butterguitar

All i have to say is....WOW! What a fantastic sounding tube guitar amp!!!
It sounds great out of the box, and best of all it sounds very similar to a jcm900! Fantastic 80's metal tones, no need for a tube screamer with this amp.

My only thing is, should I set the bias for this amp? I don't know how to check it (my tech used to maintence my last tube amp, but he has since moved). What is a normal bias rate? What will happen if the bias is set too low or too high?

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Bugera 1990
Crate Blue Voodoo Cab w/ Celestion 75's
Marshall AVT w/ MC412
Kramer Pacer
Epiphone SG Double Neck
OLP MM1 Guitar
1987 Yamaha Pacificia

bro blue

I have a Bugera 6260 and a 333. There are places to bias inside the amp using a voltage meter. The bias settings are available on the web. You shouldn't have to bias the amp unless you change power tubes. Remember, tube amps, even if they have been turned off and disconnected for a while, may still contain lethal voltages. Lethal as in "it will kill you dead."

T-Bird

Hi.

Congrats on the NAD.

While the bias shouldn't shift, with modern bulk tubes it will. IME for the first 20 hours or so of operation. If the tubes have been propery burned-in the bias shifts less if not...

Huge, huge + 1 for NOT to poke around in the internals of Your amp if you don't know what you're doing.

Regards
Sam

butterguitar

How do I drain the voltage from the amp before working on it?

__________________
Bugera 1990
Crate Blue Voodoo Cab w/ Celestion 75's
Marshall AVT w/ MC412
Kramer Pacer
Epiphone SG Double Neck
OLP MM1 Guitar
1987 Yamaha Pacificia

bro blue

You'll find a couple of good links here:

Tube Amp Mods - SAFETY Questions - Guitar Noise Forums

If you are just checking the bias with a voltage meter and turning the bias knob (if it is set up to adjust like mine), you shouldn't have to discharge the filter caps although it is still a good idea to do so in almost all cases. The caps should not be visable if you are just looking at the power tubes and bias adjust knob.

Here is a link to the spec sheet I use:

http://www.behringerdownload.de/_Bug...9-10_Rev.1.pdf

If you still have the stock power tubes in it the bias point should not have drifted much. They may have been over/under biased from the factory, though. If you replace the power tubes you have to replace them with a matched set, you shouldn't just pick a tube here and there.

MartyStrat54

Why do you feel the bias has drifted? You stated that the amp sounds fantastic and that to me means the bias is right where it needs to be.

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MARTY

2009 Gibson Explorer-Hell Raising Machine
1989 Fender Strat Plus USA
2008 Fender Tele USA
2004 Schecter Elite w/DiMarzio's

TSL100 with custom 4x12 cab. TSL122 with Man 'O War Speakers.
TSL602 #1 with JBL D123 Speakers and 602 #2 with Altec 417 Speakers. "Oh so sweet my friends."
DSL401 #1 with Red Fang Speaker and 401 #2 with JBL D123 Speaker.

Tubes: Let's just say they are NOS that kick ass.

TPR

Butter,
Like Bro said, you do typically want to drain the filter caps before working inside the amp. However, you can't do that when biasing because the bias reading has be taken while the amp is on. Also, before biasing you need to find out what the plate voltage is, which of course requires the amp to be on.

There's already a wealth of info about keeping safe and about how to do the biasing, so I won't go into that except to say - Don't work with both hands inside the amp! Keep one away from the amp at all times. If you have one hand on the chassis or other ground point and the other hand touches a high voltage point, it might be the last amp you ever work on.

I don't know anything about the Bugera, so the above info assumes that it has an adjustable bias that can only be accessed after opening the amp up.

By the way, if your bias is too high your tubes will burn up fast. If it's too low, your tubes will last forever, mainly because the amp will sound so bad you won't want to play it. There's a bias range, but you would need to find it by knowing the plate voltage of the amp and the max dissipation rate for the tube.

And if I haven't already worn out this post, one more thing. If you can find a tech, checking the bias should be pretty cheap. That would let you put off the learning curve for a bit. If you have to do it yourself, take your time learning so you don't get zapped or damage the amp.

Cheers.

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The awesome tone coming out of my amp almost makes up for my inability to play.

TPR

I dunno, some guys seem to like running pretty damn hot, to the point where they're burning through tubes pretty quickly. Take it a little further and I'd be worried about damaging the amp. Is that paranoid?

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The awesome tone coming out of my amp almost makes up for my inability to play.

butterguitar

Well like i said the amp sounds fine right now but I just want the amp to run at the peak performance. I got everything set up correctly now. I just gotta figure out what ohm setting to run my halfstack at lol

__________________
Bugera 1990
Crate Blue Voodoo Cab w/ Celestion 75's
Marshall AVT w/ MC412
Kramer Pacer
Epiphone SG Double Neck
OLP MM1 Guitar
1987 Yamaha Pacificia

TPR

OK, I hear you and it's probably all good, but at least make sure you aren't red plating the tubes after running the amp for awhile. It's the easiest thing in the world to check while in normal operation. Cheers.

__________________
The awesome tone coming out of my amp almost makes up for my inability to play.

LesPaulopolis

16 ohm tap on amp
high power
mono cab input
16 ohm tap on cab

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'68 RI LP Custom
JCM900 + EQ & Boost

Oze

Hey all....greetings from Downunder
I own a Bugera 1990 and there's no need for rebiasing out of the box...HOWEVER..
You CAN download a document from the Bugera website as a .pdf with step by step instructions