Superlite TMB blown fuse during voltage reading.

[MartinL]

Hello, newbie builder here, repurposing an old mojotone tmb kit into a superlite tmb. I got the amp booted up and sounding great and successfully measured voltages a couple times this morning. I was doing one last run through the voltage test sheet and I must have made a mistake and blown the fuse somehow. I had gone through all the DC voltage on the tubes and filter caps without issue, and then when checking the ac voltages at the rectifier input the fuse blew and amp lost power. Did I make a big no-no by measuring the AC voltages at the solid state rectifier input with the standby switch set to on? I'm following the Rob-Robinette startup guide, and I was able to measure the ac voltage on my initial testing without the tubes and standby switch set to off (Wire-to-ground, per his recommendation), but didn't see it stated anywhere that it would be bad to take that measurement with the standby switch on. I was just running through a new test sheet, filling it out as I went, and those HV taps were at the bottom of the page so I figured why not check them again, and shortly after probing the rectifier input I lost power. There wasn't any visible smoke, sparks, or a bad smell, but as soon as I saw the power light go off I instantly turned off the amp and unplugged it. So, was it measuring that Rectifier input that blew my fuse? If so, is there anything else I should be wary of when the new fuse gets here? I'm worried this was a foolish mistake that might have damaged the pt or something else.

[Piamp]

Your probe slipped and you made a shortcut
Change the fuse, power on the amp, it should be on!