TRRI comes in for "dreadful screeching noise". It makes no such noise in my shop. Guy tells me he changed all the tubes, and it still did it, so he brought it to me. I did find a white capped new reverb driver tube, but still no screechng. Then I noticed the two 1 watt 470R screen resistors on the right side were toast. I replaced them with 2 watts, and can find nothing else wrong.
So what puzzles me is, why two screen resistors? If one power tube went bad and took out it's screen resistor, why did they both go?
I figure one 6L6 was failing and roasting it's screen resistor, so he changed the tubes, and maybe the roasted resistor had it's last death throes while the new tubes were just installed, and had finally given up fully by the time it got to me. Becayse he will want to know why the noise happened before and after he changed to new tubes.
I checked the bias voltages to all pin 5's whilst wiggling and prodding wires and the two 220K resistors looking for a possible lost connection, but it all seems real solid.
https://www.ampwares.com/schematics/...verb_ab763.pdf
So what puzzles me is, why two screen resistors? If one power tube went bad and took out it's screen resistor, why did they both go?
I figure one 6L6 was failing and roasting it's screen resistor, so he changed the tubes, and maybe the roasted resistor had it's last death throes while the new tubes were just installed, and had finally given up fully by the time it got to me. Becayse he will want to know why the noise happened before and after he changed to new tubes.
I checked the bias voltages to all pin 5's whilst wiggling and prodding wires and the two 220K resistors looking for a possible lost connection, but it all seems real solid.
https://www.ampwares.com/schematics/...verb_ab763.pdf
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