Please HELP!!! DC-10 Power Failure - BLUE TUBES Question

[Charlie Boo]

After years of reliable service, my DC-10 just crapped out on me while I was practicing. Just a quick clicking noise, then the power shut off. Based on my limited tube amp knowledge, I assume that the first place I should start is by replacing the fuse. However, I have the following questions:

1) If I replace the fuse and it powers up fine, I should probably be concerned about what caused the fuse to blow to begin with. Can a bad power tube cause the fuse to blow?

2) I have NEVER replaced the pre-amp tubes. Could they ever be the cause of a fuse giving out?

3) Now here's the weird question - my tubes (all 4) have been glowing mostly BLUE for as long as I can remember. I know that most tube amps glow yellow/orange. What could cause this? Are they blown? Is it possible that a previous owner changed the hard-wired biasing, and if so, could that cause the tubes to glow blue, now that the regulated Mesa tubes are in there? Does this mean that my tubes have been bad for a very long time, and it finally has caused the fuse to quit?

ANy help or assistance would be appreciated..

THANKS!!!

 

[stokes]

1) Yes and yes
2)Not likely that the preamp tubes are the problem
3)The blue glow is normal.The tubes shouldnt "glow" yellow or orange,there should be a small "point of orange light" visible at the top or bottom of the plate (large grayish structure inside) but it should not be a general "glow" or a large orange/red blotch on the plate itself,that would definately cause the fuse to blow,and could eventually cause other problems.It is very likely that the power tubes caused the fuse to blow,but without seeing the amp and testing no one can say 100%,but it is a very likely scenario.If the tubes are old,I would suggest replacing them along with the fuse.If you just change the fuse,it may seem to be okay,but when the tubes get cooking it could blow again.The tubes may not be completely dead but when they start working hard they could be drawing too much current and blow the fuse.In that case they will fry sooner than later.If you dont want to take the amp to somebody,its a good idea to get new power tubes and try that first.