#1
So my peavy 6505+ took a tumble in the van the other day and I noticed that one of the power tubes doesnt light up. It still sounds fine, and i've been using it at gigs without any problems.

Is this bad for the amp? Also, can I just replace one power tube without biasing the amp?
If I replace all of the tubes, will I need to bias the amp?
#2
Quote by guitarmageddon0
So my peavy 6505+ took a tumble in the van the other day and I noticed that one of the power tubes doesnt light up. It still sounds fine, and i've been using it at gigs without any problems.
Just thinking about it, you might be using half of the amp's power - two tubes out of four.

If it works you might as well leave it be, though if you really are using only 50w of power and half of the power amp you would have to plug the amp into a cab with twice the impedance stated on the amp's output.

If you are using all of the amp's power though plugging the thing into a cab with double the impedance might blow a fuse.

To be sure, I'd substitute the tubes.
Quote by guitarmageddon0
Also, can I just replace one power tube without biasing the amp?
With an amp that has a common biasing voltage you need to use matched power tubes to get a linear and symmetrical response from the power amp.

In short you can't just substitute one tube, you need a matched set.
Quote by guitarmageddon0
If I replace all of the tubes, will I need to bias the amp?
Ideally yes, but the 6505 biases power tubes so cold you may as well not re bias anything.

Plus afaik it's a bit of a pain in the ass to re bias that.
Name's Luca.

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Quote by Cajundaddy
Clue: amplifiers amplify so don't turn it on if you need quiet.
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#4
If it fell there is a possibility that the tube just became unseated and needs to be press back in, pretty common. Otherwise, pull one of the pairs (the pair with the burnt out tube) and flick the impedance switch down one notch, keep going.
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#5
^ yeah, you could do that if you don't need the full power.
Still keep a backup set around though, y' never know.
Quote by guitarmageddon0
Would I also need to change the preamp tubes if I changed the power tubes?
Not at all.

You may as well, but it's not at all mandatory.
Name's Luca.

Quote by OliOsbourne
I don't know anything about this topic, but I just clicked on this thread because of your username :O
Quote by Cajundaddy
Clue: amplifiers amplify so don't turn it on if you need quiet.
Quote by chrismendiola
I guess spambots are now capable of reading minds.