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| Guitar Tech This is the place to ask your questions about guitar maintenance and basic guitar repairs. |
May 20th, 2006
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Playing guitar for over 10 years.
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Join Date: Apr 2006
Last Online: July 22nd, 2008 05:28 PM
Location: Canada
Posts: 258
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Tube Biasing
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?
"The seeds of our destiny are nurtured by the roots of our past." - Master Po
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May 20th, 2006
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Full Member
Playing guitar for what seems like forever.
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Join Date: Nov 2005
Last Online: 1 Day Ago 10:23 PM
Location: Cincinnati, OH
Posts: 660
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Tube Biasing
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!
Andy S.
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May 21st, 2006
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Moderator
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Join Date: Feb 2005
Last Online: 1 Hour Ago 11:33 AM
Location: ont.can
Posts: 14,401
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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.
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May 21st, 2006
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Newcomer
Playing guitar for what seems like forever.
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Join Date: May 2006
Last Online: May 26th, 2006 10:28 PM
Location: USA
Posts: 28
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Quote:
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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.
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You short all the power supply filter caps to gnd. and this will discharge any stored energy.
BH
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May 21st, 2006
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Newcomer
Playing guitar for what seems like forever.
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Join Date: May 2006
Last Online: May 26th, 2006 10:28 PM
Location: USA
Posts: 28
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Quote:
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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?
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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
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May 21st, 2006
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Member
Playing guitar for over 10 years.
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Join Date: Apr 2006
Last Online: July 22nd, 2008 05:28 PM
Location: Canada
Posts: 258
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Quote:
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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
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Where can a person pick up this special adapter?
"The seeds of our destiny are nurtured by the roots of our past." - Master Po
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May 21st, 2006
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Newcomer
Playing guitar for what seems like forever.
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Join Date: May 2006
Last Online: May 26th, 2006 10:28 PM
Location: USA
Posts: 28
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Quote:
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Originally Posted by Cedric01
Where can a person pick up this special adapter?
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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
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May 21st, 2006
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Moderator
Playing guitar for what seems like forever.
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Join Date: Jul 2005
Last Online: January 23rd, 2008 08:22 AM
Location: Columbus, GA
Posts: 595
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My amps don't need biasing; I just have to purchase a matched set so I'm of no help on this one.
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May 21st, 2006
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Member
Playing guitar for over 10 years.
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Join Date: Apr 2006
Last Online: July 22nd, 2008 05:28 PM
Location: Canada
Posts: 258
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Thank you all for your excellent advice!
"The seeds of our destiny are nurtured by the roots of our past." - Master Po
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