VESTEL 17PW15-8, VERY LOUD BUZZ.

[JAYROD]

 
Hi. I have a bush lcd tv that is producing a loud buzz from the power supply [ it`s ok in standby ].
The problem seems to be centered around the PFC circuitry causing transformer TR806 to buzz.
There is a unusualy large amount of ripple on smoothing cap c819, 150uf 450v.,which i have checked and found to measure slightly low at 135uf . I have repaced it with a 220uf which is the value usually used on these boards. This has stopped the board buzzing but i think that this may be just masking the real cause.
Prior to replacing c819 i changed IC802 but no improvement.
Had the same problem with one of these boards, [17pw15-8] about 12 months ago on which c819 was ok.
On that occasion the fault was intermitent. I spent a lot of time replacing most of the components connected with IC802 circuitry to no avail. Ended up replacing the board.
Please has any one got an answer to this problem.

     Thanks, phil.   :wallbash:

[UGM-Lite]

Hi,

I have a Vistron 26" set using a 17PW15-8 that makes a very loud buzz around the PFC transformer TR806. Nice and quite in standby. The buzzing stops when connected to a variac with output of the variac at 231 Volts.

Anyone got the answer ? 

[dougc]

Have you tried replacing the transformer? Just a thought, Doug

[sparky]

hi
might be the 2x 15nf blue caps
dave

[Turnip]

Hi Sparky,

Thought Jayrod had it well sorted with that main cap. If cap left original the PFC section will probably pop making for a decent repair bill - Chris.

[sparky]

hi
chris he sorted it by changing panel?
dave

[Turnip]

Hi Sparky,

Well observed - Jayrod's was an awful long post and I missed the end bit - confess never had O/C 15nf caps causing PFC buzz - usually no main secondary outputs and easy pounds earned - Chris.

[UGM-Lite]

Thanks Guys for the tips. Already tryed your suggestions sadly no luck.

I'm guessing it is a common problem I have 4 of these PSU removed from sets with faulty screens that were brand new in 2006. I have kept these PSU now for 5 years and have only just fitted them in sets, and they have turned out to be duff from new. Oh well...

[Turnip]

Hi UGM light,

Hang in there - several Quuq folks have had vast Vestel experience, just waiting for them to get their thoughts together - if at all possible.

In my day trouble was with French 'EMO' televisions, where when we checked shematics, we agreed they couldn't possibly work - they didn't - well, for long - Chris