rphancock1
Member
- Joined
- Aug 14, 2018
- Messages
- 17
I’m working on the second of a pair of Berlant Concertone preamps and have a question about the heater voltages I’m finding. The first sounds great after I set up new input and output transformers, however the second passed a little quiet and distorted audio before going quiet. Since I didn’t see any glowing filaments in the preamp tubes I checked the voltages against the functioning one. What I was surprised by was the voltage in the functioning preamp... as spec’d In the heater schematic below, there is about 25 volts going into the rectifier. Then, the voltages vary widely on different tubes heater pins, from 14 volts on a 4,5 pin combo to 4 volts on a pin 9, even zero volts in one case.
Can anyone explain this to me? Happy to provide a tube by tube voltage if it helps, but I was expecting to find something closer to 12 or 6 volts on each pin. I’ve only built ac heated circuits before.
Thanks
Can anyone explain this to me? Happy to provide a tube by tube voltage if it helps, but I was expecting to find something closer to 12 or 6 volts on each pin. I’ve only built ac heated circuits before.
Thanks