"Pooh Bear"
Not Crest by any chance ? Those 2r2s IIRC ?
** No.
The amps were the Jands J1000 and J700 (Australian designed & made).
The Motorola and later "Hi-Rel" output BJTs base pins were fed via 10 ohm
0.25 watt resistors.
At high output currents (or under short cct tests), the drop across each 10
ohm was between 0.4 and 0.9 volts !!!
To add to the insanity - the 0.47 ohm, ballast resistors were on a separate
PCB that attached to the one with the BJTs via multipin plugs and sockets -
with the result that the extra copper track lengths altered the actual value
of the ballast by up to 30 % for the ones at the end.
On test, under load - the Ic variation across the 10 BJTs had a ratio of
typically of 2:1 !!!
In a desperate attempt to solve the high resulting *blow up rate* in the
field - Jands went from Motorola MJ15024/25s to the more expensive Hi-Rel
EB204 / ED 204 devices. The Hi-Rels had a much tighter spec for Hfe and Vbe,
so gross mismatching was reduced.
All Jands really had to do was remove all those damn 10 ohm resistors and
run a solder coating along the long thin tracks that fed the distant ballast
resistors.
Done this many times when carrying out repairs:
Voila - near perfect Ic matching.
There were a whole BUNCH of other mindless stuff ups too - like speaker
DC protection relays that didn't.
Cost Jands' reputation very dearly.
They're actually there to stop VHF oscillation ( a la mosfet ).
** I very much doubt that it is VHF.
HF maybe ?
Fusible types are they ??
......... Phil