Riddled TV Repair Forum

Steve · Guest

dead, I replaced the 2A fuse powering the 5v line. Of coarse no 5V means no switch detection or microprocessor power. I was happy to see a picture then I saw the intermittent flicker that was clearly loss of horizontal drive. I suspected the flyback arcing immediately as the Flyback was getting warm to the touch. So I replaced with an ASTI 95-4732. Same issue persists. The drive transformer circuit is OK, no cold solder. Any ideas? Experience with this exact problem/symptom? It is an older set chassis 9-1408. Has anyone ever seen the horiz. output transistor cause intermittent deflection on its own.

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David · Guest

Yoke?

Bryan · Guest

Not seen that problem on a C-10 series set but it IS a common failure on the
46DT series educational sets of the same era. The yolk shorts takes out the
H.O.T. and sometimes cooks the fly. The unfortunate dilemma on those sets is
the CRT and Yolk are bonded and being a Data grade CRT it can get quite
spendy.

Jim · Guest

replace c2212 .I think it is located off pin 6 of the micro ic .It should be
22 mfd

Terry · Guest

David, I have used another yoke from another chassis with an impedance
close to the original and using test leads wired in the horiz. yoke circuit
just to see if the HV would come up and stay. If yes, bad yoke like John
said, if not then some other component loading down that circuit.

Terry

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David · Guest

Terry, so the results were the same with the closely matched yoke? I'm
assuming you were still experiencing the same intermittent flicker. What
else in the horizontal circuit could cause this? Hmmm...maybe an
intermittent horizontal drive transformer. Are you sure the flicker is in
the horizontal and not the vertical circuitry? Horizontal would cause an
east to west collapse and vertical north to south, you know this already but
I had to ask. Are you able to scope this intermittent? What do you see on
the scope? I hate intermittent problems :-(

Tom · Guest

Check/replace 100m/25v filter in regulator circuit and the filter for the
power supply to the horizontal section of the video/sweep IC.

be sure and check all the caps near the jungle chip. Look for a 22mf
or a 2.2 mf. Hope this helps.