03-29-2012, 10:53 PM
The power supplies that had to be used with the 10's and the 50's were a real nightmare to design, then build!
In the RCA "Tomcat" amplifiers, as used in the Victor Electrolas of 1925 through 1927, had to have this halacious power supply output voltage. Thy used a couple of 4 Mf. 1000 Volt caps in the main filters. That was no easy feat, either. They used an X99 tube as voltage amplifier to drive the 10. Its filament was supplied by a tapped resistor string, off of the output of the two 81's.
Because of the X99's critical voltage, line voltage had to be regulated by a big ballast resistor tube. AC power mains into homes could have been anything, and usually were. Sooooooo, the 876 (or 886) regulator tube did the job. That's that big hunker with the mogul base, that could heat an airplane hanger in Alaska.
More on power supplies. Mouser Electronics has some 2 Mf. / 1000 volt polypropylene caps that I use for the main filters in the Tomcat amplifiers. I parallel two on each side of the speaker field, and go away happy.
So now one more blow on power supplies. remember the movie: "The Jazz Singer"? It came out in 1927, with disk recorded sound from 16 inch discs, running at 33 1/3 RPM. The turntables ran off of the projector motors, to maintain sound sync. They had a big bank of speakers of some sort; probably the RCA "104" dynamics. There were transmitting tubes to drive the speakers, so that was no problem either. But, how about the B+ for the audio power amps??? They had a big bank of automotive storage batteries outside, or beneath the stage that were hooked in series for the HV B+ when the show was running in the evening, and the batteries paralleled on chargers during the day.
Resourcefulness always pays off big.
In the RCA "Tomcat" amplifiers, as used in the Victor Electrolas of 1925 through 1927, had to have this halacious power supply output voltage. Thy used a couple of 4 Mf. 1000 Volt caps in the main filters. That was no easy feat, either. They used an X99 tube as voltage amplifier to drive the 10. Its filament was supplied by a tapped resistor string, off of the output of the two 81's.
Because of the X99's critical voltage, line voltage had to be regulated by a big ballast resistor tube. AC power mains into homes could have been anything, and usually were. Sooooooo, the 876 (or 886) regulator tube did the job. That's that big hunker with the mogul base, that could heat an airplane hanger in Alaska.
More on power supplies. Mouser Electronics has some 2 Mf. / 1000 volt polypropylene caps that I use for the main filters in the Tomcat amplifiers. I parallel two on each side of the speaker field, and go away happy.
So now one more blow on power supplies. remember the movie: "The Jazz Singer"? It came out in 1927, with disk recorded sound from 16 inch discs, running at 33 1/3 RPM. The turntables ran off of the projector motors, to maintain sound sync. They had a big bank of speakers of some sort; probably the RCA "104" dynamics. There were transmitting tubes to drive the speakers, so that was no problem either. But, how about the B+ for the audio power amps??? They had a big bank of automotive storage batteries outside, or beneath the stage that were hooked in series for the HV B+ when the show was running in the evening, and the batteries paralleled on chargers during the day.
Resourcefulness always pays off big.
