Shorted HOT's in newer TV's

[radiotvnut]

Over the years, I've seen many newer solid state TV's with shorted horizontal output transistors. Knowing that they often have help shorting, I usually check things before installing a new HOT. Things such as proper operation of the power supply, bad caps, bad solder connections, and testing the flyback with a ringer. After doing all this, I'll power up the set with a good HOT. Sometimes, I'll get lucky and the set will work. Other times, the HOT will either blow instantly or it will overheat and short again in a brief time period.

I know some of you have been in the repair business for a long time and I'd like to know is there any other way I can possibly keep the new HOT from shorting if there's still a fault with the chassis? Several years ago, a friend had about $10K worth of Sencore equipment and one of those pieces of equipment would perform a "load test" on the entire horizontal sweep circuit; but, I don't have the luxery of owning such expensive equipment. The only thing I have is a late '70's era Sencore flyback and yoke ringer and, in the newer SS sets, the flyback must be taken out of circuit for an accurate reading. And, this is one area where tubes are more forgiving. If there's a problem in a tube HOT circuit, one generally has a little warning. In a solid state set, the HOT can be destroyed instantly. Right now, I'm working on a 32" 2002 Toshiba that uses an oddball HOT that's $10 plus shipping. I resoldered a bunch of questionable connections, replaced a questionable electrolytic cap in the power supply, checked the 130V B+, and performed a ring test on the flyback. Everything seems to be OK; but, I'd sure hate for the new transistor to go up in smoke as soon as I push the power button. $10+shipping for transistors gets expensive at that rate.

As far as older SS sets from the '70's, I don't recall seeing nearly as many from that era with shorted HOT's. And, it was often easy to find the problem on the ones with shorted HOT's. And, those older '70's era sets didn't seem to run as hot. I have a Zenith CCII and a Sylvania superset from the '70's. Both use a metal cased TO-3 style HOT mounted on a decent heatsink. These sets can run for hours and the heatsink will be only slightly warm. Now, take a later model Chinese made CRT set and the HOT heatsink will be very hot after 30 minutes of operation. In the newer sets, they must be running these parts right up to their maximum design limits. That could explain why they don't last as long.