96 Tremoverb tube issue

Hey guys, a while back I picked up a tremoverb in a trade. When I got it, I plugged in and nothing. After i looked again, I noticed that one of the 6l6 and 5u4GB tubes had been mixed up. I saw the 5U4GB was burned, So I haven't tried the amp since then, because I wanted to check it over first. Well today I pulled the chassis out and found this. Notice the resistor is fried.


So then I took a closer look at the tubes and found this. I'm not sure if you can see in the pic, but the tube is kind of black and burned.


I also noticed the both of the 5U4GB tubes are different sizes, which I doubt would be an issue but just double checking. Anyone know?


Other than the one resistor and tube, everything else looks good to go. Do you think if I swap the resistor for a new one, and get all new tubes everything will be ok?

You have a grid resistor failure. Not an unusual problem, common break down on any tube amp. A grid resistors could last a lifetime of the amp or could burn out anytime.

Get the value and try replacing it. Hopefully the burnt resistor was not cause by something else.

I had the same thing happen to my 2 channel Recto. It still works though :shock:

Do we know the value these are supposed to be?

Hopefully it's just the grid resistor. That's an easy fix. The only thing that worries me is that when I play the sound fades in and out, almost like if the tremolo was on, even though it wasn't. Here is the schematic for the TOV for the grid resistor.
http://www.classictubeamps.com/schematics/Mesa/Mesa%20Boogie%20Trem-O-Verb%20schematic.pdf

Because the rectifier is a diode and the pins do not correlate whatsoever with a 6L6GC or other pentodes, the resistor burned because the heat exceeded its wattage rating. That same condition would burn the 5U4GB. This is actually a normal thing if those tubes are swapped. A new 5U4GB and a 1k/2W resistor should have you good to go, as long as the OT isn't messed up. I hope you got a great deal in this trade, because I'm pretty sure this low cost repair gets you a great amp.

afu said:

Because the rectifier is a diode and the pins do not correlate whatsoever with a 6L6GC or other pentodes, the resistor burned because the heat exceeded its wattage rating. That same condition would burn the 5U4GB. This is actually a normal thing if those tubes are swapped. A new 5U4GB and a 1k/2W resistor should have you good to go, as long as the OT isn't messed up. I hope you got a great deal in this trade, because I'm pretty sure this low cost repair gets you a great amp.

Click to expand...

Yeah I have the parts on the way, so we will find out shortly haha. And yes I got a good deal. I traded a used 90s American Standard Strat for it, so I came out on top for sure.