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Brief background on this amp. Bought the Princeton Reverb SF in a pawnshop about 15 years ago, not working well. Original cabinet had been chopped into "head". It was my first tube amp, I got it running, and it is what I learned my tube amp chops on. It has been modified and experimented with many times, including some short periods when I played it with 6L6's in it. This was before I understood the filament current limits in the Princeton power tranny. In spite of that abuse, I apparently didn't harm it. Recently I picked up a nice reproduction Princeton cabinet with a 12" baffle and decided to restore the old Princeton. There are almost no original components in it, but the circuit is close to original.
I reduced the size of the coupling cap going into the PI to cut out some of the bass, put 470 ohm screen resistors and 1.5K grid stoppers on the outputs. I replaced the original output tranny with a Mercury Magnetics Deluxe Reverb tranny that has 2,4, and 8 ohm taps, so I can use my 4 ohm Vintage 30 in it. I'm also using a 5AR4 rectifier. I added bias control mounted where the vibrato pedal goes. I set the bias at 24ma. Plate voltage is 420 so it's idling around 10 watts. I have a new matches set of JJ 6V6 outputs in it.
The other night, after playing it for a while, I turned down the volume and left in on for a few hours. My intention was the burn the tubes in and recheck the bias later. I notice a hot smell. It was in a dark corner of a room and there were no glowing tubes or smoke, but when I touched the power tranny it was too hot to keep my finger on it!!
Because this is the first time I've ever left it on for several hours, I don't know if this is normal. I'm thinking it's possible I may have damaged the filament windings long ago when I put 6L6 outputs in it. So, I'm thinking about replacing it, and I found out that Allen amps sells a heavy duty drop in replacement for it that has more secondary and filament current capacity, that would allow me to safely use 6L6s if I wanted to, although I'm pretty happy with the sound of the 6V6s in it now.
The question is, should the power tranny be getting too hot to touch after idling for several hours?
I reduced the size of the coupling cap going into the PI to cut out some of the bass, put 470 ohm screen resistors and 1.5K grid stoppers on the outputs. I replaced the original output tranny with a Mercury Magnetics Deluxe Reverb tranny that has 2,4, and 8 ohm taps, so I can use my 4 ohm Vintage 30 in it. I'm also using a 5AR4 rectifier. I added bias control mounted where the vibrato pedal goes. I set the bias at 24ma. Plate voltage is 420 so it's idling around 10 watts. I have a new matches set of JJ 6V6 outputs in it.
The other night, after playing it for a while, I turned down the volume and left in on for a few hours. My intention was the burn the tubes in and recheck the bias later. I notice a hot smell. It was in a dark corner of a room and there were no glowing tubes or smoke, but when I touched the power tranny it was too hot to keep my finger on it!!
Because this is the first time I've ever left it on for several hours, I don't know if this is normal. I'm thinking it's possible I may have damaged the filament windings long ago when I put 6L6 outputs in it. So, I'm thinking about replacing it, and I found out that Allen amps sells a heavy duty drop in replacement for it that has more secondary and filament current capacity, that would allow me to safely use 6L6s if I wanted to, although I'm pretty happy with the sound of the 6V6s in it now.
The question is, should the power tranny be getting too hot to touch after idling for several hours?
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