Blown mains fuse and owner thinks he replaced the HT and mains ones after
initial failure.
Amp failed in tune 5 into a gig , playing loud but normal for this amp (does
"The Who" front label make it louder?) and fuse/s blew. Next day, he has a
1970 Hiwatt L 100W Mark 4 ? M41.. serial number anyway, and according to the
owner very rare, this one should be ok when it gets 4 EL34 valves again.
One of the 2005 EL34, the getter was white so he threw it out ,
unfortunately . I'm out of contact with him for a couple of days but looks
as though the other of one of the side pair was partially white and kept
this one same make and appearance as the others in the amp, now mixed in
with his box of untested valves. Anyway in the end he robbed 2 EL34 from the
working vintage one and still blew fuse/s.
All Rs look and measure ok in the PA section. Powered up with 70 percent
mains with no output valves, only prea ones , and voltages seem right for
that mains including bias voltage. Tx resistances seem normal.
This part white EL34 , 2/3 white , 1/3 mirror Cs getter, blown heater. The
vertical rod electrically attached to p1 , G3 , but physically on the other
side of the valve electrically connected by the top "halo", electrode is
discoloured to blue compared to the other valves. No obvious cracks , I
suppose deliberately breaking it will confirm was still functional getter.
But something coming off the rod reacting with the getter while hot and not
fully converted to a white form ?
Won't be testing them and his other "spares" until tomorrow.
One 8 pin black socket (marked Made in Italy , EF ?) is discoloured to dusty
grey appearance around pins 2,3 and 6, 6? no pin in that one ?.
Trying a 2.2mm drill shank (not the cutting end) it is close sliding fit to
the old amp socket pins but slack sliding fit for the 2005 one
Measured a few EL34 pin diameters, p1 and 8
2.22, 2.31 mm
2.26,2.30
2.18,2.33
2.26,2.30

EL24 from the 1970 amp
2,41,2.41 mm
2.40, 2.46

so suspect contacts in the sockets? and loss of bias voltage ?
Retaining springs for the new version , not considered necessary in the the
old one