"b" <reverend_rog...@yahoo.com> wrote in message
news:e4159d34-fc6a-4427-800f-17350cf3a391_at_t20g2000yqa.googlegroups.com...
On Aug 28, 9:33 am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:
"b" <reverend_rog...@yahoo.com> wrote in message
news:8f75d703-8667-4259-8068-d91597e86867_at_q2g2000yqq.googlegroups.com....
This 14" 11AK36-A8 tv apparently 'just went off.' there was evidence
of a short near the mains inlet, on the print side of the pcb -
probably a strand of wire or blob of solder from the time of
manufcture had been the cause. checked rectifier, removed PTC in case,
replaced fuse. Set dead. 0v at psu o/ps.
checked the obvious in psu primary, no shorted diodes or open
resistors. Removed secondary diodes including HT line.
schematics here (5m). Psu is on page 24.:
http://www.fileden.com/files/2007/6/4/1143893//11AK36
FULL.pdf
...not identical but the main aspects are the same.
300v present across mains capacitor, and at R821 (safety) and
collector of Q801.
25v present at c811, suggesting the uPc of the PSU has power.
I don't know where to look now. My next step would be to change the
uPc UC3843, but I don't think I've ever seen a case where the chip
went on its own...
I should probably have tossed this aside by now but I'm just keen to
satisfy my curiosity. So I'm all ears.
cheers,
B.
The link doesn't seem to get you direct to the schematic. Seems to want a
login from the home page ?
As for '3843s, I have had them go faulty on their own on other Vestel
PSUs,
but I agree, it's rare. Have you ESR checked any small primary-side
electrolytics ? Is there anywhere else I can get a squint at the schems,
or
can you mail the pdf to me direct ? I do quite a lot of switchers, and
used
to do a lot of Vestels from bigger LCD TVs, so I might be able to offer
an
insight or two ...
Arfa
thanks. try this link:
http://www.fileden.com/files/2007/6/4/1143893/11AK36%20FULL.pdf
I got this from eserviceinfo originally, I think.
Re: electrolytics, besides the mains filter cap I think there's only
the one I mentioned (c811)
cheers
Ben
On some of the Vestel supplies that I've worked on, I have had problems with
the high voltage polyester caps going open. That 47nF 630v one, C812, would
be a prime one to check, particularly if it's a bright blue 'boxy' one,
rather than a brown epoxy coated type. I'll have a bit closer look tomorrow.
Arfa
