If the amp is in standby, then the B+ is not going through the circuit past the standby switch, so your wiring may still be suspect. If the problem occurs as soon as the standby is moved to the operate position, then you have to look at what occurs when that happens. Suddenly a surge of high voltage goes through your circuitry, and because the tubes are in the amp along with the rectifier, then there is a large current draw too that your power supply and caps have to supply to the circuitry. If you have a defective power tube, rectifier tube or incorrect wiring, then you will have a problem with the fuse blowing when the current draw for that part of the circuit is exceeded. Testing without the tubes will verify if you have a wiring problem or not. If it works without tubes, then try the rectifier and see if it works that way. If it doesn't then having a solid state module that you can try will show if your rectifier tube is a problem or not. Regardless, the first time an amp is fired up, it should be on a current limiter and should be run without tubes to verify that there is not a problem. This way you don't blow through a ton of fuses to try to find the problem. Once you've verified that it works without tubes, then you know your circuitry is correct and you can proceed step by step to find the problem as I mentioned. A solid state rectifier would work fine with your amp the way it is now. Adding limiting resistors might help, but it is not your problem. Try the tests.....
Greg
