"Gareth Magennis"

Any kind of dodgy connection here can blow a mains fuse.


** Had a Marshall 100W head returned to me repeatedly for blowing its AC
fuse in the first few minutes of the gig - of course, it tested perfect
while on my bench, no matter what torture tests I tried.

The cause eventually turned out to be a loose fitting IEC plug that arced
under heavy vibration (when sitting on a cab) and made the AC power surge
over and over till the fuse blew. I used my own IEC lead in the workshop so
initially I never saw the fault.

In another 100W Marshall, I found that if I turned the amp off and then back
on again in 3 to 5 seconds, the inrush surge was much longer than usual and
took out the 2A slo-blo fuse.

This was due to the tube bias voltage dropping fast and recovering slowly in
the particular model, so the bias voltage was very low at switch on but the
4 x EL34 cathodes were still hot and so all drew a heavy DC current for a
couple of seconds.

Marshalls do SOOOO many ****ing weird things I could write a book on them.



..... Phil