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Old 07-05-2017, 03:04 PM
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Findm-Keepm Findm-Keepm is offline
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Join Date: Jun 2007
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Quote:
Originally Posted by radiotvnut View Post
Over the years, I've had several 13" and 17" BC chassis sets and most of them had a bad flyback. In my area, we have very hot and humid Summers and I think this is why so many flybacks and triplers failed in sets around here. I recall picking up one 17" BC chassis TV off the street and after replacing a bad power switch, it came to life - for about 15 minutes. I was test running it; and, all of a sudden, the picture got darker, fell out of sync, pulled in on the sides, and BAM - the flyback went up in smoke and stunk up my shop. When it went, it also took the HOT, voltage regulator, and both fuses with it.
Classic solder on the horizontal drive transformer gripe. It'd eat a flyback in an instant. The set heats up, warps the board just so, and boom - no/reduced drive, and the horiz output transistor goes into near or 100% conduction, eating the primary coil on the fly. Overcurrent protection was nil, or a small (fusible) resistor of a half-ohm or so in the B+ to the transistor collector - the fly would go, and the resistor was fine.
It was a must on these sets to resolder (with lead/tin solder) the horizontal drive transformer, the HOT connections, and check the ESR of the caps on the scan derived side - the ripple current would overheat the fly as well...

Funny thing - RCA's 2005-ish M134C chassis had the same problems....seems they never learn....
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USN RET (Avionics / Cal)
CET- Consumer Repair and Avionics ('88)
"Capacitor Cosmetologist since '79"

When fuses go to work, they quit!
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