17PW15-9 Horrible Buzz From Pfc Help ?

[ReeceyBurger123]

This Psu is close to meeting the hammer.... Tv come in with loud obnoxious buzz coming from the back. Found the Psu to be the cause, the buzz is coming from TR806 which is the Pfc transformer I have replaced the following and the issue still persists:

Every lytic cap on the Psu including the primary
Poly caps C878, 877
Ic828 LM317T
TR806 (off another board)
Q803 Pfc mosfet
D824 Pfc diode
Ic802 Pfc controller
R817, 818, 819 Pfc resistors
R807,806 (looked burned)
Resoldered alot of devices
Nothing is S/C

After doing this it seems the buzz is intermittent either ways its very loud, Pfc is at 360 which is a little low but not too bad. All output voltages are stable and the Tv works. Any ideas before I replace yet another one of these junks ?

[victor_cj]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Replace R805, R806, R807 1% tolerance and C890, C802 with other new.

[ReeceyBurger123]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Cheers will give it a blast.

[tom66]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

360 too low, needs to be 390V. The PFC will be dropping out under load and you will be getting peak currents flowing thru PFC inductor

[ReeceyBurger123]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Right replaced them parts no luck The Pfc is quite low, I have had others that do work at this voltage though, at 330v (on 240v ac) they fail Tom. I just can never solve this issue, any time I replace these boards is when the Pfc is bad.

[ReeceyBurger123]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Any suggestions ?

[ReeceyBurger123]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

I just dont get it, nothing tests out of whack all the little smd and larger resistors check good as well as the smaller ceramic caps (they normally fail S/C) any help is appreciated cheers !

[ReeceyBurger123]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Right off to bed now lol what I might do is remove the Pfc all together see how well it runs, it is possible by removing the mosfet, diode and controller, if not can get a board for £15

[flocko]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

I understand the need to repair, but looking at the list of parts that you have replaced and your time, and the fact that a replacement can be had for £15.you need to know when to stop trying to save this shit. Buy the the board for £15 fit it with nice new caps then send the set on its way, happy that you done your best. That could be your new years resolution ?

[rievax_60]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Q823 is a protection transistor. Is it being pulsed on?

[ReeceyBurger123]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Not too sure buddy will give it a shot.

[rievax_60]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Sometimes surface mount resistors can decrease in resistance in high voltage areas.

[ReeceyBurger123]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Decided to replace the board, simply not worth my time, something stupid is at fault here. Going to take my caps back and smash it up lol

[rievax_60]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Before you do. Take a reading of R926, R927, R928. Check them in circuit before any soldering is done. Look for a difference in reading. Are they surface mount?
I know it's a long shot.

[ReeceyBurger123]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Ok will do tomorrow buddy cheers.

[flocko]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Smash it up and move on, the satisfaction will help you to deal with not all ways being able to fix every thing ? just a little bit of Flocko therapy

[tom66]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

It's more fun to connect the bulk capacitor to 230V AC directly and stand back.

[ReeceyBurger123]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Replaced them and didnt work, now its going to suffer for wasting my time

[ReeceyBurger123]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Also got a few other Vestel boards that need a meeting with the hammer so they can join too.

[flocko]

Re: 17PW15-9 Horrible Buzz From Pfc Help ?

Be sure to put on your hard hat and safety goggles, these Vestal boards are known to put up a good fight, and do not like to get beat