Help with 17PW26-4 PSU repair

[cheeky2]

Ok been reading a fair bit out this psu and the failures of it. I have no 12V or 24V under load. The other voltages are as they should be.
The common diode failure D893 UF5402 is OK and has been replaced (just in case it was leaky) together with checking the resistor R1036 0R.
I have found under no load the 24V and 12V are present however as soon as it connected with main board and inverter it drops down to around 1V.
It is looking towards the FAN7711 failure. The main cap has around 290V across it.
So any help isolating it further would be good. Seen a few videos on youtube regarding other issues however checked there relevant component failure and components are ok.
It did have a smd diode or cap non soldered on one side from manufacture. Though this didn't rectify issue. See attached picture. I did find C874 have a high esr which was replaced 40ohms and leaky.
So any thoughts with isolating fault further?
Thanks in advance Anthony

[dick_barton]

Re: Help with 17PW26-4 PSU repair

The main cap (C819) should have more voltage than that across it so check Q803, D882 and the components around IC802 (FAN7529)

[cheeky2]

Re: Help with 17PW26-4 PSU repair

Sorry the main cap was 390V just checked again under load as realised I checked it only under no load originally. I mistyped original post it should have read 390V instead of 290V!

[dick_barton]

Re: Help with 17PW26-4 PSU repair

So your PFC circuit is working and giving a decent voltage.
Now check Q813 & Q814 and the resistors around them. R860, R861, R864, R865 also diodes D891, D892, D875, D894.

[cheeky2]

Re: Help with 17PW26-4 PSU repair

Mosfets not shorted, no D891 or D892 all other mentioned resistors are within tolerance. No D875, D894 is fine.
Thanks for your time helping

[dick_barton]

Re: Help with 17PW26-4 PSU repair

Mosfets not shorted, no D891 or D892 all other mentioned resistors are within tolerance. No D875, D894 is fine.
Thanks for your time helping

I can see D892 has not been fitted so probably D891 is not fitted either.

Do you have the 3.3V and 5V standby?
If you do remove the mainboard and on the power supply connect a 1K resistor between 5Vstby to Stby and then check for 12V/24V

[vinceroger69]

Re: Help with 17PW26-4 PSU repair

This pdf has some good information regarding the psu

[cheeky2]

Re: Help with 17PW26-4 PSU repair

OK whilst checking the FAN7711 IC on pins 5 and 6 I managed to blow the 2 mosfets q813 and q814! So need to order them and fuse (I will check other components just in case blown them as well)
The power supply did get all good voltages when inverter disconnected. Which then lead me to conclusion that inverter was shorted out causing the 24V and 12V to drop. However I didn't originally think that this was the problem as I expected the fuse to blow on the inverter before dragging the psu down.
However I was wrong as I have just checked the mosfets on the inverter and have a found a bank of 4 shorted out! Inverter is SSI_400_14A01 EREV.1. So am guessing the power supply wasn't the issue but the inverter dragging the psu down!
I think I have the Mosfets suitable already and will change the SEM2107ic as well just in case.
I will keep you updated on what happens...

[vinceroger69]

Re: Help with 17PW26-4 PSU repair

https://www.badcaps.net/forum/showth...hlight=SEM2107
http://www.ebay.co.uk/itm/4614-Inver...IAAOSwHaBWiobD
http://www.ebay.co.uk/itm/SEM2107-IC...gAAOSwl9BWK3AK

[cheeky2]

Re: Help with 17PW26-4 PSU repair

Thanks I had read about the issues with these inverters, but just expected the inverter fuse would blow first before dragging the psu down!
Mosfets replaced on inverter now however need the mosfets for the psu! So just about to order them with sem2107 ic.
I will let you know what happens with repair in a few days time when parts arrive ....

[cheeky2]

Re: Help with 17PW26-4 PSU repair

After replacing 4 mosfets and sem2107 ic and sorting out psu after blowing the mosfets and fan7711 ic it is all functional again (the blown mosfets and ic on the psu were down to me when testing!)
Happy Sunny Days
Thanks for all your help

[vinceroger69]

Re: Help with 17PW26-4 PSU repair

Thanks for the update glad the sets working its good when we can fix boards down to component level as its so easy to change to a replacement board