viewsonic 32in lcd tv power supply broken

TechChallenged · Guest

I too have a Viewsonic N2751w that I believe has a bad power supply (FSP212-3F01). I have replaced 14 caps with quality ones. But I cannot turn on the tv. The power button light flashes green and goes back to red. Two questions:

1. Where is Q7 and ZD4 located.

2. If I purchase a new power supply, will it have the same inferior parts? I've seen prices $50-$90. Are they the same?

Any help is appreciated.

Guest · Posted: Sat Aug 27, 2011 6:06 pm Post subject:

Q7 and the diode are on the back of the board. I beleive they are SMT devices, but I have not verified. I need to check mine as I replaced all the swelled caps (7) and the tv worked for an hour, now it is back to flashing the red/green power LED.

Guest · Posted: Tue Aug 30, 2011 1:04 am Post subject: Re: i need help too

Guest · Posted: Wed Sep 07, 2011 6:13 pm Post subject: HELP! have AC on heatsink!

Hi,
have been through all this like you have and have read about all the problems,
I have got a fsp212-3f01 board, gives standby light that is red and responds to power button turning green but nothing from the rest of the tv, now i have tested cns1 and get 5v and 12v along the way i have also replaced all the caps as one was bulging -
The big problem i have is i have a random ac leak! the main heatsink over the bottom half of the board is live! with the power on it gives 170v ac reading - this is bad! i dunno where it is leaking from? anyone have any ideas of what i can check - it seems the heatsink share a track with some of the Q's and so i dunno if they are a victim or the cause! any advice?

confused_man · Joined: 07 Sep 2011 Posts: 3

its my post above but for some reason it didn't have me logged in!

train123_not logged on · Guest

I'm pretty sure it is normal for some of the heatsinks to be "hot" but I don't currently have a unit to verify for you. You mentioned +5 and +12 to be there but there is no mention as to +24 for the inverter drive. As well, you should see a "turn on" signal going to the inverter on the same connector. Also try shining a bright light onto the screen to see if you can see any images on the screen while the set is on.

confused_man · Joined: 07 Sep 2011 Posts: 3

I'm pretty sure it is normal for some of the heatsinks to be "hot" but I don't currently have a unit to verify for you. You mentioned +5 and +12 to be there but there is no mention as to +24 for the inverter drive. As well, you should see a "turn on" signal going to the inverter on the same connector. Also try shining a bright light onto the screen to see if you can see any images on the screen while the set is on.

thanks for the reply - i actually checked on a different tv and yeah the heatsinks are live! really crazy!
Yeah, theres not any 24v on the inverter at all, the 12v is actually 11.83 but i think that should be fine, I have changed all the main caps and that hasn't made any difference, the led is red and then when power is pressed it goes green and the 12v kicks in. Now i have looked through th thread and found mention of ZD4 and Q7 but mine don't appear to be shorted, my Q7 gives 19v on the collector if i remember correctly when the other two pins are 13v -ish the Q11 doesn't seem to be behaving tho - in this thread it says it should have 13v on its collector when the set is turned on but mine doesn't manage above 5v, so i am going to replace that tomorrow and see if that makes any change - if not will prob go for the rest of the kit from ohmes....
Any thoughts ?

train123_not logged on · Guest

You are on the right track, I originally posted the Q11 fix. Q11 supplies the power for the IC's controlling the +12/+24 outputs.

confused_man · Joined: 07 Sep 2011 Posts: 3

Well... i replaced those q11, also did some other bits - trying to emulate the repair kit on ohms website, and then powered it up and i got nothing! not even the blue light i had previously... so i decided to start probing around and see what voltage i had where... there was not standby voltages - i had lost those! but i had ac coming in, i was probing near Q4 when i must had been close as there was a spark and it has killed ic1, ic2 and R29... maybe others but they look bad, so going to have to replace those and then start again! had hoped replacing the original stuff would get me going but back to the drawing board!
Is there anywhere to get replacements from easily?

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

Usually Digikey can supply most parts. You might want to consider replacing the whole supply instead.