GW Instek PSP-603 60V 3.5A power supply (short) review and teardown

[nctnico]

Currently Toploser seems to need more money and he does that the only way he knows how: by selling equipment for excellent prices. This landed a GW Instek PSP-603 on my desk. It seems like a good addition to my lab as a compact general purpose power supply.



The operation is a bit more complicated but it can do some interesting things. Vlimit sets the maximum output voltage. Unlike many other PSUs the output voltage cannot be set (using Vset) above Vlimit. There is also a current limit and a power limit. The power limit adjusts the current limit. In the end something has got to give. The 'Normal' button saves the current settings for the next time it is powered on. I measured the AC output leakage voltage referenced to ground to see if it has half the mains voltage at the outputs but that isn't the case. I measured about 2V (high impedance).

The power stage:


The front panel:


A MSP430 microcontroller runs the entire thing:


Optocouplers for the serial interface (which isn't a real RSR232 interface; a special cable is required):


'RS232' connector:


The fan is temperature/load controlled. At first it made more sound than I liked but some rubber fan mounts solve that nicely:


So far the only logo I found on the board:


Unfortunately it seems these power supplies have some issues with the capacitors:
https://www.eevblog.com/forum/repair/a-gw-instek-psp-405-lab-bench-power-supply-repaired/
However the internals look radically different. The version shown in this thread has a seperate processorboard with a through-hole 8051 microcontroller which explains why my one has so much unused space:

[crispus]

I do have this also, but not yet functional.
The switching transistors are shorted.

Anyone knows a good replacement for 2SC3320?

[woody]

Congrats, looks like a nice catch. I see that the rubber fan mounts are put to good use again   Maybe I'll get some for the fan in my 2204E, although its noise does not bother me (yet).

[Fraser]

I have three of these power supplies and they have been providing excellent service for several years.

Mine do have one annoying characteristic though....... poor visibility of the LCD display at some angles. I normally have my power units at eye level or higher and they are fine. If I view mine from above, looking down on the display from an elevated angle anywhere higher than straight on, the display becomes unreadable.

I suspect this issue has been sorted out in more recent releases of the power supply as it is annoying to the user.

Fraser

[nctnico]

Today I did some testing to check the accuracy of voltage and current readouts. On my unit the voltage readout's acurracy is better than 0.5% across the entire range. The current readout however isn't that good. At 100mA the error easely reaches 5%. It gets better at several amps where the error drops below 1%.

[Hydrawerk]

This GW Instek PSP-603 is similar to Manson PSUs. https://cdn-reichelt.de/bilder/web/xxl_ws/D500/SDP-2450.png

[nctnico]

This GW Instek PSP-603 is similar to Manson PSUs. https://cdn-reichelt.de/bilder/web/xxl_ws/D500/SDP-2450.png

Similar yes but definitely not the same. It wouldn't surprise me if they come from the same factory but they are not the same product.

[c_04]

Hi
I have also this power supply but mine uses 8951 uC with separate board signed as DPS4005. Is there anyone who could share bin file for this uC. Today ive checked - my is blank. I can share bin file for eprom if needed. My is 27C512 rom is V.1.89.
Regards
Greg

[wraper]

Hi
I have also this power supply but mine uses 8951 uC with separate board signed as DPS4005. Is there anyone who could share bin file for this uC. Today ive checked - my is blank. I can share bin file for eprom if needed. My is 27C512 rom is V.1.89.
Regards
Greg

Please do not make the same post in 4 treads. As of 89C51 being blank, it should be read protected, not blank.

[c_04]

My device doesnt work - maybe thats the reason why i see blank 8951.
Cheers
G

[wraper]

My device doesnt work - maybe thats the reason why i see blank 8951.
Cheers
G

You won't be able to read it be MCU faulty or not if it's read protected. Because of that nobody will give you a firmware dump, simply because you cannot read it. Also that's a rather stupid reason to assume there is something wrong with MCU. There may me a hundred of other reasons why it does not work. You did not even tell anything about fault symptoms.

[c_04]

I have everything on lcd and any buttons do not react. 5V is present on dps4005 board. 8951 is controlling both: Lcd and keyboard + also DAC.
You are absolutely sure they uC is copy protected? I realize that lock bits exist but its not a must to use them. And i have to say that ive seen AT89C51 in some supplys. That means they used different manufacturers. But who knows the truth? Did you tried its copy protected?
Thanks for reply
Cheers
G

[wraper]

I currently have only newer revision of this PSU which have different control board. But it's very rare occasion when manufacturer does not enable read protection, so you can be pretty sure about it.

I have everything on lcd and any buttons do not react.

Don't quiet understand this sentence, is there anything displayed on LCD? IIRC there was some IC on front panel board for LCD and key control.

[nctnico]

Did you buy the PSP-603 new or second hand? Can you make a picture of the PSP-603 when it is on? I don't understand what you mean by 'everything on LCD'. Do you see numbers or are all the segments on?

In my experience with repairs a failed microcontroller is extremely rare so I would look for other causes first. Perhaps you can take some pictures of the circuits as well. Maybe others can spot a problem or something to check.

[c_04]

It means that every symbol is lit on when supply is turned on. Everything stays no matter what you do.

[nctnico]

It means that every symbol is lit on when supply is turned on. Everything stays no matter what you do.

I'd start by looking how the front panel is put together. I suspect there is another microcontroller in there. I also notice that it seems there are two microcontrollers on the control board. Probably one for the regulation and the other for the user interface.

[wraper]

You should check if there is oscillation on MCU xtal. Also take out front panel PCB and look what's on it. IIRC there is no direct connection between MCU and LCD and keys. Also it may fail to start normally if EEPROM content is corrupted. You could try powering it on with blank EEPROM IC.

[c_04]

Display and keyboard board has only PCF8576. Entire keyboard goes directly to 8951. That another uC 8032 looks like some protection unit and receiver for remote control.
I will check once again whats going on with external power supply to power on only dps4005 board + control panel. I will see that helps and as one of you said - i will try to remove eprom. But previously ive removed that second uC and nothing changed.
I asked Gwinstek to any help in servicing and they didnt even answered. I asked Farnell where this power supply was purchased - it was i think 2007. They said that if its warranty has passed they cant help. I asked local 2 stores. In one they service only items which were bought from their store... others said thats too complicate fix for them - they dont hold such data. Im waiting also for another replys but i think as always...
Cheers and thanks for your kind help
G
P.S. Ive attached kind of service manual, because its for different power supply but its mostly the same. At page 7 you will see control panel. Pages 2 and 6 shows boards with uCs. I dont know which is closer to my power supply. In fact ir doesnt matter yet because im not checking other parts and tracks. Anyway i think i will need.

[c_04]

I must say one of you were right. When i remove Eprom i see blank lcd. So - possible data corrupted.

[nctnico]

Those schematics look interesting. If your front panel also has a PCF8576 then the schematics will be very useful to debug your power supply. I'd start by checking the crystal with an oscilloscope and see what the reset pin is doing.

[wraper]

I must say one of you were right. When i remove Eprom i see blank lcd. So - possible data corrupted.

I was meaning 8pin EEPROM, not EPROM. But at least you can assume there should be some life in 8951. And not remove EEPROM but erase it (with backing up first) or replacing with another IC. Calibration data and settings are stored inside it. EPROM might be corrupted too but there is much higher chance for EEPROM as data is written to it quiet frequently and something might go wrong during that.

[c_04]

Ive attached pictures you asked. As you see - everything means everything .
If you mean restet is SW1 - which is missing switch. Hmm it resets display for while. If i turn on again power supply then everything is back as it was previously. Just a question: if i erase 24c02 eprom then how i can bring back calibration data? Or how to calibrate this supply? I dont know what to do if data will be corupted. Is there some special line where calibration is stored? To me it looks rather simpler - there are stored user settings. I remember that once or twice in the past this power supply was beeping and display was showing something, of course i wasnt able to change nothing but then supply pcb was unscrewed. When i screwed it back lcd stays as is right now.
Cheers
G

[nctnico]

You have to debug this step-by-step. Do you have an oscilloscope? Preferable a digital one. Besides checking the crystal and reset pin you can look at the I2C bus. Maybe one of the I2C devices isn't responding which locks the entire thing.

[c_04]

Yes i have oscilloscope. But im not sure its only 10MHz. Hmm... looks that i have to contact with my friend. So im now suspended. Anyway - i will try to copy 24c04 content. I will do it later because i have to prepare for it. I2C looks that only use 2 devices: one is 24c04 and second PCF8576. I dont see nothing more on this bus.
Thanks again and cheers
Greg

[nctnico]

10MHz is good enough for I2C. Are the SCL and SDA lines both high? What happens at startup? Any activity at all? Before pulling any chips out it is better to diagnose first.

[c_04]

I unsoldered 24c02B and still nothing. Without this memory i hear only 2 beeps and thats it. Erased and soldered back. I tryided to copy content but i made mistake and i lost it. Now i will check maybe something with oscilloscope. Not much to do with 10MHz tool. But maybe...
I will try to burn another 27C512 with my copy but i dont belive it can help.
Maybe someone of you have working one bin or hex?
Cheers
G

[wraper]

Erased and soldered back. I tryided to copy content but i made mistake and i lost it.

At least for this older PSU version there is calibration manual available.

[c_04]

Thank you very much.
I didnt moved any pots - should stay calibrated.
Checked with oscilloscope. Theres something. SCL and SDA - at least higher level than 0V when turning on. Not see peaks or something like that but maybe because of my oscilloscope. Also xtal looks present but in similar way.

[nctnico]

Are the SCL and SDA lines at 5V after the PSU has started?

[c_04]

Im not sure its showing me correctly but its rather 2V. Will check again with multimeter maybe too.

[c_04]

With multimeter both shows 5V. But constant i think.

Hmm at different pins of U1 i see some activity. I thought that this uC is dead. Now looks opposite. 7832 it sends only some noises. I have somewhere 8031 but has only half of ram 8032 - i cant check it that way.

[wraper]

Thank you very much.
I didnt moved any pots - should stay calibrated.
Checked with oscilloscope. Theres something. SCL and SDA - at least higher level than 0V when turning on. Not see peaks or something like that but maybe because of my oscilloscope. Also xtal looks present but in similar way.

It's a mix of digital calibration + pots.

[c_04]

Ive bought 5pcs of P80c32 for other projects and i will try to check if that will work in this power supply. I will check once more 27c512 - yesterday i was able to read it but im not sure about today. Ive checked closer whats happening to and from 27c512. Looks that both processors are sending and receiving something. When i short SW1 then starts some activity on SCL and SDA. Normallny is flat line there. After turning on is there send high and goes back to flat line. Shorting SW1 only 2 times produce similar effect after that when i try to short again nothing happening. Checked 74hc373 and looks fine. No idea what else i can check.
There must be something working because ive seen twice fan was started and after some time stoped.
Cheers
G

[c_04]

Hello Guys
My way of thinking was good but not that chip was damaged as i thought. Today ive got 80C32 and i replaced old one 78c032c from Winbodond. After short boot my power supply wake up after probably 10 years lying on some storage.
So real thanks for each oneof you who forced me to make some measurements. Without you probably i would be sure that this power supply is unfixable.
Thanks very much again and...
Cheers
Greg

[nctnico]

Thanks for feedback about the actual problem! These power supplies are quite nice.

[c_04]

But unfortunately customer service is crap. Manufacturer doesnt reply for any questions.
No one wants to service these power supplies. Farnell said that if its still under warranty they can help. Similar TME in Poland - they said that they can fix it only if it was purchased in their store. I asked many other services that spacialise with measurement gear. All of them said that they are not able to fix this power supply. At last when i was pissed enough i started to dig there. In fact is not much inside. And if any uC is good should start just by the kick. Anyway i start to think - what can be reason if LCD doesnt work and any entered values do not makes response. As i thought was uC... next you know
Cheers
G

[c_04]

Hi
Ive observed another issue. Power supply is occasionally reseting. I checked some capacitors C25 (i think), C29, C33, C37, C49, C36 - replaced this one with Sanyo. This power supply probably was previously serviced because all caps are like new. What else could be the reason of resetting? Once even i wasnt able to set any value because constant resetting but then i pressed wire connectors and everything back to occasional reseting.
Maybe its somehow connected with that i replaced 78C032 to 80C32?
I will replace eprom maybe... but no idea it can help.
Cheers
G

P.S. Interresting... when ive replaced eprom with 27C512 (UV erasable) power supply is reseting even when i try to sen any value. That means there something is too slow. Maybe I need 80C32 little faster. Maybe thats the reason.

[c_04]

I must say that there is definitely something wrong with contact between uC and socket. I replaced uC with another one and everything is back to normal. Checked another eproms (UV) and every of them works fine no resetings. I replaced back again the same uC which was before this test and works as a charm.
Of course this dead 78c032 is still dead
So thats another point - bad contacts and weak quality sockets.
Cheers
G

[byhazin1453]

HELLO, I would be glad if you can help me know the reason for this problem on my device.