Freeze spray to the rescue. In a pinch you can use a can of compressed "air" like you would get at a stationary store. Most of those don't actually have air in them, they use refrigerant. Just hold the can upside down when spraying and it comes out as a liquid.
The fact that the beta of a transistor increases with temperature is well known to analog guys. It's what leads to thermal runaway in power amplifiers if you're not careful.
I would try and isolate and test each one of those transistors on their respective bands, before taking the board out; make sure you've found the right one(s). Thanks to that viewer(s) recommendations/insight!
That power amplifier looks like the one in the Kenwood TS-930 and it has intermittent no power problems and its bad connections on the circuit board-the board has feedthroughs that can cause problems
Get a McDonalds drink straw. Place it over the component to be frozen and squirt freeze-it down the straw. There is less "collateral" cooling. You can also use Computer duster spray but invert the can to get the freeze.
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Freeze spray to the rescue. In a pinch you can use a can of compressed "air" like you would get at a stationary store. Most of those don't actually have air in them, they use refrigerant. Just hold the can upside down when spraying and it comes out as a liquid.
The fact that the beta of a transistor increases with temperature is well known to analog guys. It's what leads to thermal runaway in power amplifiers if you're not careful.
Thanks to genius Mike! 😉
I wet the end of a Q-tip with the freeze spray to easily isolate a single component. de WG2E
Interesting. I have never heard of this but glad you found the problem.
BTW, the 2sc460 is pretty close (at a high level) to a 2N3904 that you could swap it and see if things stabilize.
I would try and isolate and test each one of those transistors on their respective bands, before taking the board out; make sure you've found the right one(s). Thanks to that viewer(s) recommendations/insight!
That power amplifier looks like the one in the Kenwood TS-930 and it has intermittent no power problems and its bad connections on the circuit board-the board has feedthroughs that can cause problems
Get a McDonalds drink straw. Place it over the component to be frozen and squirt freeze-it down the straw. There is less "collateral" cooling. You can also use Computer duster spray but invert the can to get the freeze.
Playing cat and mouse with those pesky little semiconductor buggers? Nice method.