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Using it as a tool to run my amps to spec is really all I use mine for. Maybe a tad under-spec on my Marshall JTM45/100 at 110v. 560 volts on the screens is hella hard on modern KT66’s.

If your rectifier is from the 90’s like mine, it will actually run more in-spec if you run it at ~117VAC instead of modern voltages (122-126V average). The amp runs hotter at 120-125VAC. Like I mentioned, I went off the heater voltages and made sure they’re running at their intended voltages...

I have installed an adjustable bias (using the 25K return send pot since I also performed the series loop mod and I currently use the same Variac he used but I only drop to around 115VAC so that the heaters are seeing 6.3v for power and preamp tubes and 5v for the rectifiers. Otherwise, they...

Precisely. And that’s the schematic voltages when the amp is expecting 117VAC. Now with modern AC voltages, those numbers will be even higher.

For four years, I both lived in Colorado and had good bud. lol. But that’s my company name. I work on and build guitar effects. Then started working on and building amps when covid hit. But now I have **** bud living back in Texas. lol I think to better illustrate this, I’d be better off...

I believe I’ve compiled a fairly accurate chart indicating approximate idle dissipation, idle current, and associated Mesa Color coding at ~475v Plate Voltage. This chart does not apply to Simul Class amplifiers, btw. On my 90’s Dual Rec, I installed an external bias control to more-closely...

I made a couple charts of estimations of approximate plate dissipation at 470v, idle plate current, and Mesa Color codes for 25 and 30 watt tubes in NON Simul-Class Mesa amplifiers (Rectifiers and such). As you’ll see below, I wouldn’t shoot for 70% plate dissipation. Mesa shoots for around...

This is what a proper conversion should look like if you want it to look stock. Switchcraft 112A jack and this configuration. PS - I got rid of that solder blob after this pic. 😂

Yeah, the no load pot trick wouldn’t work on the loop. It would remove the wet signal instead of the dry signal. I’ll upload a pic of the serial loop mod I did yesterday. I forgot to take a pic when I did it so I’ll have to open the amp back up.

So you have to have a cable connected for it to work? Then, he did it the easy way and not using a shunting mono jack for the return jack and a link between jacks when fx loop not in use. I also have a theory that I can’t believe no one has posed: using a no-load pot to take out all 100% of...

You should be able to click on the pic and will take you to a PostImage link and will show the pic.