need advice to spec power transformer

[Leo_Gnardo]

If it is also hooked up to the B+, then it was being used to lower the original B+ voltage by 4.3 volts.

Wonder what was the point of adjusting B+ by only 4.3V ? I could see, say 30V or more. 4.3V, why bother?

I'd say ignore that zener & just get 'er fixed with no fancy zener extras.

[Jazz P Bass]

Oops.
Bit by Google.
It is a 50 volt/ 50 watt zener diode.
Link: http://www.vetco.net/catalog/product...oducts_id=4343
Now that makes a bit more sense.

[Leo_Gnardo]

Oops. Bit by Google.
It is a 50 volt/ 50 watt zener diode. Now that makes a bit more sense.

OK yes now it does. And it looks like you landed on a likely candidate transformer, no zener needed. All is good.

[fredcapo]

OK yes now it does. And it looks like you landed on a likely candidate transformer, no zener needed. All is good.

Ok. I will chuck the diode, and look at the b+ when I install the new ps. Hopefully it will be in the ballpark. I just hope the Zener is not part f some exotic basing scheme. (see below wishful thinking)

I think I'm going with a Hammond 270HX which is 275-0-275 @ 200mA. I'd rather go easier on the plates and have current capacity to spare...right? Setup an account with CE so might as well use it...

I still have not drawn up a schematic to try to figure out how the bias s generated, but since the Zener is all by its lonesome on the ct, I don't think it is part of the bias supply, and since there was no tap off the pt for bias I should not need one... Recall this is a home brew amp that I am only working on because, well no good reason. Thanks for all of the input.

[Leo_Gnardo]

I still have not drawn up a schematic to try to figure out how the bias s generated, but since the Zener is all by its lonesome on the ct, I don't think it is part of the bias supply, and since there was no tap off the pt for bias I should not need one... Recall this is a home brew amp that I am only working on because, well no good reason. Thanks for all of the input.

Either you have to have a self-bias, with a resistor between the output tube cathodes and ground, or you have to generate a negative voltage for fixed bias. (Unless this amp has the very rarely seen and never in guitar amps "back bias." We'll leave that possibility aside for the moment.) If no bias tap, no worry, you can use a 1W resistor say 100K to 180K off one of the high voltage windings, silicon rectifier and 20 to 100 uF cap, say 50 to 100V rated. Lots of Fenders and Marshalls get their bias this way. Might have to try a couple different resistors to get bias voltage in the right ballpark.

No bias, hm maybe that's the reason the PT melted down in the first place. Don't follow in those footsteps.

[Jazz P Bass]

Look on the output tube plates, pin 8.
They are either tied to ground (well, maybe a snarky one ohm resistor & then ground) or they are attached to a high wattage resistor.
I am thinking maybe the amp is like a Fender 57 Deluxe.
http://support.fender.com/schematics..._schematic.pdf