2nd opinion on a Sta Level PT

[substitute]

Hello, I'm planning out a sta level build and would like to use a power transformer I have sitting around.  It seems close to me, but I'd really like a 2nd opinion since I'm not sure how to calculate the B+ current draw of the sat-level circuit.

What I have is 500vct, 70ma.  The BOM for the drip build lists a few PT's, a hammond at 540vct, 120ma and a sower at 500vct 100ma.  I'm a bit worried 70ma isn't enough current, but I also saw that the hammond PT for a princeton reverb is only rated for 70ma, albeit at 640v. 

So, will the PT i have get the job done?

Thanks

 

[substitute]

Well, I was able to get the duncan PSU designer to work on my mac, so that was pretty instructive.  It seems the short answer to my question is under maximum circumstances, no.  Under average, yeah, probably fine.

Since I've been studying the schematic I've been wondering about using a more modern power supply design.  For the most part that's pretty easy to sort out but I'm a little confused about the circuitry around the cathodes of the 6AL5.  If I were to try and get rid of the OB2 tube what needs to happen in place of it?

 

[abbey road d enfer]

Hello, I'm planning out a sta level build and would like to use a power transformer I have sitting around.  It seems close to me, but I'd really like a 2nd opinion since I'm not sure how to calculate the B+ current draw of the sat-level circuit.

Just looking at the cathode voltages, you get 70mA for the 6V6's, 3mA+ for the 12AT7, 8mA for the 6386's and 3mA to feed the OA2, for a total of about 85mA. That would require a 120mA minimum rating for the transformer.

I'm a bit worried 70ma isn't enough current, but I also saw that the hammond PT for a princeton reverb is only rated for 70ma, albeit at 640v.

I find it hard to believe. It would just make it for a single-ended Princeton (5C-F), not a push-pull.

So, will the PT i have get the job done?

No, you'll just fry it.

 

[abbey road d enfer]

For the most part that's pretty easy to sort out but I'm a little confused about the circuitry around the cathodes of the 6AL5.

A resistive voltage divider derives 25V positive bias for the vacuum diodes in the 6AL5.

If I were to try and get rid of the OB2 tube what needs to happen in place of it?

Replace it with a 105V Zener diode of suitable rating. 105V x 3 mA = 415mW. I guess you should use a combination of Zener diodes in series that give the proper resulting voltage.

 

[substitute]

No, you'll just fry it.

Thanks, wishful thinking on my part.  I'm also realizing the meter I have on hand might not be appropriate for a sta level either.

And thank you for clarifying the OA2 question.