meiklejohn Posted August 12, 2014 Report Share Posted August 12, 2014 Hey, so I bought a jcm900 last week, although I don't really like it... until I can swap it or sell it I'm gonna have to make it work so...When I played the first time with it I noticed it was quite quiet, it's a 100watt head so it certainly shouldn't be quiet so I'm putting it all down to tubes needing changed? Here's my questions;Do I need to change all the tubes at once or just the bad one(s)? Do I have to buy the exact same tubes that are in it now?Bias... Don't know what it is but will I need to get it done?Any info you lot can give me would be appreciated. Complicated shit!Thanks Quote Link to comment Share on other sites More sharing options...
James Broonbreed Posted August 13, 2014 Report Share Posted August 13, 2014 If it's the one from Bill, did you check the power attenuator knobs on the back were turned up? Quote Link to comment Share on other sites More sharing options...
meiklejohn Posted August 13, 2014 Author Report Share Posted August 13, 2014 It's the one from Bill yeah, I can't even remember seeing that? Do you mean the 50 watt cut switch? Quote Link to comment Share on other sites More sharing options...
James Broonbreed Posted August 13, 2014 Report Share Posted August 13, 2014 Hang on.... I'm speaking shite. I bought a JCM900 from Bill and then sold it on Ebay. I very much doubt it's the same amp. It's maybe worth having a look for any retro fitted knobs on the back though and give them a damn good fiddle. Quote Link to comment Share on other sites More sharing options...
Steviepearce Posted August 13, 2014 Report Share Posted August 13, 2014 But as bigsby said there be voltages running through the head even when not powered up as it be stored. But generally you would change all the tubes so they all have the same life (yet some may blow before others even when brand new) you don't have to have the same brand but the same type of tube yes, unless it is set to be able to change tube types. My head currently has a set up where it has different brands best for doing certain jobs. You will need to bias it to get the best out of the tubes, if running too hot then it can work the tubes to hard, but if set too low then not getting the optimum performance out of the tubes. Get a matched set, at least you know the tubes be set the same (again depends on quality control)But if you don't know what your doing then don't throw your hands in there. I've always done my tubes and biasing but always used electronics and feel comfortable doing it. Quote Link to comment Share on other sites More sharing options...
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