I was told to use a screwdriver and touch the cap with one end and then touch the side of the screwdriver against the chassis. Is this correct? Will the electricity in the cap go through the plastic handle of a craftsman screwdriver and shock me? I want to make sure since I have a mod coming up and I don't want to kill myself doing it. Thanks.
Chris
I take this approach:
Instead of using pliers to hold the 10watt resistor I use a alligator clip with insulated wire attached on each end.
If you haven't done so already I suggest going to the local book store and buying some books on amp(& guitar) repair. Some great ones are by Donald Brosnac, Ritchie Fliegler and Craig Anderton.
Well I guess you haven't managed to kill yourself just yet discharging any caps.
By far and away the easiest way is to flick the power off on the amp with the standby left on. It won't hurt the tubes, and the power will dissipate even quicker if you play a chord through the amp as the power fades. When you can't hear anything from the speakers, your caps ought to have discharged safely. Don't forget to disconnect the mains supply afterwards though! (Sounds obvious, but it's easy to get complacent!)
Catdaddy's advice works on most circuits as long as the tubes are fully warm, and is how I do it after I've proven to myself that it works with the particular chassis I'm working on. Always check with a multimeter to make sure. The resistor/alligator clip method works well too, and is probably the "official" method. Just don't forget and leave them in there.
Don't short them with a screwdriver. Although it will work, it's hard on the caps and could be dangerous. Sounds to me like you should do some more reading. Don't take that as a slight: I often re-read my books for hours before diving back in. I'm only a hobbyist, and mistakes happen very quickly when doing this work.
I have to re-stress the importance of good habits. For a while I got slack and found myself going back to work with the mains still plugged in after checking out my mods under power. Train yourself to ALWAYS unplug the amp and drain the caps, and check with a multimeter, EVERY TIME, even if you're confident you followed every measure, and only probe around with a sharpie or something non-conductive, not a screwdriver, even if it has an insulated handle it can still short something. Trust me on the importance of this.
Way too complicated. I just give it to "my guy" (that's Chicago-speak for "my repair person").
If you use the alligator clip/resistor method, just short the terminals out with a wire afterwards and the caps won't get any charge back (which they can do). But make sure you take the jumper wire off before powering the amp back up again!
Put the alligator clip on pin 1 of a preamp tube. That way, the caps will drain through the 100K plate resistors over a period of several seconds. This is much friendlier to the caps.
