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In Reply to: RE: Help w/ VTL IT 85 posted by shersta on September 16, 2009 at 18:06:50
I got a new fuse (the B+ had blown), popped it in and powered it up. The tube that had glowed bright red measured at 150 millivolts (the manual says it should read between 275 and 300). I adjusted it back into range and noticed that the reading was slowly dropping. After it dropped about 20 millivolts (it took about a half hour for this to happen), I shut it down and let it sit for a half hour. I unplugged it and swapped the tube that had glowed with one of its neighbors and started things up again. I had to adjust the bias in the swapped tubes and then noticed that the tube I had placed in the socket where the glowing tube had been was also losing voltage, though at a much slower rate (it took about 2 hrs to lose 20 millivolts).
So, it looks like I have at least one bad tube and maybe some additional damage (a resistor?). I have a new quartet of power tubes winging their way here, and I'll try this again when they arrive.
Does anyone have any additional input? And thanks for all your help so far.
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