Sony 27" Trinitron Dead

S

Steve Kraus

Guest
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 Don't worry...it's been superceded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.
 
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superceded with a nice Sony HD LCD TV.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.
Click to expand...
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
 
Hi Steve,

Steve Kraus <screen@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superceded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.
Click to expand...
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
 
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.
 
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.
 
On Feb 18, 12:35 am, Steve Kraus <scr...@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.

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.
Click to expand...
Given the age involved, I'd just change the electrolytic caps on the
psu secondary and go over the soldering in the psu and line stage. The
symptoms suggest a cap or a cracked joint.
-B
 
Sony Trinitron KV27TS20

Good news. Never did find a schematic but Googling I found a mention of a
capacitor, C605. This is an electrolytic 22uF* rated at 250V. It didn't
look bad but unsoldering it it does look a little bulged at the bottom. I
didn't have anything like that laying around but figure a bigger cap in a
PS section might be worth trying I temp wired a 680uF* / 200V and with that
in the circuit the TV starts and behaves normally. So I need to find one
closer in value if not the exact replacement.

I measure 140V across it. It's there even with the set is off so obviously
standby related. I had no idea standby voltage was so high. I suppose it
could be from the wrong value; without a schematic I don't know if it would
do that. But that does indeed seem to be the source of the problem.

* microfarad of course. Can't get a mu on here.
 
If you were running Windows, you'd be able to get it from the Character Map
applet. And if you can also enter it directly by pressing ALT+0181.
 
Sylvia Else wrote:

* microfarad of course. Can't get a mu on here.

Here's one for future use: Îź
Click to expand...
Thanks Sylvia but that's not reproducing correctly here (running Xnews on
Windows XP). I tried using one and saw it wasn't going to work.
 
William Sommerwerck wrote:

If you were running Windows, you'd be able to get it from the
Character Map applet. And if you can also enter it directly by
pressing ALT+0181.
Click to expand...
Hmm...that one may work. ľ Thanks.

I'm not sure what one I tried (pasting in from elsewhere) but probably the
same thing Sylvia was suggesting. I don't know if others see that one
correctly but I didn't.
 
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