Quote:
Originally Posted by Electronic M
Back in the day TV techs used to find thermally dependent faults with freeze spray. Get some canned air or that old radio shack tuner cleaner that is basically oil that comes out of the can frozen and with the set on and the chassis jigged so you can access everything in the circuit with it running hit every component in the offending circuit a few at a time once warm and see which component when chilled puts it back to the cold operation state, once you find a region of the circuit that effects it narrow your chilling until you isolate the exact part that's causing it.
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About thermal related issues, like the original in thread (seems to be tube related as the last timmy's posting), I have sucessfully finally solved the the mystery of my Telefunken TV, using a electrical cleaner spray. I discovered (well, remembered... thanks to Electronic_M tip) this spray cooled surfaces, so I can try on this TV (when finally I had the time). One vertical output transistor reacted to it (thermally)(a TIP31), and, I discovered some hygroscopic resistor in series with the vertical centering control, and/or in the feedback arm... exactly what one I don't had the patience to discover; I changed all ones at the smalles area I can apply the spray (only 4 resistors). Super stable after this.