Motech / Amrel PPS-1002 diagram/schematic

[snoozer]

Hello,

recently I got an Amrel branded programmable power supply model PPS-1002. So far I found out its actually made by Motech in Taiwan. I did find the user manual on the internet alright but no schematic or diagram. The URLs I find for Motech dont seem to work. There was one here in the forum for Motech Europe and also motechind.com from the manual does not work. There is motechsolar.com alright, I have contacted them to check if I can obtain the desired documents without any luck so far. I also contacted Amrel, again, no luck yet. Wondering if anybody here has the schematic or could point me in the right direction. From what I have seen on the Internet so far the different PPS models differ quiet a lot on the internal layout and construction. The PPS-1002 has a what looks to be the Digital PCB at the bottom, another PCB is connected via 2 PCB connectors standing up vertically. That looks to be the analogue board. The toroidal transformer is right behind the front panel and there is a small PCB with the main cap and rectifier just by the AC connector. I try to attach a picture here to the post.

I would appreciate if anybody could help.

Kind Regards
Jan P.

[snoozer]

Hello again,

so what I thought was a broken PSU turned out to be just a calibration issue. The symptoms where the output voltage would be off by about 200mV to 2V between a low and higher voltage setting. Current readings have been off by 1-2A. Checking voltages of the +5V, +15V and -15V rails turned out just fine and nothing looked damaged and nothing got hot or smelled bad. Just to see what happens I just went through the calibration process with my bench DMM and it turns out it must have lost its calibration or was calibrated wrong. Now the PSU works as expected.

If someone does have a schematic/diagram I would still appreciate if I could get that somewhere or download it.

Kind Regards
Jan P.

[snoozer]

Just an update on how this developed so far re schematic etc.... I have received nothing back from Motech as of yet. Amrel tech support was kind enough to at least respond.

Quote:
AMREL’s Power Division was acquired by AMETEK PPD back in 2010

So I have contacted Ametek tech support.

Regards
Jan P.

[snoozer]

So another update. After I was pointed in the direction of Ametek I had emailed them. I got a response soon after with a "Service Manual" BUT unfortunately the schematic of the PCBs did not make it in the PDF. The index has them listed but the pages are not present. However it gives still some valuable information. I try to attach the PDF here.

Also there is an article on Hackaday about one of the PPS series PSU here: https://hackaday.com/2019/12/28/peek-inside-these-same-but-different-power-supplies/

Have a good day.
Jan P.

PS: Waiting for an EPROM programmer, one I have that I try read the firmware from the EPROM and make that available here as well.

[eblc1388]

My unit is MOTECH PPS-1204, its a dual channel 30V2A model.

When I got it in 2016, I tried to understand the operation of the communication between master board and the two channel boards(image below).

Failing to find any schematic, I have drawn up part of the circuit diagram of the DAC unit which is used to set the voltage/current and overvoltage trip point. I have attached a copy and hopes it can give you some insights into the operation of the unit.

[snoozer]

Thank you eblc1388 for sharing your schematic !! The PCBs look very much alike, I seem to have a few more components but the layout at 1st glance is identical. I have a picture of my PCB attached. I assume because I have the remote 0-10V U and I adjustment I might have more populated footprints.

Kind Regards and thanks again!
Jan P.

[eblc1388]

I have noticed that the power transformer in the photo you posted for PPS-1002 also show some slight damage similar to the unit I have, see below:

Please check and provide extra insulation to the transformer as required.

[snoozer]

My transformer is smaller, its only a single channel PSU. The diameter is not enough to reach thye lid. The brackets its mounted to however is a bit bend. I suspect it had a rough landing at some stage. No mechanical damage is visible otherwise. 2 of thye AC wires are trapped under the mounting disk, I will remove the transformer get that sorted and same time bend that bracket back to shape.

Regards
Jan P.

[eblc1388]

All is well then.

I've finally got my Logic Analyser attached to my PPS-1204 Power Supply to visualise the information transfer between Master controller and secondary. The connection points is shown in the following image. With the case cover removed,  I also take the opportunity to make a copy of the microprocessor 80C32 firmware ROM 27C512 and the EEPROM 93C46. However, the GAL16V8 on the master board is soldered and difficult to access without removing all the boards. If this IC failed, the whole power supply will be trashed as its content is probably protected. Reverse engineering the GAL fuse file would require knowing all its pins connection and probing all its inputs and outputs to figure out the combination logic between inputs and outputs. I don't think it will contain any clocked logic so it can be done. Maybe someone had already done that.

Files attached to this post:
1. Firmware of the PS BDY-1204FCE and EEPROM data
2. About 20 images of the logic analyser result under different situations like output voltage and current setup, overvoltage protection setup, mode changes, clocking frequency and data refreshing rate...
3. A text file about the operation of PPS-1204, updated according to the service manual

Here are some of the images.
 

[snoozer]

Wow, thank you eblc1388. Most of it is well over my head but great to have some more information. My EPROM programmer has arrived now so I shall try read the EPROM out this WE and share.

Regards
Jan P.

[eblc1388]

I commented in my previous post about the GAL16V8 IC, which if failed, the whole power supply would be dead. In the weekend I tried to tackle this last problem by tracing out the inputs/outputs connections of GAL16V8. The good news is that there are only five inputs signals and four output signals. The inputs are /RD, /WR, A13, A14 and A15. The outputs are to LCD module, 81C55 PPI , 6116 SRAM and NAT7210 GPIB controller IC.

Connecting a logic analyser to both the inputs and outputs reveals that they only share a combinational relationship, as the clock pin of the GAL16V8 is connected to /RD instead of a clock source. The analyser waveform also indicate when exactly will each output changes as per the inputs changes. This provides the address space information. Without the need to remove the GAL16V8 from the circuit board I managed to replicate its function via doing a similar design in wincupl. This software is now free from Microchip and allow the compiling and simulation of the logic functions in a PLD design file. It also produces a .jed file for programming the GAL too. Though I haven't remove the GAL from the board, I'm 99% sure my design file will work as it's simulation is correctly compared against the actual logic analyser results.

Judging from the photos of different Motech power supplies from the internet, the masterboard all look the same as mine, with the ICs in the same relative locations on the board. So the GAL will probably works in different models too. The only difference between various models will be the firmware which define the voltage and current limits capability of the respective model.

As always, I attached all of my findings to this post. I would suggest owner of the Motech power supply to make a copy or save it up as a link. I would reckon about 90% of the information will be relevant to your model too.

Have fun! 


 

[snoozer]

You are making a lot of effort to get all that reverse engineered. When I looked through photo of your digital board it looks only different at R212 which looke to be a wire jumper on mine and the voltage regulator is bolted to the enclosure in my PSU and has no other heat sink. The name is slightly different as well PPPSZ2C.

Jan P.

[eblc1388]

When I looked through photo of your digital board it looks only different at R212 which looke to be a wire jumper on mine.

Mine R212 is a zero ohm link resistor so they are equivalent. So the GAL16V8 .jed file should work on your power supply too. They have changed the part number of the GPIB controller IC. There is no data I could find about this IC.

[snoozer]

So I have finally gotten around to read out the EPROM. Its a TI TMS27C512. Just for fun I have a quick search for strings in the BIN file and found a list of model numbers, I wonder is the firmware the same across models and some piece of hardware qualifies the limits. This would be version 8.02A.

Regards
Jan P.

PS: The picture of the display does not do justice to the actual looks, its clear and crisp for huma eyes.

[eblc1388]

... I wonder is the firmware the same across models and some piece of hardware qualifies the limits. This would be version 8.02A.

Comparing the two firmware ROMs, there are many differences while the ASCII strings appear to be the same. So they are definitely not interchangeable.

In the PPS-1204, the designer had chosen to use an EEPROM W27C512 to replace the UVEPROM 27C512. Both are 64KB memory chips. Both versions of firmware is less than 32KB, with a checksum at the last two bytes of the 32K boundary. The remaining 32K bytes in model PPS-1204 are unprogrammed "0xFF" while for the PPS-1002, they are all programmed to "0x00". I don't know why it is so except the programming time of each UVEPROM is twice as long.