Marshall w/ 6L6GCs- Damaged?

[Subvamp]

Hey folks!
I picked up a Marshall JCM800 off of Ebay. (yeah, I know...)It showed up saturday and I gave it the once-over, and noticed the guy had 2 mismatched 6L6GCs in there instead of the EL43s. Is it possible that this guy screwed the amp up by putting in the incorrect tubes? (I seriously doubt the guy had it rebiased for the 6L6s...)Any input would be greatly appreciated.
Thanks!

[Shamgar]

Re: Marshall w/ 6L6GCs- Damaged?

I don't know how it works with Marshall amps, but I looked on the site of Koch amps and they said the following about changing tubes without Rebiasing: (I hope it helps you a bit)

Question: What will happen if I just replace the tubes without rebiasing my amp?

Answer: The are 3 possible situations that may occur:

1. The existing setting in your amp accidentally matches the operating point of the tubes and everything will function as it should.
2. The existing setting is too low. Now the idle current in the tubes will be too low which will result in an ugly sounding distortion on your clean channel. The whole amp will sound thin and squashed.
3. The existing setting is too high. Now the idle current is too high, resulting in an extra fast wear-out of the tubes and a dull sounding amp. In extreme circumstances the tubes can get overloaded.

TIP: Overloaded tubes can be recognized in general by a red glow of the grey metal plate about midway inside the tube. If you see this, switch off the amp immediately !!! (a blue glow is normal).

[Subvamp]

Re: Marshall w/ 6L6GCs- Damaged?

It does sound extremly thin, so I'll just replace the tubes and have it rebiased. Just wanted to make sure it wasn't wrecked!
Thanks dude!

[Shamgar]

Re: Marshall w/ 6L6GCs- Damaged?

no problem [img]images/icons/smile.gif[/img] I happened to read it myself a few days ago.