The Amp Garage

That would be incorrect. For one because your plate dissipation is incorrect. You said a 50 watt amp. And 6L6 isn’t 35 watts dissipation. Plate dissipation for this calculation isn’t about maximum power tube dissipation anyway. That number has nothing to do with how much AC output power an amp with ...

audiosalvage wrote: ↑Sat Apr 06, 2024 9:00 pm Loop circuit is completely removed from the amp and still no treble control. I checked the pot and all the tonestack wiring. Stumpted

Post pictures please and lift the capacitor leg and check that it has the proper capacitance.

A JTM45 power transformer SHOULD have 350-0-350 and that would get you 440-450 volts DC. They make for a great EL34 transformer. If you’re using cathode bias, you’ll be needing about 35-40 volts cathode voltage and you will subtract that from the B+ for figuring out power output. It still should be ...

I once considered building a similar device in the hopes of saving money. Fact is that I bought a PS100 for $700 and I love it. If I want to sell it I’ll get most of my money back and it’s just to easy to keep it. It allows so much more than just being an attenuator that it’s not feasible to build a...

When winding a transformer the lowest voltage winding sets the ratio of primary to secondary. Yes we want the 6.3 volt and 5.0 volt windings to be 100% correct at loaded output of 5.0 volts and 6.3 volts but the tolerance of the tubes is enough that perfection isn’t critical. My transformers actuall...

I’d test it for impedance ratio. Apply 100 volts AC to the full primary. It should be the blue and brown wires. A simple DC resistance check of the primary should make it obvious which of the three primary wires are the two plates and the center tap. Apply the 100 volts and write down the voltages f...

I’d put KT90’s in it and forget it. The bias is really close to EL34’s and they are basically the sound of EL34’s in a bigger bottle. KT88’s are also an option but the bias supply has to be modified.

Thanks for the suggestions. The first suggestion I have is to see if possibly you can pass something very thin between the outer paper insulation wrap and the lamination steel to break the varnish layer between the paper and steel. If that’s possible you then can begin to verify carefully attempt t...

What happens if you swap the 6V6 tubes between the sockets. Watch and record the current again.

And THAT Green wire doesn't go directly to the speaker lead,,, it goes into the tranny first.... I'm good there? thnx a mill~ॐ💃 20240209_001331.jpg Apparently when the transformers were ordered Ampeg specified an internal tap for the NFB which kept the wires closer to the board. It’s actually a goo...

Having a variac is a great thing. I’m going to suggest that you stop worrying so much about input voltage stability while checking voltages though. This is a situation that is pretty much out of your control and I find that while we want precise voltage stability, it’s nearly impossible. I have a de...

hebaton wrote: ↑Sun Jan 14, 2024 12:54 pm Hi, I am going to recap a 1968 Super Reverb. I have on hand 2 Sprague Atom 100UF @ 450V . THe originals are 70Uf @375
WIll feel of the amp change if I use those ? will this make it "stiffer" ?

Thank you !

F&T makes 80uF that will be better than the Sprague 100uF.

Greetings.... I've got some real hot 'n nasty amps that roast power tubes; Mesa, Budda, Vox, & Morgan, and I need a great sounding & heat/voltage handling set of tubes.... I recently read about some Preffered Series 7189's that can handle 400+v, and want to know what else is out there that might al...

It’s a lot more revealing to put 100-120 volts on the primary and measure the secondary than such a low voltage like 12 volts. YIKES!!! That could easily lead to death by revealing your susceptibility to heart stoppage by the AC mains. The vast majority of readers on this forum have no training and...

Thank you all for such informative and insightful responses. I will pull out a 12volt transformer I have somewhere here and do the voltage/winding ratio/impedance measurements and calculations. I've done that on a few OT's and its always landed the results nearly dead on the usual tap impedance's. ...