Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 3choplex on February 02, 2014, 02:14:05 pm
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I've been rebuilding that second 60s gibson scout someone gave me. It took a lot--rewiring basically 50% of the amp, including 2 new sockets that disintegrated. It's working now and sounds good. The voltages are very similar to my other scout.
But here's the weird thing. When I fire it up using a lightbulb limiter, the bulb lights then dims right away like normal, but after maybe 20 seconds lights back up and the indicator light on the amp dims. I'm not sure if it is fully lit or not, but I have gone over the wiring repeatedly and as i said, the voltages and sound are fine. Is it maybe that I am just not recognizing that the bulb is only halfway lit or something? I do find the indicator light going out curious.
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but after maybe 20 seconds lights back up and the indicator light on the amp dims.
Is the indicator a neon lamp connected to the AC mains? If so, there's nothing to worry about.
I'm guessing that the indicator behaves as expected when the amp is plugged directly into the wall?
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but after maybe 20 seconds lights back up and the indicator light on the amp dims.
Is the indicator a neon lamp connected to the AC mains? If so, there's nothing to worry about.
I'm guessing that the indicator behaves as expected when the amp is plugged directly into the wall?
Yes and yes.
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If the lamp glow very bright ( almost full , you use a 100 Watts ? ) there is a short . But many powerfull amp like Twin reverb , drive the amp full bright any time with no short .
When you power amp On lamp is close to full bright but after few second it dim a bit saying no short .
Don't forget when using lamp bulb all your voltages read lower than normal .
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> after maybe 20 seconds
Cold-start is just heater load. This is heavy for the first part-second then declines.
The tubes don't suck plate current until they warm-up, 10-20 seconds. Yes you expect a rise of wall-current at that point.
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I have 2 of them, and in both, V1 is a 12ax7, V2 and V3 are 6eu7s. Stock they are very bright and are clean all the way up. With the sprague sealed tone thingy bypassed, they are less bright and have a really nice compressed overdrive. I prefer the one without the tone thingy.