Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: punkykatt on November 25, 2015, 06:24:06 pm
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http://el34world.com/charts/Schematics/files/ampeg/Ampeg_GS12R.pdf (http://el34world.com/charts/Schematics/files/ampeg/Ampeg_GS12R.pdf)
Hey Guys, Have a mid 60`s GS-12-R in for a good going over. Looks like the amp was modded several times over the years and the new owner said he turned it on and let the smoke out of it. Shorted power supply resistors. The trannys are still intact so he wants me to bring it back to life. While tracing thru the circuits to see what mods need to be undone plus all new E caps, diodes and PS R`s, I noticed the PT heater CT has its own circuit???. They have 330vdc on that 10M resistor. (See schematic above) Whats going on with that circuit, are they floating the heaters? A previous tech installed a virtual CT with the 2 resistors to ground. Can i remove the 10M, 1.5M, 0.1uf cap and tape off(heat shrink) the heater CT? Thanks much. Punky
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I noticed the PT heater CT has its own circuit???. They have 330vdc on that 10M resistor. (See schematic above) Whats going on with that circuit, are they floating the heaters? A previous tech installed a virtual CT with the 2 resistors to ground. Can i remove the 10M, 1.5M, 0.1uf cap and tape off(heat shrink) the heater CT?
That original circuit elevates the heater circuit to +43v. I'd rather have the original circuit than the mod by the previous tech. You don't want the virtual CT and the original elevated circuit, so one of them needs to be disconnected.
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Thank you.