Hoffman 5E3 and 'bigger' PT and OT

[Bob Mc]

I have a Hoffman 5E3 board, and the chassis, power and output transformers from a Gibson GA35RVT. The GA35 originally had a SS rectifier, ran with 7591s and was about 35 watts. I do want to use (for a few different reasons) SS rectification and 6L6s for the finished project.

I am experienced in electronics and have basic tube skills (simple repair and maintenance of assembled amps), but a little overwhelmed by the thought of reverse engineering this project, so please humor me. I have just basic tools as well, and with an infant at home, I need to do my soldering at work after hours. Time is tight as well, I don’t have much debug time.

So let me start with the power section: the Gibby transformer has obviously higher voltage (the Gibson schematic reads 320V per side); the 6L6s won’t mind, but can the basic 5E3 (or at least Hoffman’s version) accommodate?
The Gibby rectifier was half wave, can I /should I change to full?
Bias?

Thanks!

[MWJB]

Are you sure about the half wave rectifier? The GA35RVT schem I saw was full wave - a diode from each leg of the secondary, meeting at the B+ rail.

The 5E3 circuit can take the extra voltage (final preamp voltages will be a little higher), if you really want to use 6L6s then maybe change the B+ to screen supply dropping resistor to 2.7K 3-5W (5E3 is 4.7K or 5K), add 470ohm 3-5W screen grid dropping resistors (look at any tolex 6L6 Fender tube socket layout), maybe use .022uf coupling caps at V1 pins 1 & 6.

5E3s are cathode biased, try 330ohm or 470ohm @ 10W from both pins 8 of 6L6s to ground (stock is 250ohms at 5W), 100v rated cathode bypass cap. 50mA-ish plate current should be OK.

6L6 OTs (4K-ish) run a lower primary Z than 7591 (6-7K), so reduce your speaker load by 33% to 50%.

[Bob Mc]

No, I was wrong

I was looking at the schematic this AM, and just logged in to correct my half wave comment (before I got caught saying something so stupid!).

Thanks for your time and the info, MWJB!!!