PT for AC30/4 build

[Mark]

The Mercury Magnetics AC-30 power transformer is 303 - 0 - 303vac. God only knows why they prefer higher rail voltages.

I will use the Zener mod to lower the voltages.

[Roe]

It depends on the rail voltages too. I’m using an 82 ohm resistor in an AC-30/6 repair as it has a rail voltage of 350vdc. Using a 50 ohm resistor would simply destroy the output valves.

The output stage is pretty much going flatout at rail voltages of 300vdc, there’s no point adding to its woes.

The 82 ohm resistor sounds fine in grey panel AC-30 amp though the rail is greater than the expected rail voltage.

If I could only get rid of the channel bleed.

yes, 50R with more than 330v is risky. But those russian 6p14 tubes may work. And reducing the b+ voltage is possible.

[Mark]

Roe, the 6P14’s are good as they can withstand higher voltage and the plate dissipation is 14 watts instead of 12 watts. I think the screen dissipation is 2 watts which is the same as a regular EL-84.

[pdf64]

Roe, the 6P14’s are good as they can withstand higher voltage and the plate dissipation is 14 watts instead of 12 watts...

Unfortunately we don't know the details of the Russian / Soviet era rating system used, by which the 6P14 is deemed to have a 14W plate dissipation limit. In the absence of that, comparing the numbers is a bit apples and oranges. Consider that if a design max rating was available for EL84, it seems reasonable to assume that it would be about 14W, in the same way that the 6V6 has a 12W limit under the design centre system, but a 14W limit design max.
See http://www.one-electron.com/Archives/RC ... 0Tubes.pdf
https://tubedata.altanatubes.com.br/she ... 6V6GTA.pdf
https://tubedata.altanatubes.com.br/she ... 6V6GTA.pdf