tizman,
Forget about your plan in Post # 19 to use a center tapped 12.6V filament secondary to buck a center tapped B+ winding.
You would have to unwind all the 12.6V turns and all the B+ turns, and then insert/ connect the 1/2s of the 12.6V turns between the 1/2s of the B+ turns (and with each 1/2 of the 12.6V turns out of phase with each 1/2 of the b+ turns ).
Can not be done unless you are both a sadist and a masochist.
Your solutions for using that power transformer to power a stereo 45 amplifier using are:
1. Use a Buck winding secondary of an independent transformer in series with your transformers primary.
Can not be done, because you have no room, Right?
Then use an external box and transformer, just as wrenchone said in post # 20 to provide a Bucked power out to your amplifier.
Or box up a tapped power voltage adjustment in a box, to power your amplifier.
2. Use a Choke input Power supply to drop the B+
You already have a choke in your B+ power supply, Right? Just put it in front of the first filter cap.
That changes the power supply B+ filter to Choke input.
Of course, that tends to drop the B+ by the ratio of 0.9/1.4, which is probably too much, you can fix that by using a small capacitor in front of the choke input filter, perhaps a 0.5uF, 1uF, 2uF cap as necessary to get the B+ you want.
Or use a true choke input filter, and change the rectifier tube to solid state diodes, to get back some of the lower voltage choke output.
3. If you are using fixed bias, or are using adjustable fixed bias; then change the circuit to self bias. Self bias gets rid of 56V of B+ (eaten up in the self bias voltage).
But that is difficult to do, unless you Either have 2 independent 45 filament supplies (so you can use independent self bias resistors),
Or unless you have very well matched 45 tubes.
Be flexible, short of moving to an alternate universe (or to a location that has wimpy power mains) then use one of the above solutions, or be prepared to junk that old organ power transformer, and $pend the $ for a new power transformer.
Just my opinions and just my experiences.
Have fun!
Forget about your plan in Post # 19 to use a center tapped 12.6V filament secondary to buck a center tapped B+ winding.
You would have to unwind all the 12.6V turns and all the B+ turns, and then insert/ connect the 1/2s of the 12.6V turns between the 1/2s of the B+ turns (and with each 1/2 of the 12.6V turns out of phase with each 1/2 of the b+ turns ).
Can not be done unless you are both a sadist and a masochist.
Your solutions for using that power transformer to power a stereo 45 amplifier using are:
1. Use a Buck winding secondary of an independent transformer in series with your transformers primary.
Can not be done, because you have no room, Right?
Then use an external box and transformer, just as wrenchone said in post # 20 to provide a Bucked power out to your amplifier.
Or box up a tapped power voltage adjustment in a box, to power your amplifier.
2. Use a Choke input Power supply to drop the B+
You already have a choke in your B+ power supply, Right? Just put it in front of the first filter cap.
That changes the power supply B+ filter to Choke input.
Of course, that tends to drop the B+ by the ratio of 0.9/1.4, which is probably too much, you can fix that by using a small capacitor in front of the choke input filter, perhaps a 0.5uF, 1uF, 2uF cap as necessary to get the B+ you want.
Or use a true choke input filter, and change the rectifier tube to solid state diodes, to get back some of the lower voltage choke output.
3. If you are using fixed bias, or are using adjustable fixed bias; then change the circuit to self bias. Self bias gets rid of 56V of B+ (eaten up in the self bias voltage).
But that is difficult to do, unless you Either have 2 independent 45 filament supplies (so you can use independent self bias resistors),
Or unless you have very well matched 45 tubes.
Be flexible, short of moving to an alternate universe (or to a location that has wimpy power mains) then use one of the above solutions, or be prepared to junk that old organ power transformer, and $pend the $ for a new power transformer.
Just my opinions and just my experiences.
Have fun!
I speculatively looked at my AC mains voltage, and it's 123VAC. I'm retrofitting an old Scott 399 receiver for a friend, and I'm seriously considering an external bucking transformer, as the modern mains voltages may be a bit much for that 50's tube receiver. A grounded power cord wouldn't hurt, either.
I get the first feed from the pole transformer at the back corner of my property, so it's no surprise that my mains voltage is a little on the high side. I had to install a UPS with heavy surge suppression, too, as I'm also first in line for all the crap that comes down from the pole. I live in downtown San Jose, and I've come to believe that the power infrastructure is a bit old and tired. I've had far more power outages at my new location than I've had at my old house.
I get the first feed from the pole transformer at the back corner of my property, so it's no surprise that my mains voltage is a little on the high side. I had to install a UPS with heavy surge suppression, too, as I'm also first in line for all the crap that comes down from the pole. I live in downtown San Jose, and I've come to believe that the power infrastructure is a bit old and tired. I've had far more power outages at my new location than I've had at my old house.
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The power supply is already choke input. An external 12.6/6.3 Volt transformer in series to buck the primary is probably the route I’ll take. I have a few appropriate transformers at hand. Thanks for your input.