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Ampeg Jet Volts (1966)
Hi, everyone, been a while...
I've got a Jet with 2 EL(?) brand 6C10s and 7591s. The problems are several, but right now I'm trying to fix just one of them.
The problem is V2, the Preamp/PI. The preamp plate is okay, but the cathode is about 50% higher than spec (3.5V). On the PI, the plate volts are about 25% below spec (150 and 130V), and the cathodes are running around 3.5-4V. Doesn't matter which tubes are there. Power tubes check out fine. Have tried replacing every cap in it exept the filter can (amps DEAD quiet with nothing plugged in and controls all up.)
Don't have a scope, but have a nice meter, and enough knowledge not to kill myself, if not my amp...
I've tried lowering the plate resistors to all three triodes, but that also didn't help the cathodes any. Amp has plenty of punch, but is dark w. a Tele and tone knob full up, and is quieter than my Champ. I'd like to get it up to spec before I start modifying it. My main concern is the cathodes being so high. Vague suggestions are welcomed; I'd like to try to figure out SOME of this myself...
Nice to see so many Ampeg posts here! Some of them have already been helpful. Thanks, Justin
I've got a Jet with 2 EL(?) brand 6C10s and 7591s. The problems are several, but right now I'm trying to fix just one of them.
The problem is V2, the Preamp/PI. The preamp plate is okay, but the cathode is about 50% higher than spec (3.5V). On the PI, the plate volts are about 25% below spec (150 and 130V), and the cathodes are running around 3.5-4V. Doesn't matter which tubes are there. Power tubes check out fine. Have tried replacing every cap in it exept the filter can (amps DEAD quiet with nothing plugged in and controls all up.)
Don't have a scope, but have a nice meter, and enough knowledge not to kill myself, if not my amp...
I've tried lowering the plate resistors to all three triodes, but that also didn't help the cathodes any. Amp has plenty of punch, but is dark w. a Tele and tone knob full up, and is quieter than my Champ. I'd like to get it up to spec before I start modifying it. My main concern is the cathodes being so high. Vague suggestions are welcomed; I'd like to try to figure out SOME of this myself...Nice to see so many Ampeg posts here! Some of them have already been helpful. Thanks, Justin