On Tue, 24 May 2011 11:42:05 +0100, N_Cook wrote:

Amp used for the first time, in 2 years of regular mains use, with a
generator. Works fine with no problems. Coincidence ?, next gig back to
usual mains supply, at power up, blows the mains fuse. The GZ34 is
failed both sides, 0 percent output . Inspecting the fuse it has failed
at an end , not the central (T) section and otherwise complete wire
shows no sag or discolouration. So possibly mechanical failure of fuse.
If fast make/break intermittant action of the fuse wire at an end ,
would that knock out an RR valve? What in general happens in the failure
of RRs ? I've only ever seen 75 percent , same as new, or 0 percent
"goodness" at prescribed current settings of the Avo valve tester.

If I pop a new valve back in, take some measurements and all seem
respectable, I don't try to dive further in and create scenarios in my
head as to the failure mode. UNLESS it comes back a few hours of usage
later with the same failure. However, after it is placed in a cabinet
I stress test all amps into a non-reactive 300 wrms 8 ohm resistor, one
of two I have mounted on a large heat sink from a CNC power supply. I use
a 400 hz tone and monitor the output adjusting the output until I see
just a taste of crossover distortion. I leave it this way until I can
smell and feel the amplifier/ output transformer, choke, mains
transformer etc get more hot than under normal use. Then it's tested
with a guitar and cabinet if it's just a head. I'm a musician so I have
those things laying around. I usually use my 4x12 Peavey cabinet for
amps that aren't combos. And a Fender 4x10 for Bass. I know what the
instruments should sound like though both cabinets with good amps.



--
Live Fast Die Young, Leave A Pretty Corpse