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! 

Edit: Important - Well, I'm close but the GAL didn't work. There are error in the logic equations which is corrected in later post by member Cliffweb03. Good news is the GAL now works as a replacement after using new logic equations in the design file. See Reply#19~21 for details
 

[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.

[Cliffweb03]

I've a PPS 2322 in which the GAL16V8 is a socket mounted component and therefore removable. Since I put a lot of time into repairing the analog gain-stages I wanted to see if I could replace the aging GAL16V8 which is now 10 years past the 20-year memory retention rating. I tested the GAL16V8 .jed file loaded here in 2021 by writing it to a new (old stock) GAL16V8B and installing it in the socket. Unfortunately, the PPS-2322 does not operate correctly with that newly programmed GAL16V8 installed. Has there been any other attempt to infer the logic?

[eblc1388]

The board in your power supply looks different to those mentioned above. Thus the chance that the GAL16V8 pin connections are not the same is possible.

You'll need to trace where all the pins of the GAL16V8 are going to, using Reply#10 above "MasterBoard_GAL16V8_Connections_2.jpg" as a reference. 

[Cliffweb03]

Thank you for taking time to reply! I've just finished tracing the pins for the Amrel PPS-2322 GAL16V8B and they match your drawing for the Motech PPS-1204.

Using the 2021 .jed file loaded into the new-old-stock GAL16V8B that I picked-up I ran through the input space and read the output pins.  Attached as an image below is a table of the Input/Output states measured, I've used * to denote when the input state doesn't effect the output.
                           
While the power supply was inoperable with the new .jed-loaded chip, the LCD was producing appropriate text. In the below table, the LCD enable goes high exclusively on the input pin state that you identified (though all the other chips are also enabled). As such, I think that there's good odds that either I've got a bad batch of GAL16V8B chips or there's some subtle error in going from the logic equations you identified, to the .jed file. I've got a couple more new-old-stock GAL16V8B chips on order from another supplier. Could be a couple weeks until I can test them. (edit: there were errors in my measurements and assumptions, resolved below in latter posts)

[eblc1388]

In the above table, the LCD enable goes high exclusively on the input pin state that you identified (though all the other chips are also enabled).

The ENABLE signal for the LCD is different from the remaining chips. It goes HIGH to enable the LCD to take in the data. For the other three chips(SRAM, NAT and 81C55), a LOW is required on the CE or CS pin. Therefore, the outputs you've obtained from the GAL16V8B looks correct to me. The RD and WR line from the MCU cannot be both low at the same time so you'll need to test them separately, placing a LOW on either one at a time. The output from the GAL should be identical to the measured state you did before. (see table attached)

If you do get the same result as shown in the table, I can't think of any reason why the replacement GAL would not work, unless the designer had change/swapped the decoded line to another address combination. The only way to find out is to connect a logic analyser to each chip to verify the address lines state when the CS signal goes LOW.
 

[Cliffweb03]

GOT IT! Tested and working in hardware. The logic equations you identified were very close to what's in use on the PPS-2322 and I would not have gotten here without your help. It might be worth re-checking the (below) equations against your waveforms. The only difference was that the NAT, PPI, and SRAM chip select must be independent of the RD or WR.

LCD  = A15 &  A14 &  A13 & (RD # WR) ; 
NAT  = A15 &  A14 & !A13  ;
PPI  = A15 & !A14 &  A13  ;
SRAM = A15 & !A14 & !A13  ;

[Cliffweb03]

Design Files and burn-ready image for the PPS-2322 GAL16V8B as a .zip below. These should also burn to the ATMEL version(s) of the 16V8B available as new stock from the typical electronic parts catalog companies.

[eblc1388]

You are absolutely correct with the changes. I should have pick this error up but the GAL chip on my power supply is soldered and I did not bother to remove it for replacement testing. Looking back at my previous logic analsyer results, it is previous obvious that the chip select signal must be ahead of either the read or write signal in order for the chip to work. It is a silly mistake on my observation.

The simulation below, of the modified equations match with that of actual logic analsyer results. Thanks for letting us know the replacement GAL actually works in the power supply.