J
JURB6006
That comment was made by a tech named Art with whom I used to work. He was
joking at the time, but it actually happened to me. I had an XBR RPTV and had
fixed the vertical yet the set would still shutdown. Through the chassis went
the wire to the subwoofer and the set wouldn't run with it unplugged.
This RCA was a must do, even if it took all day. They had their hotshot look at
it and this guy has fixed a couple things that had me stumped. I caught this
one.
I posted about it, but it was plenty wierd. Nailed it today.
Originally the set came in with a shorted HOT, but we were at a loss to explain
why. Replaced it, geometry perfect, no bulging caps, however the standby B+ was
just a bit high. Did the caps in the SMPS. I figured maybe the HOT had a bad
day, played the set the rest of the day and pronounced it cured. It was not.
About half the time from a cold start it would come up with no audio and the
display shifted left (not right). What's more it wouldn't act up when the
chassis was pulled upright for testing. This wasn't apparent in the beginning.
I'm back to theory, print, scope and showing my (_|_).
Turned out to be the 503Khz crystal off the jungle IC. The way it happened is
that the crystal finally went, the mechanism by which it caused this symptom
follows.
The crystal was somehow damaged and it was "weak", thus the Vcc to the EPROM
was too late because while not scan derived, requires scan for the 5V run
regulator to function.
Actually the way I found it is that it finally quit completely while the other
guy was working on it. I'm suprised that he changed the jungle IC before the
crystal actually, but nobody's perfect.
Moral of the story: don't forget the crystal for the horizontal. If that thing
stops oscillating while the HOT is turned on, it will fail in as little as
1/15,734th of a second. Collector current ramps up higher and when the field
collapses in the driver transformer the spike from the flyback destroys the
HOT. It doesn't even heat up.
Decieving symptoms, psycopathic symcures or wacky wetdreams, call it what you
want, but I post it in the hope it'll help someone in our war with the
manufacturers. I'm happy to be responsible for one more unsold new TV.
JURB
joking at the time, but it actually happened to me. I had an XBR RPTV and had
fixed the vertical yet the set would still shutdown. Through the chassis went
the wire to the subwoofer and the set wouldn't run with it unplugged.
This RCA was a must do, even if it took all day. They had their hotshot look at
it and this guy has fixed a couple things that had me stumped. I caught this
one.
I posted about it, but it was plenty wierd. Nailed it today.
Originally the set came in with a shorted HOT, but we were at a loss to explain
why. Replaced it, geometry perfect, no bulging caps, however the standby B+ was
just a bit high. Did the caps in the SMPS. I figured maybe the HOT had a bad
day, played the set the rest of the day and pronounced it cured. It was not.
About half the time from a cold start it would come up with no audio and the
display shifted left (not right). What's more it wouldn't act up when the
chassis was pulled upright for testing. This wasn't apparent in the beginning.
I'm back to theory, print, scope and showing my (_|_).
Turned out to be the 503Khz crystal off the jungle IC. The way it happened is
that the crystal finally went, the mechanism by which it caused this symptom
follows.
The crystal was somehow damaged and it was "weak", thus the Vcc to the EPROM
was too late because while not scan derived, requires scan for the 5V run
regulator to function.
Actually the way I found it is that it finally quit completely while the other
guy was working on it. I'm suprised that he changed the jungle IC before the
crystal actually, but nobody's perfect.
Moral of the story: don't forget the crystal for the horizontal. If that thing
stops oscillating while the HOT is turned on, it will fail in as little as
1/15,734th of a second. Collector current ramps up higher and when the field
collapses in the driver transformer the spike from the flyback destroys the
HOT. It doesn't even heat up.
Decieving symptoms, psycopathic symcures or wacky wetdreams, call it what you
want, but I post it in the hope it'll help someone in our war with the
manufacturers. I'm happy to be responsible for one more unsold new TV.
JURB
