I play a Reverend Brad Houser 5 string into an Ampeg SVT-CL/Ampeg SVT-410-HLF cab, gig 4 hours twice a week. Had the amp for several years and, although I am not a tech, I have had to learn to work on it a bit. This is what happened: Amp went in to fault mode during gig (blinking red/green light on front panel). Powered up fine but when turning on the standby switch, made a pop and went to fault mode. Noticed one tube in particular was making a bright blue flash at the same time as pop. Replaced that tube (there was a small crack where the retainers ride on the glass) with an old mismatch I had. Amp worked after that, although unable to bias (one light red only, no green). I pulled the power tube board and checked the screen grid resistors as they have blown before. One was out and I replaced it (with a 220 ohm, 1/4 watt resistor). When turned on the power switch, I got the red light as usual but when I turned on the standby switch, the whole amp shut down and it won't power up at all now. I am confident in the work I performed but don't know how to proceed.