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Post by hellcat on Mar 21, 2019 16:01:26 GMT -5
My Mark lll has a good dead key (4 watts) and very very weak audio. I have swapped out all of the tubes with new ones and still the same result. I’ve even tried 3 different microphones. Something I’ve noticed when pushing the spot button there is no tone, just a hissing noise. I’m thinking my modulation transformer has gone bad. Any suggestions?
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Post by 2600 on Mar 21, 2019 21:14:33 GMT -5
Failed capacitors including C47b, C54. Failed resistors including R37, R39 R47 and R49. Most especially a burned R51 can do this. If this resistor is burned, that points to a failing mode-selector switch. This one should have the color bands orange-orange-red, followed by silver or gold. If the color bands are darkened, or the middle one turned brown, that's a bad sign. Not the whole list of possibilities, only the most-common ones. 73
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Post by narfedwards2 on Mar 22, 2019 10:27:53 GMT -5
I had a 0.47 yellow cap off the 12ax7 where the spot switch splits off go open on me...need a signal tracer start at mic input work yer way down
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Post by hellcat on Mar 23, 2019 3:13:27 GMT -5
Thanks, I will check all of these
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