5F1 transformer / rectifier / voltage question

[squierstrat]

I've built my first amp, a working 5F1. Yay! However... all the voltages are somewhat high.

I used a Classictone 40-18019 power transformer in a "champ" bundle, I think this was a mistake for tweed/5F1. After one bias adjustment attempt here is where I'm at:

- PT red output 343vac on each rectifier pin.
- B+1/2/3 are 422, 369, and 324 vdc.
- V1 12AX7 voltages pin 1 216v, p3 1.5v, p6 207v, p8 1.575v
- V2 6V6 voltages pin 3 394v, pin 8 24.8v, cathode resistor 580 ohm, plate dissipation 14.9 watts

Options for your advice

- Buy a different PT. (Recommendations?)
- Do different 5Y3s have different output? I have a new Sovtek now.
- Is it a bad idea to put a resistor between the rectifier output and B+1?

Thanks.

[tubeswell]

...
- Do different 5Y3s have different output? I have a new Sovtek now...

You should get about 370 or 380 with a proper 5Y3 (The Soviet '5Y3' is not a proper 5Y3 - it delivers higher voltages).

Having noted that, a JJ 6V6S should be able to handle 14.9W with a chunky Rg2 IMO. (Even tho you'd be running it over its published ratings). But I wouldn't run a proper 6V6 under such conditions. YMMV

[texwest]

The new production 53 tubes will make a hotter B+.

NOS NIB 5y3 tubes are very cheap and are a no brainer.  You can buy a never used on on Ebay for  $15-20.

[texwest]

Mojotone has a heyboer made Champ PT with a lowered secondary voltage of 290-290v.   The Weber's champ PT has secondaries that run at 330-330 or 300-300.   The Hammond has a 275-275 secondary.

[squierstrat]

Thanks all.

I'm going to start by looking into different 5Y3 and maybe Rob Robinette's Zener diode mod. https://robrobinette.com/Generic_Tube_Amp_Mods.htm#B+1_Voltage

Bookmarked a better PT. https://www.mojotone.com/amp-parts/Power-Transformers/Tweed-Champ-Power-Transformer-120V-240V

[HotBluePlates]

Mojotone has a heyboer made Champ PT with a lowered secondary voltage of 290-290v.   The Weber's champ PT has secondaries that run at 330-330 or 300-300.   The Hammond has a 275-275 secondary.

I've also noticed several replacement PTs (that have DCR specs available) have lower DCR than the original power transformers in my vintage amps.  True for the blackface Champ/Princeton PT compared to my '65 Vibro Champ.

There would be some amount of B+ increase due to that lower DCR in the modern part.

[tubeswell]

...
Rob Robinette's Zener diode mod. https://robrobinette.com/Generic_Tube_Amp_Mods.htm#B+1_Voltage

FWIW, Rob didn't invent that. He only plagiarised it from somewhere else, like the rest of the stuff on his website