Sony KV-2781R, HOT replaced, no video, sound ok

[Diaspar Lynn]

Hi,

I'm working on a Sony KV-2781R. The HOT was shorted and the fuse F1601
opened. I replaced them; I also replaced C578 and Q501 by the equivalent. I
measure voltage below the nominal on TP97 (90V instead of 135) and on TP95D
(7V instead of 9V).

The TV turned on, the audio output is OK but it have no video; however, a
blurry and moving OSD appears on a black screen. The same happen using the
external video input.

Thanks in advance for any help.

L.G.
Toronto

 

[Jerry G.]

This is a general suggestion. You may have an output voltage missing from
the secondary side of the flyback circuit that feeds the video amp section.
Some of the Sony sets use a supply from the flyback secondary to operate
some of the video amp sections.

You can use a scope to verify the video amp performance to start with.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
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"Diaspar Lynn" <diasparlynn@yahoo.com.ar> wrote in message
news:zNimb.25341$XO.1292278@news20.bellglobal.com...
Hi,

I'm working on a Sony KV-2781R. The HOT was shorted and the fuse F1601
opened. I replaced them; I also replaced C578 and Q501 by the equivalent. I
measure voltage below the nominal on TP97 (90V instead of 135) and on TP95D
(7V instead of 9V).

The TV turned on, the audio output is OK but it have no video; however, a
blurry and moving OSD appears on a black screen. The same happen using the
external video input.

Thanks in advance for any help.

L.G.
Toronto

 

[Andy Cuffe]

Diaspar Lynn wrote:

Hi,

I'm working on a Sony KV-2781R. The HOT was shorted and the fuse F1601
opened. I replaced them; I also replaced C578 and Q501 by the equivalent. I
measure voltage below the nominal on TP97 (90V instead of 135) and on TP95D
(7V instead of 9V).

The TV turned on, the audio output is OK but it have no video; however, a
blurry and moving OSD appears on a black screen. The same happen using the
external video input.

Thanks in advance for any help.

L.G.
Toronto

The 135v source comes from the low voltage power supply. Every time
I've seen a shorted HOT in one of these, it also took out the low
voltage regulator (STR3135 I think). Replace the small electrolytic in
the horizontal drive circuit if that wasn't C578. I think it's near the
vertical output heat sink. Also check the soldering on the horizontal
drive transfomer.
--
Andy Cuffe
baltimora@psu.edu