Prev: Technics RS-TR255 Cassette Decks
Next: how to hide a cell phone tower...
From: Steve Kraus on 17 Feb 2010 18:35
It's a KV27TS20 almost 19 years old. Don't worry...it's been superceded
with a nice Sony HD LCD TV. But I figured I would at least take a look
before tossing it. And fix it if it's something simple--even if it only
benefits the person picking up from curbside.

Symptoms: Totally dead. Does not respond to front panel or remote power
button. No relay clicks...no degauss buzz.

Some years back another similar looking Trinitron, only slightly younger,
died due to a failed regulator chip but you'd still hear the power relay
click and the degauss buzz if trying to power on after a long enough
interval. I fixed it with a new regulator chip.

That model had a separate power board but this one does not. Does the
"always on" power on this one come from the main regulator or someplace
else since that would seem to be the first place to look. I don't have a
schematic. I saw two fuses but they checked out ok.
From: David Farber on 17 Feb 2010 18:57
Steve Kraus wrote:
> It's a KV27TS20 almost 19 years old. Don't worry...it's been
> superceded with a nice Sony HD LCD TV. But I figured I would at
> least take a look before tossing it. And fix it if it's something
> simple--even if it only benefits the person picking up from curbside.
>
> Symptoms: Totally dead. Does not respond to front panel or remote
> power button. No relay clicks...no degauss buzz.
>
> Some years back another similar looking Trinitron, only slightly
> younger, died due to a failed regulator chip but you'd still hear the
> power relay click and the degauss buzz if trying to power on after a
> long enough interval. I fixed it with a new regulator chip.
>
> That model had a separate power board but this one does not. Does the
> "always on" power on this one come from the main regulator or
> someplace else since that would seem to be the first place to look.
> I don't have a schematic. I saw two fuses but they checked out ok.

Just follow the pc trace and see where the standby voltage is developed.
Shouldn't be too long a path. How much experience do you have repairing
tv's?

Good luck.
--
David Farber
David Farber's Service Center
L.A., CA


From: Adrian Glaubitz on 19 Feb 2010 03:49
Hi Steve,

Steve Kraus <screen(a)SPAMBLOCKfilmteknik.com> wrote:
> It's a KV27TS20 almost 19 years old. Don't worry...it's been
> superceded
> with a nice Sony HD LCD TV. But I figured I would at least take a
> look
> before tossing it. And fix it if it's something simple--even if it
> only
> benefits the person picking up from curbside.
>
> Symptoms: Totally dead. Does not respond to front panel or remote
> power
> button. No relay clicks...no degauss buzz.

first you should look up the chassis number of this set on the internet.
Once you it, check if you can find a list with common issues with this
set and their remedies. Since it is a Sony set, it should be easy to
find. At least, that's my experience with these. I don't have internet
access now and I'm writing this post offline with my handheld, otherwise
I'd look ot up for you. A very common website for such repair
information was http://eserviceinfo.com, I don't know though whether the
site is still up and running. I'd also check good old
http://repairfaq.org.

Good luck and greetings from Geneva/CERN,

Adrian
From: Steve Kraus on 21 Feb 2010 18:56
Thanks. I've tried to verify standby power and I do get 5V in once place
it's labeled. I figured if I can find something simple like a bad diode
I'd fix it but since I have no use for the set anymore I don't want to put
too much effort into it. I'll do a bit more searching before surrendering.

From: Steve Kraus on 23 Feb 2010 00:48
The plot thickens. I'm limited in what I can do with the main board hooked
up (about 20 connectors) and with it out of the set I'm not sure if my live
tests are valid. Anyway, I put it all back together, attempted power again
and still dead of course. But I left it plugged in. About 20 minutes
later I heard the power relay clicking and the LED flashing. I pushed the
power button a few times and the set came on.

I'm guessing the defective standby power may eventually charge a filter cap
to the point it can pull a relay in but in so doing the voltage droops
again unless one happens to be hitting the power button at just the right
moment when main power can take over. So it really must be something quite
simple. Or not. We shall see. I've not been able to trace things enough
to find fault but maybe I'll have better luck if I can track down a
schematic.

 |  Next  |  Last
Pages: 1 2
Prev: Technics RS-TR255 Cassette Decks
Next: how to hide a cell phone tower...