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PostPosted: Sat Jan 23, 2021 6:50 pm 
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Joined: Thu Dec 03, 2020 11:11 am
Posts: 5
Finished up my TripTop build today. Found a few interesting voltage readings while doing the final check. Any help or advice would be fantastic

I tripled checked all my soldering points, resistor values and capacitor impedance. All are good and correct. Cathode based biasing is dead on at 39vdc

B+ Voltage is 419. Mains is 117v

-All of my above 100v test points are reading 20v lower than the target except for:
-Voltage on pin 2 and 5 on V2 are around 30v higher than the target voltage on the 6550 sheet. Does not matter if in fixed or cathode based
-I cannot get the bias adjustment to work properly. It will not allow me to drop below 70ma fully counter clockwise. I have the 15k resistor instead of the 22k according to the update. I also have positive voltage at pin #1 on both power amp tubes I am using KT120 tubes


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PostPosted: Thu Jan 28, 2021 11:54 pm 
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Joined: Thu Dec 03, 2020 11:11 am
Posts: 5
Update:

Amp is fixed! Lots of great testing info from Stephen.

Long story short, my bias pot was bad. As I was investigating it, I cause a few problems that had to be fixed. (Don't accidentally arch the b+ to the heater wires on at the tube pin. Fried the rectifier and hum pot.)


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