PROSCAN 32" TV Model# PLCD3271A-D no power issue

[daveryder]

Hi all, I'm trying to repair a PROSCAN 32" TV Model# PLCD3271A-D, and I'm not having any success. (BTW I guess you should know right away I am strictly an amateur with very little electrical knowledge) I get no power light on front of tv, no picture and no sound. The PSU is AOYUAN model# AY118L-4HF01. I've replaced every capacitor (the dreaded Capxons) with equivalent values (Panasonic FM or FR). I get a steady 5v on standby, but with the cables plugged in all the voltages surge (or pulse) continuously, so that the meter on my cheap radio shack tester goes back and forth, rather like a metronome.

Something I noticed right away was the burned spot in the lower right hand corner by the diode D16, so naturally I assumed the problem has something to do with that. I thought it was a Zener diode, but a google search took me to this page: http://szcanyi.en.alibaba.com/produc...ode_SR560.html which identifies it as a dip schottky diode SR560 (the MIC printed on the diode apparently stands for Master Instrument Corp. a china Co.). So I ordered what I hoped was an equivalent when I ordered the new caps and installed it, but that didn't help, so I re-installed the original one, which also made no difference

On the backside of the board directly under the burned spot is what I believe is a mosfet diode, I wonder if that heated up so badly to cause the burn mark on the front of the board?

I'm uploading some pictures of the PSU and a little diagram I scrawled with the cap values if that helps.

Anyway, I would be grateful for any ideas or assistance anybody would be willing to share, I'm trying to get it fixed for my 12 year old son for a Christmas present, but right now it doesn't appear that I will be able to make that happen as time is running out. No worrys, though, mom made sure Santa is bringing him plenty of presents lol. Thanks in advance for any help, my name is Dave

[budm]

Re: PROSCAN 32" TV Model# PLCD3271A-D no power issue

Can we see the whole back side of the TV so we can see how all the boards are connected together?
Did you do the resistance test on the combination of all 3 pin on that power MOSFET?
Please also provide the pictures of the whole back side of the power supply board.
http://www.shopjimmy.com/westinghous...t-inverter.htm

[daveryder]

Re: PROSCAN 32" TV Model# PLCD3271A-D no power issue

Copy that Bud - give me a few minutes, and thank you for helping

[daveryder]

Re: PROSCAN 32" TV Model# PLCD3271A-D no power issue

Ok here are the pics - they aren't as clear for some reason, maybe I accidentally changed a camera setting - if you need cleaner pics I'll see if I can get them for you, but maybe these will work for you.

[daveryder]

Re: PROSCAN 32" TV Model# PLCD3271A-D no power issue

RE:

resistance test on the combination of all 3 pin on that power MOSFET

the only thing I could check with my cheapo MM was resistance: with - on drain and + on source it shows 0 ohms (the same as if I touch the meter leads together). Sorry if I sound ignorant, it's because I AM ignorant when it comes to this stuff

[daveryder]

Re: PROSCAN 32" TV Model# PLCD3271A-D no power issue

I've still been working on this , I have a question: in my first picture on my first post, the diode labeled D4 (right above the big 450v cap) reads infinite ohms - do I have to remove it to test it, or does that mean it's shorted? If you look closely, you can see a green goo that seems to have oozed out of it.

BTW I've ordered the new power mosfet, resistor and schottky diode located next to the burned spot, I'll update when I install them.

[daveryder]

Re: PROSCAN 32" TV Model# PLCD3271A-D no power issue

Also, on first post I said I replaced caps with panasonic FM or FR, what I meant was FM or FC series, I did read BudM's sticky on LCD TV troubleshooting.

It's odd, I've been able to fix a Dell 32" tv and a Hanspree 32" (that was a tricky one, I did what Budm said where he replaced a surface mount transistor Q7 with a through hole (2n2222 i think?) and the zener diode zd4): https://www.badcaps.net/forum/showth...1&highlight=q7

that's the hardest soldering I've attempted to date what with shaky hands and poor eyesight lol. but hey it worked - me and the boy play xbox on it everyday. so it's driving me crazy I cant figure out this proscan.

[selldoor]

Re: PROSCAN 32" TV Model# PLCD3271A-D no power issue

If you have not read it this is useful for many tests= start at post19
https://www.badcaps.net/forum/showthread.php?t=10419

[daveryder]

Re: PROSCAN 32" TV Model# PLCD3271A-D no power issue

Yes that is very informative, there is just so much info on these forums it's easy to miss gems like that. thanks. I guess I'll either start learning this stuff or my head will just explode from too much information. It's a risk I'm willing to take.