[quote author=Ran Talbott link=topic=57529.msg414397#msg414397 date=1302029454]
One of the tubes looks black inside - does this mean its likely to be dead?
Yeah, but not necessarily: it might be the "getter", a coating put on the inside of tubes to absorb the last vestige of oxygen because the manufacturing process didn't produce an absolutely perfect vacuum.
However, my recollection (possibly flawed, because it's been about 40 years since I did anything with tubes) is that the coatings I saw usually looked more silvery. So the black is probably a deposit of the magic smoke, but you could be lucky.
I'm pretty sure you're right, Ran; getter coating are more "silvery" (I liken them more to the color of lead, though). Then again, I only base this on what I have seen myself, and what I have read - I know little to nothing more about tube electronics. I myself have an old Zenith tube radio that needs work; one of these days I intend to make a list of the tube numbers and see what I can dig up at Apache Reclamation and elsewhere (I broke my own rule I posted above before I found you shouldn't do it - I plugged it in - no fire or smoke, though - just 60 Hz hum thru the speaker; at least the amplifier portion is likely good, but the RF seems shot in some manner).
BTW - have you looked up tube testers on Ebay lately? At one time you couldn't give them away; nowadays they're fetching amazing prices - I was trying to find a good one a couple of weeks ago, and couldn't believe what I was seeing, price-wise. Must be all the guitar and audio tube-amplifier fanatics out there...