Good Morning All,
I acknowledge this is not strickly an amp forum. But...there is some real sharp Cats about, who may be able to lend a brain-wave or two for lend.
I have a '68 Deluxe Reverb which has a Jerry modded tone stack & a D120. Love it. Here is what I know.
The only non-original part is the Power Transformer.
It is loaded with NOS tubes. Mostly RCA. The original rectifer was a Chinese Ruby.
I have read 3 Weber books, and wasted a fair amount of time checking the interwebs.
About 3 weeks ago I flipped it on. Nothing. No jewel light & no sound. As I waited I realized the Preamp tubes were glowing. Hmmm. Also, the Power tubes are not glowing. Jan RCA. They don't seem to ever glow, with one exception...see below.
Assessment Phase #1. I have AC power to the heaters, and that is what is glowing. From my studies I conclude that it's most likely a tube, and all signs point to the rectifier. I find myself a nice NOS Sylvania 5U4GB, and pop it in. Sound & jewel lamp are back! Now, I've read enough to know I need to bias this thing. So I ordered up a cool-guy bias probe. Read more stuff, and set the bias slighly to the warm side for a Deluxe. 22mA IK 428 Plate Voltage.
Oh Boy! My Deluxe is back. Wrong! Blew another Rectifier! Phuck!
Assessment Phase #2. A systems approach methodology leads me to the following points.
A) Tubes are tubes, and this old tube could've just failed. Buy new tube. Solve problem. Maybe
B) I haven't assessed the upstream & downstream systems, so I'm just as likely to blow another tube.
C) Something in the past caused the PT to fail. Could all this be related?
D) I'd also add that in the weeks that led up to the rectifier failure, I had an intermittant noise which sounded vaguely like a moth fluttering through one of the tubes. "Wha wha Wha wha"
My next thought was to dig into the filter caps. I also think it prudent to perform resistance tests on the PT. The amp appears to be recently recapped, but apparently even new caps fail. In multiple we searches, I really didn't find much on what stresses rectifier tubes. I would like to note that the Power tubes do not glow, with the exception of a faint glow on a horizontal plate near the top of one power tube. This glow seems unresponsive to changes in bias.
Thanks to All.
"Hi Ho...the Carrion Crow...FoldeRoldeRiddle"