverse, since they’re intended for viewing through the mirror. The optical section is entirely spray painted black for better contrast & stray light control.
Electronics Area
The other 5″ of the casing is packed with electronics to support the CRT. The bottom PCB even “wraps around” to the right, with copper staples connecting the boards together. The CRT tube itself is hiding inside the deflection yoke and under a foam pad at the top of the unit. It’s secured in place with a copper grounding strap wrapped around the face of the tube, and a spring. A single screw secures the strap to the case. This also provides a local earth for the outer Aquadag coating on the tube, which is the negative plate of the final anode smoothing capacitor. The other plate is formed by the coating on the inside of the CRT glass, and the dielectric is of course the glass itself.
The main anode wire snakes off from the flyback at bottom left to the anode cup at the top of the CRT, insulating the 7kV from everything else.
There aren’t many reasons to jack up the final anode voltage on a CRT, past the design voltage of the tube as JVC have done here. The only plausible one I could think of is to increase brightness of the image, but the Sony 4CB4-based units I have only run at around 3kV, and those are plenty bright enough! The downside here of course, is that with higher energy electrons and a brighter image, the phosphor of the CRT will wear out faster.
Increasing voltage also increases X-Ray emission, but even at the 8kV maximum, such X-Rays would be so weak as to not make it through the CRT faceplate glass, which is loaded with lead anyway.
There’s not much sense in yanking the tube out of this unit, it’s identical to the Sony one’s I’ve done in the past:
Bare 40CB4 CRTVoltage Regulator Pass Transistor
Slotted into a gap above the CRT is a large TO-220 2SD476 NPN transistor, this is part of the power circuit; it’s the series pass element regulating the input 12v down to 9v for all the remaining circuits. The aluminium sheet on the back provides some heatsinking as this part gets warm! Current draw of this unit with no video input is about 260mA.
CRT Removed & Vertical Board
Popping the CRT out allows a view of the Vertical & Power Board. This hosts the input linear voltage regulator, and the vertical output control circuitry. Hiding at the back on the right is a NEC µPC1031H2 Vertical Deflection Controller.
Horizontal & Video Boards
Separating the boards reveals the other two PCBs, the Video & Horizontal/HV boards. The bottom board takes care of the Horizontal output, and the lefthand board the video input, sync separation & amplification.
Horizontal Control IC
The Horizontal section is controlled by a Matsushita AN294 device. Unfortunately I haven’t been able to locate a datasheet for this one. The flyback transformer (Horizontal Output) is on the right, with another smaller transformer I don’t quite know the purpose of. Oddly, there’s no large switching transistor for the horizontal output stage – as the PCB notes the flyback as being a “HVM” this may in fact be more tightly integrated with some of the drive circuitry in the potting. There aren’t anywhere near as many pins on it as a usual CRT flyback has either.
This section also generates the other voltages required by the CRT – 2.8v for the filament, and ~80v & ~400v for the grids.
Video Board
A closeup of the video board shows the relative simplicity. Only 4 transistors are doing all the video actions. There is relatively high voltage on here though – an 85v feed from the power supply which is the rail voltage for the video amplifier to the CRT cathode/G1.
Focus & Horizontal Hold Adjustments
There’s a few adjustments available on this unit, here are the Focus & Horizontal Frequency (Hold) pots. Amazingly, even though this unit is about 43 years old at the time of writing, the unit fired straight up when I applied power & a composite video signal, with no adjustments required at all!
Unfortunately there’s no service manual or schematics that I could find on the web for this or the camera it came from, but connections to make this unit work are very simple:
Wire Colour
Signal Name
YELLOW
+12V DC
BLACK
GND
Coax - Core
Composite Video 1v p-p
Coax - Shield
Composite Video GND
There’s another blogger who’s done this particular viewfinder, but they didn’t dig into the unit anywhere near as far as I usually do:
Here’s a very cheap audio amplifier, from the usual suspects in Shenzhen. This is a Herdio AMP-BTX01 Bluetooth Audio Amplifier. This is a stereo unit, but the quality is going to be piss poor!
Main PCB
Cracking the casing, which is just clipped together reveals the sparsely populated PCB. There’s a 12v power input on the right, along with a line-level input. The speaker outputs are on the left. Between the two are only a few components to do the audio signal processing.
Bluetooth Radio
There’s just the Bluetooth radio IC, an AC21BP0A931. Not much is available on this IC, I certainly can’t find a datasheet, but it has all the low-level audio stuff, a microcontroller & a 2.4GHz Bluetooth radio integrated into a single IC. There’s a 5v linear regulator hiding behind the electrolytic caps to provide a power rail for this. The only other components here are a ruck of SMD ceramic coupling capacitors in the audio lines to the amplifier ICs.
Amplifier ICs
The final components are these Chinese FET audio amplifier ICs, rated at 15W per channel, and driving a speak each in Bridge mode – these are stereo amps.
I’ve been doing quite a bit with eBikes of late, given the current fuel costs in the UK, so the bike I managed to get from work needed a couple of upgrades. Above is one of the best controllers I’ve found, an S830 model. This is very full featured, with Speedometer, Odometer, Trip counter, programmable assist power levels & battery monitoring.
Rear
There’s not much on the rear panel of the device, I’m not even sure who actually manufactures these! There’s a USB port on the bottom for charging a mobile phone etc while riding. The cables are potted into the back of the casing for water protection.
Main PCB
Removing the 4 screws from around the perimeter of the rear panel allows the front to come off with some peeling – there’s silicone & a gasket to keep water out! The module is driven by a Nuvoton N76E003AT20 8051-based Flash microcontroller. Most of the PCB is actually taken up by the DC-DC voltage regulation to be able to handle a very wide input voltage of from around 24V – 84V depending on what battery pack the eBike has, since these are run direct from the battery. The LCD only has a few connections, so it’s probably SPI or I²C controlled.
Harness Connections
All the connections into the harness are marked on the board, which might be handy should the cable need replacing. There are also a few that aren’t used at all, but all the components to support them are populated on the PCB.
Rear Panel
The rear panel has the sealed-in cables, and the USB port module, which is also completely potted. It’s likely there’s another DC-DC under that potting, given there’s clearly a PCB there.
Here’s another module from the decommissioned impulse testing rig – the pulse forming network for the Surge generator section. Lots of high-energy high-voltage parts should be hiding in here.
Resistor Side
Pulling the cover off shows there’s not a lot to the network, but it’s a collection of rather exotic parts. The row of 4 devices on the back panel are Mercury Displacement Relays – these don’t have solid contacts as such, but a pool of metallic Mercury that gets pushed up by a magnetic plunger into contact with both terminals. I’ll do a separate post on these not very common parts. A couple of small chokes wound on large nylon studding are in the centre, along with an adjustable wirewound resistor. On the right is the main energy storage capacitor, rated at 10kV – this thing is enormous, and about half the size of a house brick. The large vitreous wirewound resistor next to it is the safety discharge resistor, switched by the normally closed Mercury relay on the far right. Charging & impulse discharging are handled by the other three relays.
Relay Side
Another view shows a very large stack of high voltage pulse rated resistor pucks, there are three in this stack, held together by a large bolt down the centre.
Time for another Chinese gadget! This time it’s a tiny GPS tracker, designed to look like a standard vehicle relay, the MV730.
Only a partial teardown on this one, since I need the thing to work afterwards, and the unit is very tightly integrated. Not only does this unit look like a relay, it’s exactly the same size. Some serious compaction of the electronics has been done here to get things into such a small package.
GSM Module
On one side is the PCB with the GSM module (it’s on the other side of the board), and the SIM socket. There are also a pair of LEDs to show both GPS & GSM status. The module on this has both GPS & GSM functions, so the active antenna is connected directly to the PCB here.
There is a very small-pitch 4 pin connector just under the antenna connection, I would assume this is for a TTL serial connection to the radio module.
GPS Antenna
The GPS antenna is attached to the top of the assembly by a sticky pad, which has here been peeled off. The other vertical PCB is visible here also, which contains the power supply for the tracker. As this unit can handle anything from 9-90V (allegedly), there’s going to be some DC-DC action on that board. The serial number is also on this PCB, redacted for privacy 😉
Module Top
even the centre of the unit is packed with parts. There’s a plastic frame for general support, and this also has the foil GSM antenna stuck to it. There’s also an 80mAh backup Lithium Ion cell, and an actual relay hiding in the middle which is for the “Fuel Cut” feature of this tracker.
Another quick teardown post! This is a high voltage supply module from Hunting HiVolt – a company that hasn’t been around in some time. This is adjustable, and takes a standard 230v AC mains input to output a +1kV rail & a -250V rail.
Label End
There is a rating plate with some identifying marks, but I’ve not been able to find any information on these units anywhere.
HV Outputs
The other end of the unit has the mains input, and the HV outputs on binding posts, along with an Earth connection.
Cover Removed
A couple of screws allows the cover to come off, revealing the electronics inside. The mains is led straight to a transformer, that outputs 24V to run the DC-DC converter.
High Voltage Transformer
The main HV transformer is on the left, and the switching transistors on the right, attached to a heatsink.
Transformer Windings
These transformer windings are always pretty, no doubt done by machine & varnished for mechanical support & extra insulation.
Control IC
Control is done at the other side of the PCB, underneath the output PCB. Just a standard PWM controller.
Voltage Multiplier Section
The output voltage from the transformer is rectified & smoothed with capacitors, and there is also a voltage doubler hiding under here – this helps reduce the amount of insulation required on the transformer windings, since they only need to handle half the output voltage.
Time for another Rubidium Standard Teardown! This one was supposed to happen a year ago, however I completely forgot about this unit. This is an Efratom / Datum LPRO-101 Rb standard, which does differ somewhat internally from the previous unit I tore down. Above is the unit with the Mu-Metal top cover unclipped. The PCB is very tightly packed with components, and this unit dates to approx 1999. The way all of these units operate is with a standard Quartz oscillator, and locking that to a Rubidium physics package to gain the stability of an atomic reference.
Servo Section
The bottom left corner of the board has the C-Field control & servo section, with the C-Field (Frequency Adjust) pot on the left, with the selectable tuning resistor. There’s a mountain of 74 series glue logic in this unit, and will be visible in every shot. The adjustment pot can be accessed through a tube in the top cover with an adjustment tool.
VCXO Section
Bottom right is the 20MHz VCXO section, with the main crystal in the TO-3 can wrapped in a heatsink at the bottom right. Again there’s more space for selectable components here, with a blank spot for another ceramic cap – most likely to further tune the operating frequency. One of the main regulators is here as well, an LM7805 in the TO-220 package.
Synthesizer Section
Here’s the RF synthesizer, used to indirectly generate the 6.8GHz hyperfine transistion frequency of Rubidium. The synth here frequency multiplies the 20MHz main clock to 60MHz, and feeds this through a coaxial cable into a Step Recovery Diode, mounted inside the microwave cavity with the Rb cell. This section also sweeps the frequency to be able to obtain physics lock when powered up.
Physics Package
This is the very important section of the oscillator – the Rubidium Physics package. This section is heated to high temperature – 100°C for the lamp (the small section on the left), and 70°C for the vapour cell & microwave cavity (the larger section on the right).
Rubidium Lamphouse
The Rb spectral source is hiding inside this small casting, with a barrel tuning capacitor on the side. In these units, the lamps are driven with RF, through a coil of wire wrapped around the glass bulb of the lamp itself. In my case, I managed to pick up a 156MHz signal in this area with a spectrum analyser, so I can only assume this is the drive frequency for the lamp. The main RF drive MOSFET, an MRF160 sits underneath the lamp housing. The driver is a Colpitts oscillator, and drives the lamp with about 4W of RF power. The lamp is heated with a MOSFET thermally bonded to the other side of the housing, which can’t be seen here.
Microwave Cavity
The other end of the physics package has the Rubidium Vapour cell, photodetector & step recovery diode housed in a microwave cavity. The coax cable feeding the 60MHz signal from the synthesizer can be seen going through a passthrough in the brass plate. Inside is the SRD & photodetector. This section is heated by further thermally bonded MOSFETs on the sides of the cavity housing.
Rubidium Lamp Bulb
Loosening the locknut on the lamp housing, and gently unscrewing the gold-plated holder allows removal of the bulb. The tiny bead of Rubidium metal can be just seen in the pinch of the bulb, with a couple of spots on the outer part of the bulb. The lamp voltage on this unit was around 6.21v, however after removing the lamp & giving it a clean, and warming it to get the Rubidium to re-condense in the pinch got the voltage up to 7v – this is plenty healthy for one of these.
There’s definitely some wear though – there’s a slightly yellow tinge to the glass, and from what I have read in a couple of scientific papers on the subject of Rb Lamp Failure Modes, this is probably Rubidium Oxide, caused by an interaction between the metal & the glass.
rubidiumRubidium GlowA final photo shows the very pretty colour of these lamps – it’s a pastel purple colour, and surprisingly the camera picks this up very well.
Here we have an optical power meter, vintage 1991! This is a Gentec unit, with scaling to to handle up to 10W with a suitable powerhead. Powered either with 4 PP3 9v batteries, or from a 24v DC jack on the rear, this unit is quite versatile. I managed to get this for very little money on eBay – similar units cost over £1,500 new – without a powerhead.
Meter Movement
The unit is completely analogue, with no digital circuitry at all. The meter movement has a mirror on the scale for parallax correction. Under the movement are the main power switch & battery test switch, which uses the meter itself to show battery level.
User Controls
The right hand side of the unit has the Zero adjustment, the range switch, and the DB15 powerhead input connector.
Board Left
Taking the unit apart, with just 4 allen screws on the case reveals the mainboard. There’s very little back here! The active components are just Op-Amps – An OP07 ultralow offset in the bottom left corner is most likely the front-end amplifier, along with a few LF442ACN precision JFET input devices in the same area. The other amplifiers are LT1001 precision devices, with a 10mA output current capability. Most of the passives in this area are also high-stability & high precision parts.
Board Right
The other side of the board handles the meter movement, and the power input section. There is a small daughterboard with another LT1001 Op-Amp on board, along with some passives, and the battery inputs go into here, however I’m not exactly sure what this is doing – there is another connection to the rear panel 1v analogue output BNC jack, so it may be the driver for that section. The 24v input is a single DC rail, however the 4 PP3 battery holders are wired as parallel pairs of batteries back to back, so a split +9v/-9v supply is generated.
Main PCB
An overall view of the board shows the wiring back to the battery holder, 1v analogue output jack & DC input connector.
To run my postmix rig, I needed a carbonator, to turn tap water into soda water. These units are very common in pubs in the UK, and are very simple in construction. The unit is fed water at about 3 bar from the water main & food-grade CO² at about 5 bar from a regulator, and soda water appears at the outlet.
Pump Motor
To raise the incoming water pressure above the pressure in the carbonator tank, the unit contains this rather large vane pump, with a 230v induction motor for mechanical power. There’s a solenoid valve on the inlet to prevent water flow when the pump is off, and the motor is automatically controlled.
Electrical
Above the pump is the electrical wiring & control. This is a simple level control, and reads a conductance probe inserted into top of the carbonator tank, activating the pump when the level in the tank drops below a minimum level, and shutting it down when a max level is reached. There’s also a timeout function, which shuts everything down on lockout if the pump runs longer than a preset time interval as protection in case of such issues as a leak in the system, or dry running without a water feed.
Carbon Vane Pump
Coupled to the front of the motor is a carbon vane pump. This type is very commonly seen in food-grade equipment, such as these units, and commercial coffee machines. The unit has a suction strainer, and a built-in pressure relief valve to stop the pipework exploding or the motor from burning out if there’s a blockage in the outlet line.
Carbonator Tank
The final & main part of the unit is this 115mm diameter stainless steel tank, with fittings at the top. This is pressurised with CO², and water is sprayed into it through an orifice. This spray increases the surface area of the incoming water, making it absorb as much of the gas as possible. There’s a pressure relief valve at the top, just in case the internal pressure reaches dangerous levels.
I bought two of these packs for my new DeWalt combi drill, as the branded packs are very expensive and there’s unlikely to be much of a difference in cells used. I was a little mistaken on this, as you’ll see!
Battery Terminals
The top of the unit has the battery connections, with all the cell balance lines, along with an ID pin, and a TH pin. The TH pin connects a 10K NTC thermistor up to B+.
Battery Label
The bottom of the unit has the rating & warning label. This claims to be a 6Ah pack, but it’s nowhere even close!
Top Cover Removed
Removing 4 Torx screws gives access to the internals. The cells are all fitted into a plastic holder. There’s a small PCB holding the connector pins, and all the cells connect up to this for the balance outputs. There’s a small PCB on the side of the pack that holds the components for the battery meter.
Connector PCB
The back of the connector PCB has some passive components, but not much else. There’s the connections for the NTC at the bottom right of the board. There is an IC on this board, on the other side, but without desoldering all the pins, it’s not possible to see properly as it’s mainly hidden by the connector frame.
Battery Indicator LEDs
Not much on the front of the battery meter board, apart from the 3 bright green LEDs and the tactile switch.
Battery Indicator Components
The other side has a small ST microcontroller, a TL431 shunt reference, and some other passives.
Cell Links
All the cells are linked together with hefty interconnects, as expected for a high current pack. This is laid out as a 5S2P configuration, giving 21V max, 15V flat. Unfortunately I can’t see any markings on the cells – they may be off brand, or pulls from other products.
I figured as I always do with Chinese battery packs that the stated capacity of 6Ah was too good to be true, so I ran my usual cycle tests to see what the real capacity was, and was met with the following results:
Cycle Number
Pack A
Pack B
1
3969mAh
3917mAh
2
3963mAh
3947mAh
3
3961mAh
3956mAh
4
3953mAh
3959mAh
As can be seen from the table, these packs are 4Ah, not 6Ah. 2Ah cells sort of make sense for a pack like this, as the high-current capacity cells tend to be a lower capacity.
Since I got my new DeWalt combi drill, I needed a way to charge the batteries without having to resort to sticking blade terminals into the pack connectors – I didn’t purchase the branded charger, mainly due to cost. I also have a very capable multi-chemistry charger that handles multi-cell lithium packs with no issues, so I saw no need to replicate things. This little gadget was ordered just for it’s main pack connector; I can then use this to make up a charger adaptor cable. What this normally does is allow the use of DeWalt XR battery packs to charge mobile devices via 5v USB outputs, so there’s going to be some kind of DC-DC converter in here. There’s also a “charge level indicator” built in, which doesn’t actually do anything sensible – even on a flat battery pack, showing a single LED on it’s charge indicator shows the full 3 LEDs on this unit.
The remaining feature is a trio of white LEDs to function as a torch, but it’s less than stellar in the brightness department. Given that there’s not much in the way of control inside the battery packs themselves, I reckon this unit could actually overdischarge a pack, causing damage.
Torch LED & Charge Indicator
The top of the unit has a large label with windows in for the various LEDs, and a pad covering the tactile switch to operate the torch function.
Label
The label on the side indicates the unit will operate down to 10.8v, good for the 3S packs, as well as the 18/20V packs.
Pack Connector
Here’s what I was after – the battery pack connector. This has the full compliment of pins for all the balance taps too.
Casing Opened
Removing a label, and a single screw gives access to the internals. There’s not much in here apart from a large PCB, with a few components.
Main PCB
The PCB is pretty sparse. There’s a microcontroller in the top right corner that does the torch LED switching, and the “battery indicator LEDs”. This is completely unmarked, which is very common now for Chinese microcontrollers. The only way I’m identifying this one is via a decap operation on the IC!
The USB ports have MOSFETs in their negative pin paths, probably to switch off the ports if they’re overloaded. The data pins are bridged together on one port, and connected to the DC-DC converter on the other port.
DC-DC Converter
The main DC-DC converter IC is in the bottom right corner of the board, next to the input pins. This is an IP6503S multi-protocol USB charging converter, with a 24W power limit. This explains why the data pins of one of the USB ports is connected back here – it’s doing some communications with the connected device for fast charging. Chinese datasheet below.
New tool time! I figured now I’m a fully ticketed member of the F-Gas community, I’d treat myself to passing the course by buying a decent set of refrigeration gauges. This is the Yellow Jacket P51-870 Titan manifold, a fully digital unit with all the useful functions built in. Basically an electronic module attached on the top of the standard Titan manifold, this unit performs all the regular functions I’d normally need either a calculator for, or other tools. The front of the unit has just a power button, LED & a large resistive touch TFT panel for display.
Rear Panel
The rear panel has the ports for charging the internal battery, which is micro USB – this is also used to download log data to a PC from a system processing run. There are 4 3.5mm jacks for the external temperature probes, and vacuum sensor.
Rear Cover Removed
Removing 4 Torx screws in the back panel allows the clamshell case to come apart, showing the mainboard, and the pressure transducers screwed into the manifold. The aux jacks & the USB charging & data port are supported on small vertical PCBs plugged into the mainboard via 0.1″ headers.
Main PCB Overview
With the pressure transducers unplugged from their looms to the mainboard, the module is free from the manifold section.
Main Microcontroller
The muscle of the operation here is a Freescale (now NXP) Kinetis K2 Series MK22FN512VLH12 ARM microcontroller. With a Cortex-M4 core at 120MHz, there’s a bit of beef here. The LCD & touch overlay is controlled by a Bridgetek FT810Q Embedded Video Engine. The video controller communicates with the microcontroller via SPI, and the LCD via parallel RGB. There’s some SPI Flash memory up on the left, for log data storage, a Winbond W25Q32JV 32Mbit part. Just under that is a pressure sensor, which I’ve been so far unable to pull a part number off. This is required to assist in calibration of the main pressure transducers.
In the top right corner of the board is a 74HC595 shift register, with quite a few discrete transistors & diodes hanging around it. I suspect this is used to switch between two vacuum sensors when both are plugged in – from looking at the waveforms present on the sensor interface, the power does appear to be switched ON/OFF on a single sensor at about 1Hz.
My guess at the moment is that the sensor communications are over I²C, by the 4-wire connection, and the very obvious clock & data line on the connector, but I haven’t yet looked deeply into this.
Main Power Supplies
Next to the battery connector (the battery itself is a single LiPo pouch cell, double-sided taped to the front shell, behind the display), are a selection of DC-DC converters, providing all the required voltage rails. No doubt there’s lithium charging control going on here too.
Bluetooth Module
Wireless connectivity is provided for by a Silicon Labs Blue Gecko BGM111A256V2 Bluetooth 4.2 SoC module. These are also fairly powerful parts, with a full ARM Cortex M4 microcontroller hiding inside, clocked at 40MHz. There are as a result two programming headers on this board, in the top left corner, for both this part & the main microcontroller.
Time for some more RF component teardowns, here’s a very high quality Directional Coupler from HP, I believe this was part of a Vector Network Analyser at some stage. The main body appears to be made of Brass, but the entire unit looks like it’s Gold plated – the shine is far too good to be just Brass! Connections are via SMA connectors.
Label
There isn’t much on the label to explain what the specifications are unfortunately. Nothing that can’t be found out with a quick look on a VNA though.
Cover Removed
After removing the 6 Torx screws securing the top cap of the coupler, the internal components are revealed. There is no RF gasket or seal on the top cover, and relies on flat machining for an RF seal.
Internal Components
The internal construction of this unit is a little different from what I’ve seen before in directional couplers. The arrangement is usually parallel copper tracks on a suitable RF substrate, but in this case, HP have used a very small diameter Coaxial cable, covered with ferrite sleeves on the outer shield. The large square block in the middle is rubber, and may just be to stabilise the assembly. It may also be loaded with ferrite powder to give some RF properties too.
The ferrite cores are secured in place with beads of black silicone, again probably to prevent movement under vibration.
Input End
The input of this coupler is AC coupled via a capacitor, and then fed into the centre core of the Coax. The forward power output pin, visible at the top of the track, is coupled to the centre core of the coax by a tiny carbon track making up a resistor, via another ceramic capacitor. The track is more directly coupled via another carbon trace to the outer shield of the Coax. I believe this coupler is damaged, as the carbon trace that goes via the capacitor has a break in the centre, but the coupler does seemingly still work.
Output End
The other end of the coupler is very similar, although with no main line coupling capacitor, it’s direct fed to the SMA here. The reverse power output is connected the same way as the other, with a network. The carbon trace here though doesn’t have a break.
Here’s some damage to a 1-week old Epever Tracer 4210AN MPPT Charge Controller, where some of the power FETs have decided they’ve had enough of this world. These are Alpha & Omega AON6512 N-Channel Enhancement devices, rated at 30V 150A. From probing around, these seem to be on the battery bus for output protection – they’re just used as power switches in this application. The controller did work in this state, but charging from the solar input was accompanied by a very strong burning PCB smell.
I’m not sure what caused the failure, but as they’re all in parallel, if a single device failed, then it’s likely that the remaining parts having to then compensate for the extra load put them under enough stress to cause a failure.
The hot air gun was used to get the old parts off the board, which had got hot enough to fully oxidise the solder on the thermal pad, along with causing a bit of damage to the PCB itself. I scrubbed the board with a fibreglass pencil to try & get all the Magic Smoke residue off, along with any oxide on the copper. There has been some flaking of the soldermask, but luckily only between connected pads, and not around the gate pads. There was some unfortunate collateral damage to the main fuses, with minor melting of the plastic case, but they’re still electrically intact.
Reflowed Replacements
Replacement MOSFETs were sourced from Farnell, in this case ON Semi NVMFS5C628N parts, rated at 60V 150A. Since these parts are in a DFN package, solder paste & hot air was used to reflow them back onto the cleaned pads, and then everything checked for short circuits.
The replacement FETs have slightly higher RdsOn resistance, but this shouldn’t be an issue.
Now it’s time to dig into the main contactor pack from the hybrid battery I tore down in a previous post. This unit contains the main output relays, precharge components, current measurement & protection. It’s pretty heavy, which isn’t surprising when you realise how much copper there is in this thing! Manufactured by Lear Corporation in the US, this is a seriously heavy duty piece of electrical engineering.
Cover Removed
Once the cover is popped off, the first thing is a large PCB on the top, and some low current wiring. Not much to see yet.
Control PCB & Current Sensor
The main control & current measurement PCB is on the top of the unit, in a plastic frame. This is a complex arrangement in itself. Unfortunately I’ve not been able to identify any of the main components on here, as everything is conformal coated, so the numbers are obscured!
Main Control PCB Top
Removing the assembly from it’s plastic frame reveals a flex-rigid assembly, which is normally folded in half. The main CPU is on the top layer, and most of the power supply & measurement electronics on the bottom. There’s some serious isolation here on the right as well.
Main Control PCB Bottom
The bottom has the connectors, and some power supply components. The main current shunt is on the left, this would be in the negative return side of the main battery bus.
Main Control PCB Reverse
Not much on the backside of the assembly, apart from a few transistors & passives.
Control PCB Removed
Once the control PCB assembly is removed from the main frame, the high current bus bars become visible. There are 3 switching devices in here, two for the main battery bus, and a smaller one for the precharge function. There’s also a main fuse hiding in the middle.
Main Positive Contactor
The main battery positive contactor is tucked in on the left side, with the precharge leads across it’s contacts. This normally isolates the car from the batteries when open.
Precharge Components
Precharging is dealt with by this collection of components. A smaller relay, and a large ceramic 15Ω resistor limit the current that can be drawn when the vehicle is enabled. Closing the main contactors first would potentially cause damage due to the enormous inrush currents caused by the large filter electrolytic capacitors in the traction inverters.
Main Battery Fuse
The main battery fuse, in the DC + line from the cell modules is a 350A rated unit, 450v DC. Being a HRC type, this is capable of breaking 6kA under fault conditions.
Panasonic AEV14012 Contactor
Here’s one of the pair of main contactors, Panasonic AEV14012 400v DC, 120A rated units. These are serious devices, having a hermetically sealed ceramic capsule around the contacts, and a Hydrogen filling!
Main Contacts
Connections are made via big copper slugs, with M4 screws in the ends. There’s a barrier between them to protect against flashover.
Ceramic Capsule
Pulling the top plastic cap off reveals the ceramic capsule containing the contacts. This is the Hydrogen filled space of the contactor. The reason for the hydrogen fill is arc quenching.
Arc Magnets
The contact capsule sits in a permanent magnetic field, provided by these small ceramic magnets. These assist in pulling any arc towards the ceramic walls of the contact capsule, helping to cool & extinguish it.
Here’s something I didn’t think I’d be doing! Here’s a teardown of a BMW 5 Series G30 530E Hybrid Battery pack – a monster 351V, 9.2kWh Lithium pack, obtained for it’s cells to replace the boat’s aging lead acids.
This is something I didn’t have the safety gear to do right of the bat – opening one of these packs is a potentially lethal exercise, with 6 unfused battery modules in series, quite capable of blowing pieces off a nice conductive sack of salt water like a person. Cue the purchase of high-voltage rated gloves for protection, just while I got the pack split into something more manageable.
Needless to say, the combination of current capacity & voltage present in EV or Hybrid vehicle battery packs is nothing short of lethal, and these units should be treated with considerable respect.
Hybrid Battery Pack
Here’s the beast of a battery. Enclosed in an aluminium cast housing, it’s very heavy, and definitely not a one-man lift!
Cover Removed
After removing the top cover, secured by combination Torx/10mm hex bolts, the internals of the pack are visible. There’s no sealant on the cover, just a large rubber gasket, so this came off easily. There are 6 individual modules in this pack, all wired in series with massive links. There’s also a cooling system for each battery module, supplied with refrigerant from the car’s AC system – there’s a TXV mounted on the side of the battery pack. I didn’t see any heaters present, but I don’t know if BMW have done any neat reverse-cycle magic to also heat the modules if required using the AC system on the car.
Left Side Modules
The modules are arranged 3 to a side, double-stacked at the back, then a single module at the front. The pack would normally sit under the rear seats of the vehicle, hence the unusual shape. The refrigerant lines going to the evaporators on this side of the pack can be seen in the bottom right corner.
Output Cables & Contactor Pack
The main contactor pack is on the left side, just behind the massive DC output connector. I’ll dig into this in another post later on.
Right Side Modules
The right side of the pack is arranged much the same as the left, the main difference here being the battery ECU is tucked in at the top here, along with the interface connector to the car, and the refrigerant lines to the TXV on the outside, which I’ve already removed. Each module has a cell balance control unit, in this case one is mounted on the top of a module, and on the side of the module in the lower right corner.
Cooling Evaporator
Once all the modules have been removed, the evaporator matrix is visible on the bottom, a series of very thin aluminium tubes, designed for the best contact with the aluminium frame of the battery modules.
Module Cell Layout
Popping the plastic insulating cover off the battery module reveals the internal construction. I’ve not been able to find exact data on these cells, but I’m assuming them to be a similar chemistry to the ones used in the BMW i3 packs, so 4.15v Max, 3.68v nominal, 2.7v Minimum. The alloy frame itself is of laser welded construction, and there are 16 cells in series per module, giving about 58.8v per module. These will need to be reconfigured as 4 sets of 4 cells in series for 14.72v.
All the individual cell taps are nicely loomed down the middle of the module to each cell, and there are 3 temperature sensors per module (the red epoxy blobs).
Cell Welded Links
The individual cell links are laser welded to the terminals of the cells, so this does make life a little more difficult when it comes to reconfiguring them. The links appear to be made from Aluminium, so soldering is going to be a bit more tricky than usual.
Time for another projector! This one was brought to me with a fault, described as a shadow in the middle of the image, shortly after the lamp was replaced after exploding. This is an older DLP projector, with a UHP mercury lamp. I’ve already removed the top cover of the projector here, showing the internals. The light engine is along the front of the unit, with the lamp on the right. The main control board on top contains all the image processing logic & control functions.
Mainboard
The other side of the mainboard holds the processing chipset. This is probably one of the biggest flip-chip BGA packages I’ve ever seen, the DDP2000. Along with the DAD1000 on the right, these format & send the image data to the DLP chip, via the large white header.
Main PCB Removed
After the mains PCB is removed from the chassis, the rest of the light engine is visible. The DLP is hidden on the left, behind the large heatsink & interface PCB. The light engine is spread out a lot more on this projector, across the entire front of the unit.
Light Engine
A closeup of the light engine shows the back of the phase sensor for the colourwheel, and the mounting brackets for the optics.
Colourwheel
The dichroic colourwheel is tucked into the gap between the lamphouse & the first optic.
PSU Section
Hiding at the back of the projector is the alloy frame holding the power supplies & cooling ducts.
DC PSU & Lamp Ballast
After removing the brackets, the DC power supply & the lamp ballast are visible. Since this projector uses a UHP arc lamp, the DC power supply which has the usual low voltage outputs for the logic board, has an auxiliary output from the +340v rail after the PFC circuit that supplies power to the lamp ballast.
Lamp Ballast Control PCB
The lamp ballast is a pretty standard design, using an Osram control board.
Homogeniser & Lenses
After removing the top cover with the colourwheel, the main optic chain is visible. The usual mirror tunnel homogenizer at the start, with a convex & aspheric lens on the left.
Lamphouse Thermal Cutout
The lamphouse has a last-resort thermal cutout to shut the ballast down if the cooling fans fail. These lamps output some serious heat, and likely wouldn’t last longer than a couple of minutes without cooling.
DLP Optics
The final turning optics before the DLP chip are hidden in the Mg casting of the light engine.
DLP
The DLP is the older type, with the large ceramic LGA package.
Projection Lens
After the DLP, the light is routed through the objective lens, to the screen. This is the back of the lens inside the light engine.
Failed Optic
And here is the main problem with the projector – the last lens in the optical chain before the DLP chip has been roasted by the intense light flux from the lamp. Unfortunately NEC cheaped out on this one – it’s the only optic in the machine that isn’t made of glass. This was likely caused by some contamination on the lens, which starts the process of absorbing light on the surface. The resulting heat then causes discolouring of the lens, which absorbs more heat. A chain reaction ensues, ending in the lens completely destroying itself.
Autofocus
The projection lens has a couple of sensors, for the focus & zoom, along with a focus motor. This is driven by feedback from a distance sensor in the base so no manual focusing is required.
Yet another wonder of Chinese mass-production, this is a cheap (£10 shipped) oil/fuel transfer pump from eBay. Primarily intended for removing oil from engines through the dipstick tube, these are usually sold for all kinds of pumping uses. As will become clear, pumping highly flammable liquids with these might just be a bad plan. Power is supplied through a pair of croc clips, from a 12v battery. Power consumption is quoted at 5A, with a max runtime of 30 minutes.
Power Switch
The coiled cable runs into the back of the plastic housing, where a power switch is also mounted. There’s some ventilation holes, but nowhere for air to flow in at the other end. Smart.
Pump Assembly
Removing the 4 screws on the front cover allows the pump unit to slide out, this is just held in place by the clamped halves of the housing on the rubber grommets on the pump ports. This is definitely a positive-displacement pump, as would be required to be self-priming.
Gear Reduction
The pump is driven through a gear reduction from the motor.
Motor
The motor itself is a bog-standard brushed type – and the reason why flammable liquids such as Petrol should not be pumped with this unit. It’s not ignition protected by any stretch of the imagination, and my guess is the shaft seal isn’t brilliant. So any combustible vapour around the motor is going to be ignited quickly by the sparking brushes on the commutator.
Vane Pump
Removing the front cover reveals the pump’s innards. It’s a sliding vane pump! The vanes themselves are made from copper-plated steel, the rotor looks to be metal injection moulded from iron or steel. As the housing is a soft alloy – probably Zinc or Aluminium – I would predict that the steel vanes will make relatively short work of the housing, rather rapidly wearing away the inner surface. Only time will tell on this one.
Splined Shaft & Seal
The rotor is only slipped onto the shaft splines, and comes out easily. The shaft itself does have a seal.
Another Chinese eBay teardown! This is a “720p” LED projector, available from nearly everywhere for very little cash. But they are very little cash for a reason – they’re total shit. The resolution as stated is a blantant lie – the LCD panel used in these is usually around 320×240, nowhere near the 1280×720 as stated. Being small & portable, there’s very little lighting power available, and they barely work to a level watchable without eye strain even in a completely dark room. You literally get what you pay for! Above is the projector with the top removed, showing the main board, which is fairly densely populated.
Mainboard Top
The main processor appears to be an MST3M182VGC-LF-Z1, a SoC designed specifically for LCD TV applications. This runs the internal firmware from a serial flash, a PN25F32 32Mbit (4MB). As this projector has the capability to play files from USB & SD Card, as well as from A/V inputs, there’s an Alcor Micro AU6438BS USB 2.0 Single LUN Flash controller on the right to deal with the MicroSD slot interfacing. The left top corner of the board is completely dedicated to power control, with various switching converters & transistors.
Mainboard Bottom
The bottom of the board is also dedicated to the remaining portion of power control – more switching regulators here generate the voltage rails required for the SoC, along with LED drive.
Optical Path
Removing the board allows access to the optical components of the projector.
LCD & Lenses
Here the LED module has been removed from the casing, better showing the optical arrangement. There’s a Fresnel lens, then a polariser, the LCD panel itself, another lens, then the final turning mirror to the objective lens.
Turning Mirror & Objective
Here the rest of the optical components have been removed, showing the objective with it’s helical focusing track, which moves the lens, and the turning mirror. Behind the mirror is the pitiful speaker.
Optical Components
Here the main components are laid out, with lenses either side of the LCD & polariser.
LED Module
Now onto the light source of the projector – the LED module. This is buried inside the module with a conical reflector, and a small heatsink on the back.
Reflector Removed
Removing the reflector shows the LED itself, with a thermal fuse in series for protection. The LED is screwed to the aluminium heatsink for cooling – my guess is this is roughly a 6W LED, with 3 series pairs of dies in parallel.
Well, this is what happens when a Variac rated at 3A is subjected to 15A for a while – a complete burnout. The smell associated with this failure was formidable, it’s a shame I can’t convey odour through photos! Above is the burned section of the winding (it was set for around 115v output from our 240v mains).
Top Cover Removed
At first the rotor was stuck in position, but a bit of force allowed some movement. The armature holding the brush has melted at the rivets, and the copper tail from the brush is severely heat-discoloured. This got HOT! When brought to me just after failure, it was near impossible to hold onto the outer casing!
Smoke Residue
Underneath the control knob, there’s white ash, which has evolved from the insulation burning off the windings.
Shorted Turns
A closer look at the point where the brush was set shows the pair of windings have pretty much fused. The worst of the heating occurred here it seems.
Windings
The heating has extended down the windings and the insulation has melted all around the top & base of the toroid core. Unfortunately it’s the end of the line for this particular transformer, and it now rests in the Black Museum of Electrical Death.
These projectors were very popular when they first appeared on the market with the laser hobbyist community, and for very good reason – they contain a massive array of 445nm Royal Blue laser diodes in their optics engine. Originally very expensive, these units can now be had for under £50 on eBay, usually with damaged DLP chips.
Laser Module Door
Under the door on the bottom of the projector is the 445nm Laser diode array module, itself secured in place with security screws to the beam combiner. The rack of 3 high speed fans to the left draws air over the substantial heatsink.
Top Cover Removed
After removing the shell securing screws, the top cover comes off with the button panel. This gives a view of the internals, mostly PCBs at this stage.
Main Control Board
On the left side of the projector is the main control PCB, with the video handling circuitry.
DLP Chipset
At the top of the board is the main DLP image processing chipset, these two components are actually custom parts, so no datasheets are available. The main DLP IC has some DRAM & a Spansion serial flash for firmware storage. There’s also a small audio amplifier on the left to drive the onboard 2W speaker.
System Microcontroller
Further down the board sees an unpopulated BGA footprint, with more space for DRAM. The main system microcontroller is on the right, a Renesas part.
Phosphor Wheel Motor
Right at the bottom edge is the connector running off to the phosphor wheel drive motor.
DC-DC Power Management
The reverse side of the board is pretty sparse, there’s quite a few passives & power control. Down towards the bottom surrounded by inductors is the system power management IC, the DLPA100. This takes the incoming DC 12v rail from the connector on the right side of the board & produces several supply rails for the internal logic: 1.1v 1.8v, 2.5v, 3.3, 5v & also contains the 3-phase brushless driver for the phosphor wheel motor. The main control board input power connector also has a +5v from the mains supply, for standby power. The main board signals the PSU to switch on the main +12v rail through a pin on this connector.
HDMI Interface Chipset
The other end of the board just has the connectors, a bit of glue logic & the HDMI interface chipset.
Main Board Removed
After unplugging all the connectors, the massive cast frame of the light engine is visible.
Phosphor Stripe
Here’s a closeup of the phosphor stripe around the edge of the wheel. This takes the 445nm light from the laser module, and converts it into green. There’s also a frosted glass section of the wheel to pass some blue for the image. The reason for the phosphor being in a large stripe on the wheel is load spreading – there’s several watts of optical power focused down to a very small spot on this phosphor, and would overheat quickly if it wasn’t moving.
DLP Frame
At the back of the light engine is the DLP module, with it’s substantial heatsink.
Light Source PSU Board
Hiding under the mains PSU, is the light source control PCB. This contains several DC-DC converters, which run the 4 strings of laser diodes, the large Phlatlight Red LED & it’s associated TEC cooler. This board takes the incoming +12v from the mains PSU through the multi-way loom at top centre. There are multiple cores on this connector to spread the load – at normal brightness, in Eco mode, I measured the power consumption at about 8.5A at 12v input for the entire projector.
DC-DC Converters
The left side of the board is dedicated to the high power section of the controller. There’s a power inductor for every channel.
Light Source Drive Board
The other side of the board is very heavily populated with components.
Control Logic
The right hand side has the control logic, a Lattice CPLD, and another Renesas Microcontroller. There’s also some glue logic here & a dedicated DA converter.
Power Drivers
The other end of the board has the power drive control logic. There’s a MAX16821AA LED buck driver for the Red LED, and 4 drive ICs for the laser diodes, which are marked <009 LDGC N249. I haven’t been able to find anything about these, so they may be custom.
DLP Light Engine
Removing some screws allows the entire optical assembly to be removed from the lower shell. This may be mostly manufactured from a magnesium alloy from the rather low weight.
DLP Board
On the back of the DLP module is the DLPA200 Micromirror Driver IC. This generates the high voltage bias supplies for the DMD chip (+/-28v) from the 12v rail, generates all the timing waveforms required for the DLP chip. There’s a couple of power inductors for the onboard regulators. Video data is sent from the main image processing chipset to the DMD chip via 2 channels of LVDS.
DLP Mount
Now the heatsink has been removed, the rear of the DLP chip can be seen, with the remains of the thermal pad. The mount for the heatsink is sprung, to accommodate thermal expansion.
Red PhlatLight
The Red light required to create a colour image is generated by a giant LED, more on this one later.
DLP Removed
Here’s the DLP board removed from the projector with the micromirror surface visible. This DLP has many dead pixels, hence the decommission at ~4500 hours of operation.
Laser Beam Combiner
The 24 laser diodes have their beams combined by this knife-edge mirror assembly, turning the beam through 90° to the lens on the left, which focuses the 24 beams down to the optics engine.
445nm Laser Array
Removing the beam combiner from the array allows the 24 diodes to be seen, mounted under their collimating lenses. This is one beast of a laser unit!
Dichroic Optics
Taking the cover off the optics assembly allows the main optical path to be seen. The blue laser comes in a bottom left, through the lens, the red LED comes in bottom right. The pair of dichroic mirrors manage the light path for the red & green light, while passing the blue straight through.
Optical Path
Here’s another view of the optical path, with both light sources visible.
Light Homogenizer
After the light source, is the homogeniser – this tunnel of 4 mirrors facing each other evens out the light beam & removes all coherence from the laser light. This is important to not have any speckle in the image.
Focus & Zoom Motors
Underneath the objective lens are the pair of stepper motors that drive the focus & zoom mechanisms, along with their position sensors.
Turning Mirror
Just after the homogeniser, is the final optical path to the DLP. Here the light comes in a bottom left, and hits the turning mirror, after which it is focused onto the DLP chip by the mirror top centre. The objective lens is through the hole in the centre of the optical block, while the DLP is on the right side.
DLP Final Optics
Here’s where the DLP will be mounted in normal operation, with it’s lens in place.
Objective Lens
Finally, the created image is passed out through the objective lens to the projection screen.
Hall Effect Sensor
There’s a sensor mounted on the side of the lens barrel, that I think is a Hall effect device, but I’m unsure what this would be used for, as there is no magnet anywhere near this to sense. It could also be a temperature sensor though, for the DLP & lens assembly.
Stepper Motor Drive
The small PCB on the side of the lens unit holds the stepper motor drive IC, an LB1937 from Sanyo. There is another IC here, which looks to be a microcontroller.
Lens Assembly
Removing the top cover allows the moving lens assemblies to be seen. These move independently of each other to implement focus & zoom, via lead screw drives on the stepper motors.
Blue Light Path
Here I’m shining a separate 445nm diode laser into the optical assembly, through the blue optical path. The phosphor wheel is turned to the clear section, which allows the 445nm light to pass straight through, being turned 180° by the mirrors & directed out towards where the DLP assembly would be.
Green Light Path
Turning the phosphor into the light path causes a very bright green light to be generated, and passed back towards the 445nm laser entry point. The dichroic mirror in the way reflects this light to the left, through a lens & then to the other dichroic mirror to be turned another 90° to the DLP assembly. I’m not sure where the magenta light is coming from – the phosphor probably generates light on more wavelengths than just pur green, giving some red to mix with the blue.
PhlatLight LED
Here’s the Red LED removed from it’s cooling & collimation assembly – this has an enormous silicon emitter area, and apparently these LEDs are designed to be uniform in light emission, specially made for projection use. There’s a thermistor onboard for temperature sensing – sensible when the datasheet gives CW currents of 8A, and pulsed currents of 13.5A!
LED TEC Cooler
Not surprisingly, cooling this beast of an LED requires more than just a heatsink, so it’s mounted on a TEC module, possibly around 40W thermal capacity.
Fan Control Board
Fan control is handled by this little PCB, squeezed in between the optics engine & 445nm Laser array. There’s a SMSC EMC2305 I²C 5-channel PWM fan controller on here, communicating back to the main system microcontroller. Besides some passives, and 4 transistors to make sure the fans don’t start at full power when the projector is powered on, there’s not much else.
Here’s a recently failed 5W GU10 lamp, which is completely dead – not even a single LED still shining.
Markings
According to the markings, this lamp draws 50mA at 230v & outputs 345 lumens
Lens Removed
After popping the lens off the body, the failure mode is obvious. The top right LED has the Black Spot Of Death, where one of the LED dies has catastrophically failed in service. As these lamps usually have all the multi-die LEDs in series, a single failure will cause the lamp to totally fail. Running LEDs hard, with little cooling is a common cause of this kind of failure. There isn’t much in the way of heatsinking in this lamp, as the outer casing is plastic, and even though the LEDs are soldered to an aluminium cored PCB, the only other heatsink is the aluminium base for the PCB, which is in contact with the outer plastic.
PSU
Removing the LED board & backing plate allows access to the power supply in the rear of the lamp. There’s no switching supply in this one, just a large film capacitor.
Capacitive Dropper
Snipping the pins off the back allows the PCB to be removed, exposing the capacitive dropper from the mains. The output electrolytic cap has also failed on this board, as can be seen from the opened vent on the top.
PCB Reverse
There isn’t much on the back side of the board, apart from the bridge rectifier & a couple of resistors.
This unit recently appeared on eBay, as a spare part from a refrigerant charging machine, and I figured it would make a good explorational post. This unit analyses the purity of R-134a refrigerant gas, using an Infrared sensor cell, and communicates over RS-232.
The sensor cell itself is at the top right of the board, we’ll get to that later on. There’s a small diaphragm pump at the lower right, for purging the cell with air. The port with the red cap is the outlet, and the remaining open hose barb is the input of gas to be tested. This would connect to a flow regulator & solenoid valve that the board controls.
It’s pretty clear that this board has multiple applications from all the unpopulated components. There’s space for a keypad, indicator LEDs & an LCD on board, so maybe this can also be fitted to a handheld analyser?
Power Supply
From looking at the input circuitry, I can surmise that the input voltage is somewhere between 12-24v DC, as there is a 35v input electrolytic filter capacitor. There’s a couple of switching regulators which generate 5v & 3.3v rails for the board, with some input fusing.
Main Connector
There’s two serial links on this board, driven from the main microcontroller – the primary one is on the connector marked JMAIN, along with the power input & a couple of other unknown signals.
MSP430 Microcontroller
Over on the other side of the board is the brains of the operation – an MSP430 microcontroller, with an RS232 transceiver IC & another RS-232 port marked COM2. The remaining connector is a JTAG port for the micro.
Gas Analysis Cell
Here’s the gas analyser cell itself, sandwiched under another board. There’s a temperature sensor on the side of the cell at the bottom, and even though there’s many pins on the header here, only a couple are actually used for the IR emitter.
IR Emitter
Removing the screws from the top allows the board to be removed, which exposes the Mid-IR emitter component with an exposed element. This looks to be very fragile, so I won’t be messing with this much. From metering the connections, this appears to be driven at about 2v from the microcontroller.
Top Of Gas Cell
The window into the gas cell looks to be made of something exotic – considering the IR application & the colour, this is probably Zinc Selenide.
Gas Test Cell
Removing some more screws on the bottom exposes the bottom of the cell with another IR window, and an O-Ring where a pressure sensor sits.
Output Amplifiers
There’s a couple of very accurate LT1884 Rail-To-Rail Precision Op-Amps next to the cell, most likely used to measure the output from the sensor itself.
Mid-IR Sensor & Pressure Sensor
Finally, there is a dual-window thermopile sensor, and a pressure sensor. I wasn’t able to get any information on either of these, but I did find some ranges of sensors for Mid-IR measurement operations, that mentions a wavelength around 10µm for R-134a spectroscopy.
I will try to get this module going & measuring some gases, if I can work out how to talk to it – I already know the serial lines so it’s just working out a command set. If anyone has any information on these, please do get in touch! A service manual for the refrigerant machine this came out of would be good!
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