Power transformer question.

[Dingleberry]

Hi.
Gutted an old Steelphon Pioneer amp, Italian "vintage" from 1969.
It was actually very unpleasant sounding piece of spaghetti western history... Shrill and harsh nasally top end and thousands of tons of unuseable low end and nothing in between...

I was planning to use OT and the chassis/head cab in a wreck-style project sometimes in the future and use the PT for my next build. My question is will the power transformer be capable of producing enough juice for my next build (2xECC83 and 2xEL34/KT66)?

The amp had originally 4xEL84 output section, fixed bias. ECL86 reverb driver, 4xECC83 in preamp and one ECC81 as P.I.

I calculated the currents from datasheets and with that tube layout the power tranny should at least give 5,24A filament current and 243,4mA B+ current. So if I calculated right it should be plenty for 2xECC83 and 2XEL34/KT66.

The power transformer was putting out (without any load) 6,9V for filaments and 330V for B+ and 32V for bias. (230V into 220V tap)
I assume that I have to use the bias voltage doubling circuit
(alá Hiwatt mod.) to get it to proper range with EL34/KT66.
Under load those voltages will drop a bit of course and probably get the filament voltage down a bit,although it's still in the 10% margin... but at first glance it sounds to me that it would be a good match for my next amp.
What you guys think, does this make any sense?

-T

[Phil_S]

This sounds reasonable. I wouldn't be too concerned about the bias circuit. You can probably tweak it to give you what's needed. With the right combination of caps and resistors, getting a 10-15V boost from the transformer output shouldn't be too difficult.

If it doesn't work out, you can always tap the HT secondary for bias voltage, Marshall style. The difference between 220 and 230 is only about 5% and that's within the ordinary margin of error.