If the caps are bad then you will lose bias voltage ( they are shorting to the outside can and ground). Read the voltage on the terminal, if it is more than 2 or 3% off/under, they are weak or failing. You need to read your bias right before the 220k resistor if there are no tubes in the amp. With tubes in, no signal, you need to be very close to the spec since you are fixed bias.
As for the other items about the screen....it also pulls current and if those screen resistors are off they need to be replaced. If the screens were electrically damaged, then you now have hot spots which can make those plates glow again as soon as some stress is on them...meaning playing. Use them to do your testing, with no load/signal, they should be ok to atleast determine/fix the voltage issue...after than pitch them.
As for the other items about the screen....it also pulls current and if those screen resistors are off they need to be replaced. If the screens were electrically damaged, then you now have hot spots which can make those plates glow again as soon as some stress is on them...meaning playing. Use them to do your testing, with no load/signal, they should be ok to atleast determine/fix the voltage issue...after than pitch them.
Mouser, Newark, DigiKey, Partsexpress....common values, cheap prices, superior parts. Big cans: CE Distributors, tubesandmore, Triode in Chicago.
If you ahve a bunch of old carbon resistors, replace them with Vishay or Panasonic. You need to check them all...and do it by unsoldering one end not measuring across it in circuit. If they have bands of color and you don't know the colors, google resistor color code.
Brian, Who we let use part of the back room for his backline business had a similar (not the same) amp with glowing output tubes. Took it to the local music store who looked at it and sold him new tubes and "adjusted the bias." The amp worked for the first set and then blew the fuse.
I took a look at it. The power transformer was fried. That is what happens when you run an amp with red tubes for too long. The transformer wholesale was over $100. After replacing it I found the bias was well out of range. The cause, a shorted filter cap in the bias circuit. The cost of the cap under $1.
So replace both caps, get new resistors and replace all of them. The cost of all the new parts will be less than the UPS charges! Not doing it will be way more expensive!
I don't think it is the grid caps as you say both tubes overload and I don't think a single cap could do that. (Could be wrong.)
Then you just might want to get better 6L6's than the junk you have in there.
I took a look at it. The power transformer was fried. That is what happens when you run an amp with red tubes for too long. The transformer wholesale was over $100. After replacing it I found the bias was well out of range. The cause, a shorted filter cap in the bias circuit. The cost of the cap under $1.
So replace both caps, get new resistors and replace all of them. The cost of all the new parts will be less than the UPS charges! Not doing it will be way more expensive!
I don't think it is the grid caps as you say both tubes overload and I don't think a single cap could do that. (Could be wrong.)
Then you just might want to get better 6L6's than the junk you have in there.
This is a Fender amp we are talking about.....
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