Help Please: Sudden Video Failure with Sony SLV 770HF VCR

[Ron Kalil]

I have owned a Sony SLV 770HF VCR for several years, but have used it only
infrequently. When I have used it, it has alaways worked well. Now, with no
prior warning, the machine appears to have failed. Upon turning it on
everything seems normal. When playing back a tape, the first few minutes also
seem normal, but then scattered horizontal interference begins to intrude as if
the tape was not making good contact with the head. The interference is
followed at an interval that varies from 5 to 15 minutes by loss of the chroma
signal. The gray scale in the resulting monochrome image then slowly compresses
until only white outlines on a black background are visible. Within 5-10
additional minutes, the high contrats image disappears entirely and cannot be
recovered. If the machine is turned off for at least 30 minutes, the entire
sequence repeats.
The symptoms suggest a time/temperature dependent failure, but I am puzzled by
why a temporary recovery is possible when the machine is turned off.
If anyone has repair experience with a Sony VCR with a similar progression:
flutter, lack of chroma, lack of gray scale, lack of image, I would be very
grateful for your advice. I would like to keep the machine and should be able
to repair it myself, but I need some help in diagnosing the source of the
problem.
Thanks very much.
Sincerely,
Ron

 

[bigmike]

I have owned a Sony SLV 770HF VCR for several years, but have used it only
infrequently. When I have used it, it has alaways worked well. Now, with no
prior warning, the machine appears to have failed. Upon turning it on
everything seems normal. When playing back a tape, the first few minutes also
seem normal, but then scattered horizontal interference begins to intrude as if
the tape was not making good contact with the head. The interference is
followed at an interval that varies from 5 to 15 minutes by loss of the chroma
signal. The gray scale in the resulting monochrome image then slowly compresses
until only white outlines on a black background are visible. Within 5-10
additional minutes, the high contrats image disappears entirely and cannot be
recovered. If the machine is turned off for at least 30 minutes, the entire
sequence repeats.
The symptoms suggest a time/temperature dependent failure, but I am puzzled by
why a temporary recovery is possible when the machine is turned off.
If anyone has repair experience with a Sony VCR with a similar progression:
flutter, lack of chroma, lack of gray scale, lack of image, I would be very
grateful for your advice. I would like to keep the machine and should be able
to repair it myself, but I need some help in diagnosing the source of the
problem.
Thanks very much.
Sincerely,
Ron

Check head preamp board: Ic1 for a leaky 2.2uf/35 Smd Cap. Also, look for
bad solder joints on the board, a common problem.