So I got two stereo Wollensak tape machines for cheap, and intend to use the power transformer for a 6AQ5 stereo amplifier. While they are being shipped, I downloaded the schematic (of a mono Wollensak, couldn't find t-1515 stereo schem) and saw this for the power supply:
I know a little about power supplies, but this I don't understand. Is Wollensak using line voltage to make filtered 250 VDC?? Is there a way to make this transformer (I assume the stereo one is same) work in a 6AQ5 amp, or ought I just look for a more conventional PT? Thanks!
I know a little about power supplies, but this I don't understand. Is Wollensak using line voltage to make filtered 250 VDC?? Is there a way to make this transformer (I assume the stereo one is same) work in a 6AQ5 amp, or ought I just look for a more conventional PT? Thanks!
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I can see my text & image. Reload? If not, here is the power schematic: https://images.weserv.nl/?w=800&t=f...ploads26/Wollensak_power_supply1585545276.jpg
The thread is fine now.This is a very old circuit.
The 250VDC comes from the voltage doubler.
Unfortunately, the B supply return (B-) is either connected to Neutral,
Or it is connected to to the Hot power lead, through R29 (22 Ohms) and the diode at M. It all depends on which way you plug the power cord in.
The above condition is considered unsafe in many countries today.
And that is for a good reason (shock hazard).
The Red and Orange secondary is 1300 Ohms DCR. It is not going to be able to run a pair of 6AQ5 tubes without getting very hot, and possibly catching fire.
Safety First!
The 250VDC comes from the voltage doubler.
Unfortunately, the B supply return (B-) is either connected to Neutral,
Or it is connected to to the Hot power lead, through R29 (22 Ohms) and the diode at M. It all depends on which way you plug the power cord in.
The above condition is considered unsafe in many countries today.
And that is for a good reason (shock hazard).
The Red and Orange secondary is 1300 Ohms DCR. It is not going to be able to run a pair of 6AQ5 tubes without getting very hot, and possibly catching fire.
Safety First!
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The previous safety warnings must be taken to heart. What those power trafos can provide is heater current and small signal circuitry B+. Fortunately, safe implementation of a voltage doubler O/P tube B+ supply can be done at modest expense. A Triad N-68X isolation trafo will comfortably feed 2X 6AQ5s or other "12" W. power O/P types.
BTW, full wave bridge rectify the red/orange winding and get the residual hum level down.
Larger caps. in the doubler stack are consistent with current practice. Back in the day, cost and space considerations closed that choice out.
BTW, full wave bridge rectify the red/orange winding and get the residual hum level down.
Larger caps. in the doubler stack are consistent with current practice. Back in the day, cost and space considerations closed that choice out.
Thanks for the replies with safety warnings. I think what I'll do with these is set them aside, maybe to one day implement Eli's voltage isolation doubler, or possibly use them to build a preamp. Thanks again!
