Hi everyone. I've read a lot of posts here, but this is my first post. I built one of the Stew Mac '59 Tweed Deluxe kits late last year, and it was working very well, but I let it sit unused for a few months while recovering from a wrist injury. Now I find that it works happily for about five minutes after powering it up, then the output volume fades to silence over the course of around 15-30 seconds, and doesn't recover until the amp has been turned off and allowed to cool down. I took a bunch of voltage measurements before and after to see what had changed (all measured at the eyelets on the tube socket/speaker output side of the eyelet board, relative to chassis ground): B+1: 392V (no change) B+2: 348V (no change) B+3: 255V before, 302V after V2B Cathode: 52V before, 62V after V2B Plate: 201V before, 240V after V2A Plate: 164V before, 196V after V2A Cathode: 1.4V before, 1.7V after V1B Plate: 132V before, 300V after V1A Plate: 134V before, 300V after V1 Cathode (pins 3 and 8 jumpered): 2.1V before, 0V after Obviously the biggest changes are around V1, with significant but smaller increases around V2. Chopsticking around the components and solder joints on the eyelet board didn't produce any audible results, but I still get the crunchy noise when touching the multimeter probe to the B+ eyelets. Do you have any tips on how to narrow down the problem? I would hardly be surprised if I have one or more solder joints that could do with some attention. I have spare 12AX7/ECC83S tubes on hand, but not a 12AY7, if I should be trying switching out the preamp tubes to see if the behaviour changes. Thanks very much.