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Hi folks, on my hobby bench today is an old Regal Muscial Instruments Co. Model 250 amplifier. Unsure of the date on it.
A friend brought it over as 1 6V6 is not heating up and no sound. He bought it as is on Ebay. I got in and started researching.
I think I have found the problem, but am not 100% sure how to fix it. Heater wires seem wired incorrectly.
I have no schematic, and my knowledge is limited. Here is what I know so far:
Someone was in the amp and installed new caps. I am pretty sure they mixed up the wiring.
Tubes are: 30 rectifier. 1 6SC7 (Phase Inverter?) , 2 6V6 Power Tubes and 1 6C8 (pre-amp?) Could anyone confirm my guesses on the tube positions?
Is the 6SC7 some type of phase inverter?
According to my research the 6SC7 tube heaters are pins 7&8. I have 5.3V AC out of the PT going to pins 2&7 on the 6SC7.
I am pretty sure someone was confused as pins 2&7 are supposed to be the heater pins on the adjacent 6V6 tubes. I'll plan to re-wire that.
The other questions I have are there appear to maybe be some other incorrect wires on the 6SC7 pins 7&8, instead of the heater wires.
If anyone has some type of schematic, close this this amp, that would be much appreciated. If we can't get a schematic I will post more pics
and details, I suspect someone here will be able to guide me along. Much appreciated. Thanks, Keith.
Left to Right in image: V1 6C8, V2 6V6, V3 6V6, V4 6SC7, V5 80 Rectifier. You can see the heater wires from the PT going to pins 2&7 on V4.
Maybe the 6SC7 is supposed to be in V2? 6V6s in V3 & V4?
Tried swapping tubes....LOL. Got it. 6SL7 in wrong position. So it's not a PI. How do these 2 6V6s' push? Class A? Thx.
A friend brought it over as 1 6V6 is not heating up and no sound. He bought it as is on Ebay. I got in and started researching.
I think I have found the problem, but am not 100% sure how to fix it. Heater wires seem wired incorrectly.
I have no schematic, and my knowledge is limited. Here is what I know so far:
Someone was in the amp and installed new caps. I am pretty sure they mixed up the wiring.
Tubes are: 30 rectifier. 1 6SC7 (Phase Inverter?) , 2 6V6 Power Tubes and 1 6C8 (pre-amp?) Could anyone confirm my guesses on the tube positions?
Is the 6SC7 some type of phase inverter?
According to my research the 6SC7 tube heaters are pins 7&8. I have 5.3V AC out of the PT going to pins 2&7 on the 6SC7.
I am pretty sure someone was confused as pins 2&7 are supposed to be the heater pins on the adjacent 6V6 tubes. I'll plan to re-wire that.
The other questions I have are there appear to maybe be some other incorrect wires on the 6SC7 pins 7&8, instead of the heater wires.
If anyone has some type of schematic, close this this amp, that would be much appreciated. If we can't get a schematic I will post more pics
and details, I suspect someone here will be able to guide me along. Much appreciated. Thanks, Keith.
Left to Right in image: V1 6C8, V2 6V6, V3 6V6, V4 6SC7, V5 80 Rectifier. You can see the heater wires from the PT going to pins 2&7 on V4.
Maybe the 6SC7 is supposed to be in V2? 6V6s in V3 & V4?
Tried swapping tubes....LOL. Got it. 6SL7 in wrong position. So it's not a PI. How do these 2 6V6s' push? Class A? Thx.
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