Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jeff967 on June 10, 2011, 10:40:52 am
-
please help, I am having a witts end problem. with a 5y3 rectifier circuit. have tried a dozen different tubes all champ tested good. we have 5.7 volts on yellow heater wires and they are on pins 2 and 8. and have 311 volts on red primary wires on pins 4 and 6, with center tap going to ground on transformer mounting bolt. the B+ off pin 8 measures 130 volts. what is going on here?
-
You need to have it connected to a filter capacitor before full voltage can be measured.The filter cap reduces the last bit of AC ripple so you can accurately measure it with your meter.
If you have already built the amp,then look for a bad ground at the first filter capacitor or bad grounds overall.
-
I think we have a bad JJ cap can here. I have not bit the bullet and bought a cap meter :BangHead:
-
I think we have a bad JJ cap can here. I have not bit the bullet and bought a cap meter :BangHead:
Where and/or how is the JJ cap can grounded? You mentioned that the PT center tap was grounded on a transformer bolt. Best practice is to ground the PT center tap directly on the negative end of the "reservoir" cap (first one after rectifier). In this case, that means the cap can's ground. Then tie the cap can's ground to your mounting bolt. This minimizes the current loop between the PT and the reservoir cap. It also reduces the number of solder connections which could be bad for one reason or another.
HTH
Chip
-
I think we have a bad JJ cap can here. I have not bit the bullet and bought a cap meter :BangHead:
Best practice is to ground the PT center tap directly on the negative end of the "reservoir" cap (first one after rectifier). In this case, that means the cap can's ground. Then tie the cap can's ground to your mounting bolt
it is wired jest like that.