Samsung PSU BN44-00162a Repair

[satinser]

Just repaired one of these usual problems with s/c components QX801 and QX802 plus associated SMD components. Lasted about 10 minutes and blew again. Suspect overheating, just repaired again does anybody know what the working temperatures should be on QX801 and 802 when TV has been on for over 30min.TV concerned is PS50Q97HD.
Would like to test it this time with IR thermometer to monitor potential overheating.

[flocko]

Re: Samsung PSU BN44-00162a Repair

Hi what did you use to replace QX801/2 Samsung used to fit W20NK50Z with the built in Zener diode but later boards had 18N50 / 20N50 fitted, i fit W20NK50Z what ever is fitted and buy in from Chine less then a £1 each also found on Samsung Y/X Sus boards Flocko

[tom66]

Re: Samsung PSU BN44-00162a Repair

I presume you used proper thermal paste on the new devices and made sure that they were isolated from the heatsink using a mica spacer or buying a part which is isolated.

On some of these PSUs, it's very rare, but the FETs popping can damage the driver. It is transformer-coupled so it is a lot rarer, but you could consider replacing a few of the transistors around the driver ICs.

Also check the Vcc supply for the driver boards, Vsus output voltage OK & PFC bus voltage OK too.

[satinser]

Re: Samsung PSU BN44-00162a Repair

Thanks for both your replies. FETs fitted were FPQF-9N50C. Yes thermal paste was used. Been working on test now for last 1hour with fan temp placed towards the PSU to cool the FETs. Temp at moment around about 31c as read from fet body.So far so good. All voltages have tested fine. As a matter of interest have tested temperature of FETs on BN44-0161a fitted to the 42" model that Ive just repaired and after 1 hour they were upto around 60-65c obviously without the fan. These power supplies would obviously benefit with fan cooling as the Panasonic have!

[flocko]

Re: Samsung PSU BN44-00162a Repair

Sorry getting my QX and QS mixed up if this is the 50" board use the 11N50 (11 Amp 500v) as the 9N50 are only 9 Amp rated for the 42"that could be your problem with a white screen you push them over the top Flocko

[satinser]

Re: Samsung PSU BN44-00162a Repair

How did I make that mistake just checked circuit diagram and as you say they should be 11N50C. Will have to order some although I have got some 13N50C do you think they would be ok?. Many thanks for putting me straight!

[flocko]

Re: Samsung PSU BN44-00162a Repair

Hi again as said before when repairing these boards for 42"or 50" i use 11N50 for QXs and W20NK50Z for QS, if you do lots of power board and Sus board repairs buy them in from China and save your money and have them is stock Flocko

[satinser]

Re: Samsung PSU BN44-00162a Repair

Yes I do buy components from China from their Ebay equivalent AliExress.com only drawback is the time it takes for shipping.
Do you think 13N50C would be ok to use? As I said Ive got some in stock and it will save on the waiting time for this repair.

[tom66]

Re: Samsung PSU BN44-00162a Repair

Many transistors from China are faked. Be careful.
http://sound.westhost.com/fake/counterfeit-p2.htm