[Cedric01]

For the folks here that have tube amps, do you bias your own tubes or do you take it to the shop? Are Marshall JCM amps hard to bias for the average do-it-yourself person?

[Andy S]

Cedric,

I used to work for a sound company a Looong time ago. we did amp repairs and stuff as well as system installs. If you have the right test gear, it isn't too hard to do.

I would suggest you go to a site called guitarnuts2, at this address

http://guitarnuts2.proboards45.com/index.cgi

It is a forum and the guys there are pretty knowledgable on amps & stuff. They can give you some real solid advice on what to do & how to do it.

If you do the adjustment yourself, remember your messing with some pretty high voltages. be careful in there!

[allthumbs]

The most important thing to remember is that it takes 24hrs for the juice in the amp to bleed off unless you have something to bleed it off faster. Putting your hands in an amp before it is fully discharged will kill you. Be careful.

[Brian Hill]

Originally Posted by allthumbs

The most important thing to remember is that it takes 24hrs for the juice in the amp to bleed off unless you have something to bleed it off faster. Putting your hands in an amp before it is fully discharged will kill you. Be careful.

You short all the power supply filter caps to gnd. and this will discharge any stored energy.

BH

[Brian Hill]

Originally Posted by Cedric01

For the folks here that have tube amps, do you bias your own tubes or do you take it to the shop? Are Marshall JCM amps hard to bias for the average do-it-yourself person?

Like Andrew said, it's not hard with the right equip i.e. volt meter and I use special adapters that plug between the tube and the chassis that have leads that go to my meter which keeps me from having to remove chassis or cover plates to get to the circuit.

BH

[Cedric01]

Originally Posted by Brian Hill

Like Andrew said, it's not hard with the right equip i.e. volt meter and I use special adapters that plug between the tube and the chassis that have leads that go to my meter which keeps me from having to remove chassis or cover plates to get to the circuit.

BH

Where can a person pick up this special adapter?

[Brian Hill]

Originally Posted by Cedric01

Where can a person pick up this special adapter?

I made them with tube bases from old tubes and some tube sockets. Then soldered the pins to the socket lugs and soldered the test leads to the proper connection and fastened the works into a PVC coupling. You drill a small hole in the coupling for your test lead to exit a walla!! You have a test adapter!


BH

[Ultimate Garage Band]

My amps don't need biasing; I just have to purchase a matched set so I'm of no help on this one.

[Cedric01]

Thank you all for your excellent advice!