More Sony KV-27TS29 Problems

[Chris F.]

I shouldn't have tried to fix this at the end of the day, when I was very
tired........
As suggested, I found cold solder joints around the horizontal driver
transformer and fixed them. The company I ordered the replacement parts from
didn't tell me the HOT I ordered was out of stock, so I ended up having to
sub with an ECG 2302 - which was probably not a match. I ordered a
replacment flyback anyway just for good measure, and installed it. The set
powered for a few seconds, then the HOT shorted and blew the crap out of the
switching power supply. Before I can even begin to sort out what happened, I
need one piece of important info:
Value of R656 (on SMPS). This was burned beyond recognition. Some arcing
occured in the area also taking out a diode or two, but I think the numbers
are still readable on those. I need to get the SMPS going before I can
troubleshoot anything else.
Thanks so much for your help.

 

[Don]

I shouldn't have tried to fix this at the end of the day, when I was very
tired........

Be thankful you're not a SURGEON! :>

As suggested, I found cold solder joints around the horizontal driver
transformer and fixed them. The company I ordered the replacement parts from
didn't tell me the HOT I ordered was out of stock, so I ended up having to
sub with an ECG 2302 - which was probably not a match. I ordered a
replacment flyback anyway just for good measure, and installed it. The set
powered for a few seconds, then the HOT shorted and blew the crap out of the
switching power supply. Before I can even begin to sort out what happened, I
need one piece of important info:
Value of R656 (on SMPS). This was burned beyond recognition. Some

Parts list shows that (on the *D* board?) as P/N 1-249-381-11,
1 (!) ohm, 5% 1/4W. But, I haven't found it on the schematic yet
to verify that these values "make sense". Any hints as to what
it is *electrically* adjacent to?

arcing
occured in the area also taking out a diode or two, but I think the numbers
are still readable on those. I need to get the SMPS going before I can
troubleshoot anything else.
Thanks so much for your help.

Good luck!
--don

 

[Chris F.]

Parts list shows that (on the *D* board?) as P/N 1-249-381-11,
1 (!) ohm, 5% 1/4W. But, I haven't found it on the schematic yet
to verify that these values "make sense". Any hints as to what
it is *electrically* adjacent to?

S'funny, the resistor was smaller than your average 1/4 watt job. I thought
it was 1/8th. Maybe the parts list specifies a 1/4 watt because it's a
superior replacement.
It was located among some red mylar capacitors and other resistors. At least
one mylar cap was blown apart, but the number was still readable. I'll have
to go through the SMPS piece by piece to make sure there aren't any other
bad components, before I power up again. Also, I don't have any proper
replacements for the two switching transistors so I will fit in some (much
higher-rated) NTE 2308's instead. I intend to keep this set for my own use
if I get it going, so at least if I make some strange transistor subs I
won't have to worry about it blowing up on a customer.
I will try that resistor and let you know how I make out.
Thanks again.

 

[Don]

S'funny, the resistor was smaller than your average 1/4 watt job. I thought
it was 1/8th. Maybe the parts list specifies a 1/4 watt because it's a
superior replacement.
It was located among some red mylar capacitors and other resistors. At

least

Found it. It and C612 (0.22) sit in series between the base and emitter
of Q602. Make sure D605 hasn't opened (it sits across Q602 B-E junction
and clamps Vbe when the base drive swings negative). C611, R653 and
D603 do the same for Q601 (symmetry). Can't hurt to poke around
there as well!

one mylar cap was blown apart, but the number was still readable. I'll have
to go through the SMPS piece by piece to make sure there aren't any other
bad components, before I power up again. Also, I don't have any proper
replacements for the two switching transistors so I will fit in some (much
higher-rated) NTE 2308's instead. I intend to keep this set for my own use

electronix.com offers a kit for *your* set (Q601, Q602 , HOT and
fusible resistor) for ~$7. May be worth the few dollars. (My KV32S22
aparently uses a different HOT... haven't had time to look up the
datasheets)

if I get it going, so at least if I make some strange transistor subs I
won't have to worry about it blowing up on a customer.
I will try that resistor and let you know how I make out.
Thanks again.

HTH,
--don

 

[Chris F.]

I got the SMPS going, but haven't had much luck otherwise. TV powers, but HV
is low (14kv, even though the B+ is 150V or so) and the HOT quickly
overheats - blows if I leave the set on for more than 10 seconds at a time.
I noted that when I run the set with the yoke disconnected, the HOT heats up
even faster. The HOT isn't the exact one, but the replacement is rated
equal or greater than the original. I've tried several different HOT's and
had the same result. I've also ruled out the flyback as a suspect at this
point. I suspect some kind of problem in the horizontal drive circuits.
Any ideas? A scan of the horizontal output area of the schematic would be
helpful, if anyone could find the time to do that for me.
Thanks again.

 

[Leonard Caillouet]

Why have you ruled out the FBT?

What does the HOT collector waveform look like when you fire it? Is it
normal? 150v for the B+ seems high. Shouldn't it be around 135v?

Leonard

 

[Chris F.]

You won't believe what was the cause of the problem mentioned in my
previous post: the HOT was installed backwards. Yes, backwards, on the wrong
side of the heatsink. It wasn't entirely my fault; the "tech" I bought this
set from had removed the original HOT, and put the screw back in the
heatsink on the opposing side. There are no "B-C-E" markings on the board
either. I finally clued in when I realized that the base drive signal was
going to the emitter of the transistor.......
The end result is a good-working set. I may even keep it for my own use,
if I like it better than my flat 27" RCA (CTC-169).
Thanks to all for the advice.

 

[john]

That I dont believe ..!!!

kip

Pretty tough on a 169
Backwards on the correct side Yes but not on the other side.

You won't believe what was the cause of the problem mentioned in my
previous post: the HOT was installed backwards. Yes, backwards, on the wrong
side of the heatsink.