viewsonic 32in lcd tv power supply broken

Guest · Posted: Mon Apr 11, 2011 8:34 pm Post subject: N3251W Randomly Shuts Off/On

So i have been thru this whole thread and i see different issues with the power supplies on this tvs. However they are either completely dead power units or they just wont turn on. The problem im having with my Tv is that the unit does power on and works just fine but it could be 10 mins, 5 mins, 2 mins or sometimes 30 mins and the Tv will just turn off on its own. The oposite also happens if i leave it off it will turn ON by itself. Any ideas where could the problem be?

Thank you very much.

train123 · Joined: 26 Jan 2010 Posts: 88 Location: Canada

Did you check for poor capacitors in the power supply? The top of a capacitor should be perfectly flat so look for bulging. A poor capacitor will provide poor filtering to the micro and this can lead to a confused micro and random events are the result.
A second thing to check is the power button on the front panel. I've seen the button worn out and the result is that the power switch is hovering between on and off. Try loosening the 4 mounting screws for the power board to free up any pressure on the power switch.

Knight2000 · Joined: 11 Apr 2011 Posts: 1

I did check capacitors and i have replaced a couple of them already but the problem still there. I will try the button approach and will get back at you.

train123 · Joined: 26 Jan 2010 Posts: 88 Location: Canada

Did you change the cap because they were bad or were you just guessing?
If the caps were bad then you should have found more than just a couple.

Guest · Posted: Sat Apr 16, 2011 6:30 am Post subject:

I did find 2 caps that were bulged.

train123 · Joined: 26 Jan 2010 Posts: 88 Location: Canada

You'll want to check the voltage going to the video/processor board. Bad caps will cause damage to ZD4/Q7 and they may not be functioning correctly. You should see +5 and +12 volts. Anything less than that, the processor will be erratic.

910pcsupport · Joined: 21 May 2011 Posts: 2

hello does the fsp271-4f01 power module also use similar ic's for the 24 Vdc inverter source?

i have a olevia 42-lcd which powers up but gets no inverter voltages. please advise Razz

Guest · Posted: Wed Jun 01, 2011 2:56 pm Post subject:

Thanks for all the info on this site. It was a good source.
Let me say that I have N3251W with bad power supply (FSP212-3F01.
I replaced all the bulged caps, and there were several.
I replaced and found bad ZD4 and Q7.
5Volt good(green light would now go on pressing on button, but no 12 or 24.
Found unusual voltages around controller IC L6598D per data sheets and literature on the net. Replaced and all ok.

Thanks again, Rob

ajvdwest · Guest

Hi all,
Thanks for all the info!
I also have a dead FSP212-3F01. (from Wharfedale 27" TV)

Replaced buldging and all other caps, replaced Q7(was shorted).
ZD4 and ZD3 was still in tact but replaced ZD4 anyway.

Still no power on secondary side. All other components seems to be fine except I measure 51ohms across D2 and D3 which does not sound good.

Can anyone please tell me what are the part numbers of D2 & D3?

Regards,
AJ vd Westhuizen

ajvdwest · Guest

My bad, they're supposed to measure the 51ohms.

Any ideas as to why the board could still be dead after symptoms and replacements as described above?