Electronic equipment repair and service manual search discussion :: Topic review - ATX power suply LC8700 doesn't work (+5V) ICs PS229 and wt75

Iuly · Posted: Wed Mar 21, 2012 12:10 pm Post subject:

I have the same problem too.

Guest · Posted: Tue Oct 27, 2009 4:58 pm Post subject:

Aha, now I see... but I don't know the solution. Maybe I have the same problem... I will see.

Guest · Posted: Tue Oct 27, 2009 9:31 am Post subject:

yes I understand, but it worked on my pc before and now same psu wont start computer :S

dr.1m · Posted: Mon Oct 26, 2009 2:27 pm Post subject:

Even I didn't find any schematic. Anyway, I don't aspect it any more.
Did you understand my answer? Do you use it on a new PC? Because it seem that it can't work on oldest PC.

Guest · Posted: Mon Oct 26, 2009 1:54 pm Post subject:

I dont have stable 5 and 3.3v but when on the output of 12V is a load that consumes 1A the 5V voltage output is stable, but the bigest problem is schematic for this kind of PSU because I can't find any :S

dr.1m · Posted: Mon Oct 26, 2009 1:02 pm Post subject:

And what is your problem with it, anyway?
I found that maybe the my PS doesn't have any problem, but I didn't tested it on new PC yet.

Guest · Posted: Sun Oct 25, 2009 1:52 am Post subject:

did you found solution for your problem, because I have the same problem with my PSU lc8850 :S

dr.1m · Posted: Thu Sep 25, 2008 7:00 am Post subject:

Until now I haven't found any deflects. Probably is that the power supply is good, and I'm trying it in a wrong way. Why?
I know that the ATX power supply work only if they have a load on 5V output, but here it seems that not so. Why?
When on the output of 12V is a load that consumes 1A the 5V voltage output is stable. At least until 12A.
It's possible that the power supply has working conditions other than the standard ATX. It means that it's run only if there is a load placed on 12V output instead of 5V output? Rolling Eyes

dr.1m · Posted: Wed Aug 06, 2008 7:58 am Post subject:

vtech thank you.
Till now I find only the datasheet for Weltrend IC but nothing for other one.
The problem I have is that the 5V output don't work properly. In fact the 5V output is OK till is unburdened (without load), but the PS switch if instantaneous when I connect the load.
I checked the capacitors of 5V output and also change them, but nothing change. The interesting think is that if I connect the load before switch PS on the PS work (after switch it on) for couple of second an the switch off. In that time the 5V output is little under run:
With current around 3A the voltmeter indicate 4,9V and is litle waved.
With current around 25A the voltmeter indicate 4V and is more waved.
But with 1A load the voltage is good.

vtech · Posted: Fri Aug 01, 2008 5:29 am Post subject:

Your best bet is to try checking the electrolytics first or "try" getting a schematic which is more likely impossible? This is why I hate having to deal with chinese made yingyang crap who choose not to have any information whatsoever.
The weltrend number alone refers to a 14 pin dip? perhaps a 8pin version made just for them? and the other one is simply non-existant--even the logo seems obscure.