Strange Japanese PSU

[xtian]

So I have this PT salvaged from the Ace Tone BASE-3, with its 130vac HV. Schematics attached (look like Dead Sea Scrolls!). I don't recognize this style of power rail. How can I guess B+?

Alternative scheme to utilize 135v HT?

[Firestorm]

Voltage doubler isn't it?

[darryl_h]

It is a voltage doubler, so the B+ would be ( approximately ) 130 * 1.4 * 2 = 360VDC. The output valves' screen supply is taken from the mid point of the doubler, so it is approximately 180VDC.

The output valves' heater supply is taken directly from the incoming AC supply - before the power transformer. This could have serious consequences if there was a heater to cathode short.

If the transformer is to be reused with a more conventional heater arrangement, its 1A heater supply may not be sufficient. A separate heater transformer might be necessary.

[xtian]

Thanks, Darryl. Thinking about a Firefly, or somesuch.

[gingertube]

Daryl's B+ value is what you will get unloaded, that is 2 x the peak voltage. Once you start drawing current it will be more like 130 x 1.2 x 2 = 312 Volts. Assume somewhere between 300 and 320 V and you won't be far off.

Schematic says 400mA rated - that means 200mA max after the voltage doubler.

Ideal for a pair or quad of 6V6, 6BM8, 6GW8 6M5 (EL80) etc.

Would also be fine for a lowish power cathode biased push pull EL34 (about 25 Watts) for which the output tranny would also be suitable. The tranny set would also suit a quad of 6V6 or 6BM8.

No troubles powering a Firefly.

For more guidance here is the data for those weird output tubes
http://www.mif.pg.gda.pl/homepages/fran ... 0H-B26.pdf

If you look down at the Class AB Push Pull data it shows 47 Watts into 3K5 with B+ of 300V.

Cheers,
Ian