Sony KV27TS29 Power supply and SLV555UC Power supply

[allt...@ix.netcom.com]

I've now got 2 KV27ts29's with the same problem. The switching
transistors in the power supply are shorted and a fusible resistor burns
out. The two transistors are both 2SC4834's.

Replaced the bad transistor with original numbers but not from Sony.
Also replaced the resistors that were open. Set would work for short
time, then BANG, the parts would destroy themselves again.

I fixed one just like this before, and the customer still has it and it
works fine for months now.

Any clues here.

Also, I have 2 SLV555UC vcrs with a shorted zener diode in the power
supply. I replaced one and the unit returned about a month later with
same part bad. Replaced the filter cap 1500mfd 25vdc in parallel with
it and same result. Again, not Sony originals, but equivelants.

Zener is a 12V type. Location, if memory serves, is D206.

Thank you,

Wayne
______________________________________
All-Tronics

[Francis Gagnon]

Sorry for the TV, I cannot help you.

For your SLV-555, the zener diode that usually blows up is a 16V glass type.
When you replace this diode, you ABSOLUTELY have to replace the two
capacitors on the primary side of the power supply. It's a 160V 1uF and a
4.7 or a 47uF 50V. (not sure of the last value..) Try to replace them with a
200V and a 63V, wich should resolve the long terme problem.

Good luck
________________________________________________________
Francis VE2FGS
SONY tech. support
sony...@videotron.ca

allt...@ix.netcom.com a écrit dans le message
<34DF3C...@ix.netcom.com>...

[Tony]

As for the TV:
When Q601 and Q602 are replaced, sony states that VDR601, VDR602 and VDR603
should be replaced too. Also check the values of R607, R651, R652, R644,
R684 and R636. Now after replacing all of the bad parts, run the set and
see if Q601 and Q602 are running excessively warm. If they are, scope the
primary of T601. It should be a ultra clean square wave. If it has any
distortion, replace T601.
As for the VCR:
Whenever I replace the zener, I replace C109... I have found it to have high
esr causing the zener to short.
Hope all of this helps.
--
Tony
Over 30,000 repair tips!
Free Shipping
http://www.catalog.com/ame/

allt...@ix.netcom.com wrote in message <34DF3C...@ix.netcom.com>...

[Greg M]

> Also, I have 2 SLV555UC vcrs with a shorted zener diode in the power
> supply. I replaced one and the unit returned about a month later with
>
> same part bad. Replaced the filter cap 1500mfd 25vdc in parallel with
>
> it and same result. Again, not Sony originals, but equivelants.
>

There are 2 electrolytics on the primary side . Replace them both . When
these go bad the cause the SMPS to increase the output of the secndary.
Causing too high an ouput and the zener breaks down .

Greg

[tvman]

allt...@ix.netcom.com wrote:
>
> I've now got 2 KV27ts29's with the same problem. The switching
> transistors in the power supply are shorted and a fusible resistor burns
> out. The two transistors are both 2SC4834's.
>
> Replaced the bad transistor with original numbers but not from Sony.
> Also replaced the resistors that were open. Set would work for short
> time, then BANG, the parts would destroy themselves again.
>
> I fixed one just like this before, and the customer still has it and it
> works fine for months now.
>
> Any clues here.
>

> Also, I have 2 SLV555UC vcrs with a shorted zener diode in the power
> supply. I replaced one and the unit returned about a month later with
> same part bad. Replaced the filter cap 1500mfd 25vdc in parallel with
> it and same result. Again, not Sony originals, but equivelants.
>

> Zener is a 12V type. Location, if memory serves, is D206.
>
> Thank you,
>
> Wayne
> ______________________________________
> All-Tronics

I had the same problem. I inserted .15 @ 5 watt resistor in series with
the emitter of each transistor and cured the problem. I have done this
quite often without a sigle come-back. I have some repaired over a year
with out a problem.

tvman@flashnet

[Binh Tran]

What is the problem? I cannot find the first post of the thread!

I have a 26" SONY, about 10 years old, can't remember model number.
When I try to power on, I hear a few clicks, but will not powered on.
Any one have any clue? it sound like all the SONY TV having the same
power supply problem.
Thanks.