TH30 Blowing HT Fuse with tubes out

[HaroldBrooks]

Cool

Just in case check wiring with a loupe or high power reading glasses (I use +4 ones for that) and under good light.

Often itīs not a "parts" problem but "something else".

You might have a solder drop touching what it shouldnīt, a nut/washer/whatever pinching wire insulation (that burnt me many times) , insulation paper/film crushed and shorting what it should insulate, etc.

Thatīs why shotgunning *everything* may still not solve a problem

True statements Mr. JM Fahey, shorts come in many shapes and sizes, and some are found outside the normal suspects including tubes, caps, transformers, etc...

I had a cloth covered wire for the power tube filaments grounding to the tube socket on a very old Valco amp. I amp had no volume and I noticed the filaments were dim, so I checked the heater voltage and found it super low, and when I wiggled the tubes the problem went away intermittently ! I'm proud of finding that one so quickly (under 30 minutes for the diagnosis and final fix), but to be honest I probably caused the issue by swapping too many power tubes back and forth in that amp, along with the frayed and much too close to ground wire the amp had to begin with. Never blew a fuse during all that, but that was next up for sure given the short was present.

[J M Fahey]

Oh, but cloth covered wire has so much MOJO!!!