[Paul Dorman]

On 1/15/2021 8:40 AM, Mike Rivers wrote:
On 1/15/2021 6:43 AM, Chris K-Man wrote:
It was the main AC fuse F1, a 2.5 Amp Slow-Blow fuse, that was blown
open.

Then I noticed the single 12" 8 Ohm speaker, was incorrectly hooked
up to the 16 Ohm output. Was this possibly the cause of the blown
fuse?

Highly unlikely, but you should connect the speaker to the 8 Ohm output
and then figure out why the fuse blew.

Did you replace the fuse and the replacement blew either instantly or in
a short time? If so, figure out what's causing it. It could be a shorted
diode in the power supply, a short in the power transformer, or
something in the amplifier circuitry drawing too much current.

If this was a one-off blown fuse, you replaced it, and it hasn't blown
yet, then just play on.


Ok, I replaced the fuse, with no tubes installed, and
no speaker load, and I am reading a good +518 VDC, on at least
one pin, for all the tubes. And I also found a +274 VDC pad,
which I believe is connected to the +290 Volt "D" line.

The fuse is holding. My guess is perhaps there was a bad
tube, which blew out the fuse initially, and then tubes were
taken from this amp, because no one bothered to replace the fuse.