Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jim on April 21, 2013, 07:34:34 pm
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My fuse went during a gig last week. My amp was sounding fine. I replaced it and finished the gig assuming there was some sort of power fluctuation. Now last night, the same thing happened. Both times I was kind of loud but the amp seemed well behaved. Recently I had replaced my 6V6GT's with another set of JJ's and I bumped up the bias current 5ma to 25ma/tube. Could this small increase have something to do with it? or should I look for something else. The amp has always had a AC fan , big iron, and a LP overdrive mod when I built it and I have never had this situation in the past. I Should I worry about this new tube set or just increase the fusing to 3AMP/SB (or FB?) and forget about it. Jim
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2 Amps at 120V is 240 Watts.
There's _NO_ way a couple 14W 6V6 can be sucking 240 Watts.
Something in there must be HOT, like a 200 Watt lamp.
Solid or vacuum rectifier?
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5AR4 with diodes for PIV. Same as always. The only thing new is the power tubes. I guess I have to look inside the chassis. Bias current is stable and tubes match. No hum and sounds good. Strange. Jim
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Deluxe Reverb spec is a 1A fuse (http://www.el34world.com/charts/Schematics/files/fender/DELUXE_REVERB_AB763.pdf).
You might have issues with filter caps or bias circuit, a failing tube/rectifier or some other intermittent high current draw.
I'd stick with 1A slo-blo, and maybe check the amp with a lightbulb limiter in place.