Original PA 774 and 5AR4

[Bob Smith]

I think Ed Brown answered this near the end of the "PA 774" thread, but want to be sure I understood the answer. I'd like to use an original PA 774 (from an SCA-35) to build a tube-rectified DIY-35. It appears that the specs are fine, except that I'll need to add a 5V filament transformer. Is this correct?

[Shannon Parks]

Hi Bob,

It can be done with the extra filament tranny, but you'll be lopping off enough B+ to hurt your max output power. So if this amp ends up in an office or study, it won't be much of an issue. Likewise, I would look at the 272JX (or the nicer ones) if I wanted to crank it now and then.

My poor neighbors will tell you what I would probably do. Yellow_Light_Colorz_PDT_09

Shannon

[Bob Smith]

Shannon,
Thanks-- I think I'll follow your recommendation since the 272JX isn't that expensive. Should I expect the same plate voltage as in the DIY-35 manual (i.e. 360V)?

[Shannon Parks]

Shannon,
Thanks-- I think I'll follow your recommendation since the 272JX isn't that expensive. Should I expect the same plate voltage as in the DIY-35 manual (i.e. 360V)?

Hi Bob,

You should see at least 370V, I think.

Shannon

[Bob Smith]

Shannon,
Thanks for the info. I guess all that's left is to order some parts, buy lots of band-aids, prime the bagpipes and start up the chainsaw.

[Shannon Parks]

Shannon,
Thanks for the info. I guess all that's left is to order some parts, buy lots of band-aids, prime the bagpipes and start up the chainsaw.

And don't forget the duct tape.

Shannon