Hi,

Hello,

I have a 16-year old SONY KV-X2531D (AE1C-Chassis) set which has been
repaired several
times already but still doing tough so far. Now it has started to drop
green-color
intermittantly meaning that it comes back after certain circumstances. I
have made
the following observations/measurements so far:

Green drops in normal reception-mode giving the picture a red tint but
picture visible, turning set
into StandBy and turning it on again will sometimes bring the green back
but mostly screen will just remain black (slight raster visible though).
What really
puzzles me is that activating videotext works (i.e. I get the
text-picture) with green-color missing. But normal reception or OSD
(green) does not show up
(I'd expect the video also to appear with green missing, but video is just
black
and videotext with green missing). I cannot influence the color-dropping
mechanically
which would probably unveal dry solder joints.

Anyway, I checked the voltages on the CRT-neck board:

- 12V from video-board is okay
- R,G,B from video-board measure around 12V AC
- R,G,B directly on CRT-neck measure 280 (R), 350 (B), 480(G) AC-V

So has anyone any suggestions ? I suppose this must originate somewhere on
the video-board, since all video generated by the set itself works (except
for green missing thus no OSD/videotext with no green) but external
sources (tuner/AV) do not.


Hooray !

With the help of the Service Manual with schematics for AE1C, my
DMM/Scope and freeze spray I finally found the one to blame .
I traced the luma-signal up to the jungle-IC (TDA-4580/IC301)
and up it to the latter it was okay. But the RGB-output of it
was not ok. So I gave the jungle-IC a breathe of freeze spray
with the set being on and a video signal connected and voila -
the picture turned back to perfectly normal. After short
period it would turn black again, so the jungle-IC is bad.
I could reproduce this behavior any time and I also found
some other posts with "NO PIC-REPLACE TDA4580", so I'll
give it a try.

I already bought replacement online and will have the IC (28DIL)
be replaced by an professional technican at my work in university
(I simply pulled out the B1 video-board), as he has a profesional
rework station (as opposed to my soldering iron bought at Home
Improvement ). I'm looking forward, whether this will fix it.
I will post the results anyway.

Regards,

Adrian