Big Bottled Rocket farting out

[passfan]

I've built the second one of RJ's rockster reverbs with a farting distortion at full volume. Sounds nice until 2 to 3 o'clock and then farts out. B+ is around 350 with 51 ma on the plates. The first one had a B+ of 400 or so. I used a scarfed output transformer from an old heathkit stereo amp. It is an old Stancor that was running a pair of 7591's. the first one had an Edcor and it seemed a tad louder. This amp seems bassy for some reason and the first one had a Brits switch while this one does not. I'm down to swapping out the OT for a beefier unit thinking this one may be either too small or have a winding problem. If you stand too close with a guitar the hum increases more than the usual. I also installed the heater wires last ala dumble style , up in the air while keeping everything else down on the deck

[Structo]

What value grid stoppers do you have on the power tube grids?

[passfan]

1.5k with 1 k screens and .1 through the PI to the output tubes

[Roe]

1.5k with 1 k screens and .1 through the PI to the output tubes

try something like 10k, 1k, 0.022u respectively

[passfan]

Well I found it , after doing a host of things all week long including OT replacement and stripping the reverb parts completely out (burned up the dropping resistor for the driver supply). It turned out to be a bad triode in V2. I thought it odd, at some point during the week, when I swapped out a 12au7 in V2 my gain didnt change....doh. It had me frazzled

[keewee]

v2 is the source follower I believe. This can be a problem with some newer 12ax7 tubes. Check the max cathode voltage rating for the tube you plan on using and check it with your volt meter in circuit you may have to increase the cathode resistor to say 100k. 12au7 tubes have a higher cathode vkmax rating.