A GW Instek, PSP-405, Lab bench power supply repaired

[jeka1981]

So, from start :
 - i bought a faulty PSP-405. It had problems something like in this video :


but dimmer and like resetting itself + beeping .
I replaced almost all capacitors, except all 50V - C53, C19, C16, C10, C7 and C48 100V 0.47 mF ( i didn't foun them at the moment) but nothing changed.
I almost gave up, but after i replaced last 2 capacitors ( C9 and C12) - it resurrected.

I hope this will help someone !!!

[mahmut47]

lm358 is not working can i replace with lm358n or lm358p ?

[mahmut47]

can you show me where is the c12? my power supply always resetting icant fix it

[Kean]

can you show me where is the c12? my power supply always resetting icant fix it

I don't know the capacitors designations, but on mine I had to replace the two 470uF 25V caps between the heatsink and smaller yellow transformer T1.
See attached pic, you can tell the caps are bulging on top.

[jeka1981]

This is C12 :

[Kean]

Thanks.  I have another two of these to fix (Iso-Tech branded from RS), so will change that cap as well.

[mahmut47]

there is no cap at this c12 socket. my power supply always resetting itself. i just change lots of companents but still not working i dont understand what is the problem i need help 

[mahmut47]

i need help please someone tell me how to fix it. i tried everything but still my power suppy restarting

[wraper]

Does you power supply actually have SMPS problem or it just restarts while 5V low power SMPS is working fine? There are at least two major revisions of these PSUs, the major difference is that in newer PSUs there is no separate large CPU (digital) board besides SMPS board and CPU is on a front panel (2 PCBs instead of 3 in older ones). And some small differences in SMPS board. I've seen reboot loop in newer version due to EEPROM corruption.

[mahmut47]

my front panel %100 healty cuz my other psu board works normally with the front panel but second one makes it restart 

[Bernique]

Hello all,

first post on this forum... where I landed after googling from France for faulty PSP-405

I spent a couple of hours reading here and there, made some tests, but still requesting some support to have this power supply back to life. This is the main reason why I'm using this very helpfull post started long ago 

Resume of the situation:
I received my Instek PSP-405 from a friend who pasted away recently, which is my main motivation to repair it
I tried to power it up: I had a normal screen on for a second, and then it turned blank (only backlight).

Based on my reading, I checked the best candidate capacitors (C49, C25, C29 & C33) and C29 was found totally scraped (33pF with a nice blown top!), while the others were within 10% of their original value (with ESR around 0,8Ω)
To stay on the safe side, I decided to change C25, C29 et C33 as I had some stock. I put C49 back in place (no spare).

After this, I now can recover the normal startup with the expected screen. I can select values (V, I, P)... all is fine
Almost fine
... 'Cause when pressing OUTPUT ON, tension is rising up and going back to quite zero

What's next?
Before trying to dig into the EEPROM (some other readings ), I made a visual inspection of my power board... and found that IC2 (COSMO 1010) is quite dirty/over heated? (and connected to C29).
I also scope the output while OUTPUT is OFF... and go a nice signal from the main with 50Hz frequency (and confirm that output is quite zero with the same signal whatever OUTPUT is ON or OFF!)
I tried to identify this IC2 on the schematics given in the various post but couldn't find my way... sorry for being so novice

My question:
I suspect this IC2 to be part of my problem (I belive it is supposed to command high voltage and being faulty could lead to let the 50Hz going everywhere it should not!). Does anyone of you with better expertize then mine could confirm this diagnostic or give me another track to follow?

PS: I have attached a few pictures for reference below... but can provide some more detail if needed

[wraper]

With this newer version of PSP-405 hardware, EEPROM corruption most likely is the root cause for screen going blank. As I remember broken calibration data caused an issue like yours.
I attached a working EEPROM dump, image shows bytes responsible for calibration. Calibration data is likely corrupted in your EEPROM, but you can try copy it all or partially (if copying all results in return of failure) into working EEPROM dump. The problem with this hardware version it that unlike in older units, adjustment mostly happens in firmware unlike in older units that had another large PCB besides SMPS PCB and that used potentiometers only. I attached old adjustment manual I found on internet in the past for reference. GW instek refused providing me such for new HW. So I adjusted mine by fiddling with cal data in the EEPROM, IIRC voltage calibration consisted of two ranges, 0-20V and 20V-40V. Don't remember about current but likely there were two ranges too, each consisting of 2 bytes. IIRC potentiometer on SMPS PCB was for zero current adjustment.

[Bernique]

Thx for the quick answer

EEPROM will be a new field for me
I have an EEPROM reader branded LEAPER-48 from my aboved mentionned friend... I will first try to identify the PSP-405 EEPROM on the front board, check if my reader is compatible and then remove it if possible in order to read it.
I will also source a fresh one in case of... as well a new COMOS 1010 and low ESR capacitors (from Panasonic if any) in order to justify shipment fee

[Bernique]

According to this post, EEPROM should be AT24C08B from ATMEL.

I can have some other references from my usual vendor but working voltage start @2.5v. The ATMEL chip seems to be tolerant from 1.8 to 5.5v, but what about the voltage used in the PSP-405? Any idea please?

[wraper]

I'm pretty sure it's 5V.

[Bernique]

Hello,

I took part the front panel and checked for the EEPROM.

Reference is the following on top of the SOIC-8:
   ATMLH702
   08CM     Y
   .A8ND6A

Found hard time to find any datasheet on this (I don't even know which references are relevevant to seach for!... atmel 08CM seems promizing, but then I'm stuck!)... do you have any info on your side please?

[wraper]

08C = AT24C08C

[Bernique]

desoldering is done

Without any adapteur, I had to solder some leg extentions to the EEPROM in order to plug the chip into my reader (see below picture) 

Bad news is I cannot have my old LEAPER-48 running under Ubuntu, neither on an old WinXP (some .ini file missing... I gave up!)

I took a look on the web for a new reader... and identified the XGecu T48 (TL866-3G) programmer (TL866 3rd generation)
Any other recommandation for Christmass for a EEPROM reader with reasonnable (chineese) price, capable to read the above chip as well as AT24C08 ones under Ubuntu distro (understanding I'm an occasional user, it's not my daily sport!)?

[wraper]

The cheapest would be something like CH341A programmer. With DIP->SO8 ZIF adapter will cost like $5 delivered.

[wraper]

Bad news is I cannot have my old LEAPER-48 running under Ubuntu, neither on an old WinXP (some .ini file missing... I gave up!)

Did you install a separate driver? Also there are different program versions available. Should support any 32 bit windows from win98SE to Win7.

[Bernique]

I did.
The reader is recognized by the WinXP laptop as weel as the soft (Universal IC Writer).
I can lauch it, but a popup indicated a missing .ini file and the librairy for the eeprom is empty

from there, I cannot read the eeprom

[wraper]

I can lauch it, but a popup indicated a missing .ini file and the librairy for the eeprom is empty

Did you install the IC library that comes separately?

[Bernique]

oups... I missed that I believe
On the CD I have with the reader I do not have any additional lib... sounds like Google time for tonight

By the way I was reading stuff on CH341A programmer... old version seems to request mod not to smoke 3.3v chips, new ones seems more friendly...
Very interesting : https://www.eevblog.com/forum/repair/ch341a-serial-memory-programmer-power-supply-fix/msg5198676/#msg5198676

[wraper]

Why would you install some obsolete garbage from CD? https://www.batronix.com/shop/programmer/leaper48/index.html?gclid=Cj0KCQiA7OqrBhD9ARIsAK3UXh23J-Xt2l1pijISSH9Si5BXaRXDjko-sXUKIl8MXqhsIJbi8lfKBIUaAtN3EALw_wcB in downloads tab

[Bernique]

Thx, I was exactly on the same page