6505 bias mod instructions

DestroyTheColossus

DestroyTheColossus

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Mar 18, 2008
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I've been wanting to bias mod my 6505 (not plus) and can't seem to find any instructions on how to do it. I've searched through this forum, and many others and can find plenty of threads with people explaining what a bias mod does, or anything else to do with bias mods, but not how to actually do them. I've even found a few posts that make reference to instructions they had found online, but no link to them. I've also found sites for companies that will do the mod for you, but I feel confident that I could do it myself with some help, and thereby save money.

Does anyone have a link to instructions on how to bias mod a 6505?
 
don't get me wrong, but the bias supply is the same principal for every amp.
If you know nothing about tube amps stuff but just learn about it it'll be the first thing you'll understand.
I don't have to tell you that the voltages in the amp are lethal (even though the power-cord has been unplugged already), if you can't find the bias-supply in a tubeamp and if you don't know that you just have to replace a resistor with a pot (and r)..and which one...you just don't know enough about tubeamps to do the mod yourself.

it's not a difficult thing to do or anything, but if you need a modguide for it. it's certain that you don't know enough about how a tubeamp works to do the mod yourself...take it to a tech, pay the 50$ and don't risk your life (and your amp)
 
It's definitely over my head at the moment, I will admit that. I was hoping to get instructions and help from a friend who knows more about electrical work. As far as techs go, all I had found so far were guy's online, charging a bit more than I would like to pay, and I would really rather not ship my amp. $50 is no problem if I can find someone locally.
 
DestroyTheColossus said:
It's definitely over my head at the moment, I will admit that. I was hoping to get instructions and help from a friend who knows more about electrical work. As far as techs go, all I had found so far were guy's online, charging a bit more than I would like to pay, and I would really rather not ship my amp. $50 is no problem if I can find someone locally.
Click to expand...

I'll upload a guide tomorrow if noone else will do.
I'd still strongly advice to have someone else do it.
I can't stress it often enough...even if the amp has been plugged out for some time (sometimes even days)...you touch the wrong part=you die!.
make sure to have someone around who's experienced in soldering and has worked on stuff like that before...it's a very easy mod to do takes like 10 mins), but it's also really dangerous if you don't know exactly what you're doing
 
Lasse Lammert said:
it's not a difficult thing to do or anything, but if you need a modguide for it. it's certain that you don't know enough about how a tubeamp works to do the mod yourself...take it to a tech, pay the 50$ and don't risk your life (and your amp)
Click to expand...


Just don't take it to my tech! When the 5150 combo I got off Ebay arrived with its shit pushed in, I asked him if he could include an estimate of the cost for adding a bias control pot in with his estimate for repairing the physical damage. He kept saying, "You don't need to set the bias, it's fixed." I couldn't break it down to him without resorting to "fire good, fixed bias bad" caveman talk, so I gave up and let him work on the physical problem he could already see instead of ones he would have to imagine.
 
iekobrid said:
Just don't take it to my tech! When the 5150 combo I got off Ebay arrived with its shit pushed in, I asked him if he could include an estimate of the cost for adding a bias control pot in with his estimate for repairing the physical damage. He kept saying, "You don't need to set the bias, it's fixed." I couldn't break it down to him without resorting to "fire good, fixed bias bad" caveman talk, so I gave up and let him work on the physical problem he could already see instead of ones he would have to imagine.
Click to expand...

wow!
 
sysera said:
I just kept adjusting the bias pot on my 6505+ until it sounded good to me.

lol @ you fuckers. Go write more songs.

:D
Click to expand...

True, but the range of that control is still in the cold range, as to allow the iser to adjust it, but still never go over the edge and damage the amp.

I have mine set as hot as the bias pot will allow, but IIRC it's still under 22mA's.
 
nwright said:
True, but the range of that control is still in the cold range, as to allow the iser to adjust it, but still never go over the edge and damage the amp.

I have mine set as hot as the bias pot will allow, but IIRC it's still under 22mA's.
Click to expand...

yeah, same with the JSX..even in max position it's actually still too cold and in crossover distortion range
 
nwright said:
True, but the range of that control is still in the cold range, as to allow the iser to adjust it, but still never go over the edge and damage the amp.

I have mine set as hot as the bias pot will allow, but IIRC it's still under 22mA's.
Click to expand...

Agreed, but I adjusted mine "by ear" to whatever I thought sounded best, and I didn't even end up hitting the maximum level on the pot. So I have no complaints.
 
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