Rodabod wrote:

ApeLincoln wrote:what do you mean where 'B+' attaches? and how would I tell the power supply capacitor from others?

Related question - can you shock yourself on the older, smaller paper & wax capacitors as opposed to the 'can' capacitors?

B+ or HT (high tension) refers to the the high voltage used by the valves. There are associated caps which filter mains to provide this B+ voltage and these are found in the power supply section. They should be drained before work ideally.

Generally speaking, you'd only expect to receive a bad shock from a larger electrolytic can capacitor found in the power supply section. You can locate these by using a schematic or by tracing what you can see in the circuit from the mains incoming.

Rather than jump straight into valve amp theory/maintenance, I'd suggest you study a little basic electronics first as otherwise you may well find yourself kind of half-knowing bits and bobs and ending up never fully sure about what you are doing.

Something like this might be good for starters:

http://www.electronics-tutorials.com/ba ... ronics.htm

Related question - can you shock yourself on the older, smaller paper & wax capacitors as opposed to the 'can' capacitors?

madraso_ wrote:once you have done this, it is also not a bad idea to attach a bleeder resistor to the plate pin (1 or 6 on any preamp tube) so that the electrolytic capacitors do not "build back" some (potentially large) portion of their original charge. Just make sure you remove it when you are done working and ready to turn the amp on....

benadrian wrote:

madraso_ wrote:once you have done this, it is also not a bad idea to attach a bleeder resistor to the plate pin (1 or 6 on any preamp tube) so that the electrolytic capacitors do not "build back" some (potentially large) portion of their original charge. Just make sure you remove it when you are done working and ready to turn the amp on....

I just hook up and alligator clip jumper between pin 1 of the preamp tube and the chassis whenever I have the amp open. Also, remember to put the amp standby in "play" position.

I spent Saturday morning with my hands in a noisy, oscillating Laney Supergroup. What a damn pain. It's a case of tidiness begetting noise problems. It's no use to make the inside of the amp look pretty if that prettiness is the reason for self-oscillation. Damn.

Ben

I just hook up and alligator clip jumper between pin 1 of the preamp tube and the chassis whenever I have the amp open. Also, remember to put the amp standby in "play" position.

etch wrote:Ben, when you say tidy do you mean really tight wiring, close to the chassis and in bundles near the power supply transformer? Stuff like that? Where was the oscillation coming from, the driver tube?

Just curious as I try to make my wiring look good but have had a couple of problems with a gas regulator tube (0D3) in a hi fi amp and a 5842 driver tube.

I'd love to write a book on the basics of rock and roll audio. I just don't know what I'd cover that would be new. Best I could do would be to compile the stuff into one book and then try to explain concepts more clearly for the nerdy but not totally schooled rock instrument hobbyist.

Perhaps seminars are the answer?