This throb noise is due to loading of the HT which goes up and down with
tremolo speed and depth. With EL84s in and all 12AX7 pulled the throb is
still there, no signal throughput of course, even makes the standyby LED dim
in sympathy when at the deepest depth. Only stops if I disconnect the ribbon
that goes to the tremolo pots to kill the tremolo oscillator
Leaving, likely ,just a JRC 2147D high voltage dual op-amp (+/- 28V not
300V) and a 2SC2910 associated with the tremolo area and something marked
SiLN D25D or SiLN D250 a 3 pin TO92 device, the S being the Nazi SS
lightning flash S.
Anyone recognise the Logo ?
Whatever this is thyristor ? is connected via 220K to the HT line.
I thought tremolo just bent the frequencies in a cyclic fashion, not
modulating the HT.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/