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Sanyo DS-31650 shutdown - here we go again! :)

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BigMike

Jan 1, 1970
0
Hey guys, left a post about this Sanyo 31" DS31650 TV a while back, that had
a bad flyback and HOT. After replacing the set would turn on, but only for
about 3 seconds and then turnoff. Repeating pressing of the on switch will
get the tube to light up enough to show there is a raster, but no video.
Sound is fine. The customer decided to buy a new set right after this one
was brought in to me, and said he was in no hurry to fix it, so I set it
back while I had more pressing things to work on. Now I would like to get it
out of the shop. Before I order a schematic on this thing, I was wondering
if anybody had at least enough info on this chassis for me to take a crack
at fixing it without the schematic. The problem is the set won't stay on
long enough to do much. I'm sure the micro is tripping the set and shutting
it off, but I don't know if it might be the micro itself, which some have
claimed to replace and solve this problem, or whether the lack of a video
signal, is tripping the micro. If anybody has any info, schematic, or at
least the correct voltage points/waveforms to check that would cause the
micro to shut down, it would be appreciated. If not, I'll probably just
order the schematic and a new micro. I just hate rapping much money up in
this thing, since I doubt it will have all that much more life left in it.
Thanks!
 
D

David

Jan 1, 1970
0
If it is on 3 seconds or so, the micro is not seeing either the h-pulse or
the v-pulse to tell it that both circuits are running. Since the flyback
was back look for a line that goes to a zener diode that gets buffered and
goes to the micro for the h-sync pulse.

David
 
M

Mark D. Zacharias

Jan 1, 1970
0
I think I would check the 200 volt line. The timing sounds about right. Beam
current starts, gets excessive, shuts down.

Mark Z.
 
B

bigmike

Jan 1, 1970
0
David said:
If it is on 3 seconds or so, the micro is not seeing either the h-pulse or
the v-pulse to tell it that both circuits are running. Since the flyback
was back look for a line that goes to a zener diode that gets buffered and
goes to the micro for the h-sync pulse.

David

Thanks David, I'll give it a look. I have a raster for those 3 seconds,
just no video. However, I can see faint retrace lines in the raster, but
it's hard to tell if that might just be the screen control set too high,
since all I can see on the screen is the on-screen menu for those couple of
seconds. Anyway, I'll check it out. Thanks again.
 
B

bigmike

Jan 1, 1970
0
Mark D. Zacharias said:
I think I would check the 200 volt line. The timing sounds about right. Beam
current starts, gets excessive, shuts down.

Mark Z.

I'll give it a look. Thanks!
 
B

bigmike

Jan 1, 1970
0
Mark D. Zacharias said:
Yeah, now it REALLY sounds like the 200 volt line.

Mark Z.

Yeah, it does. I will try to track it down tomorrow and I'll let you know.
 
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