>> Yair.  It's very annoying to have a techie problem like that
>> and not have any real clues as to the answer.  Sure, I can
>> get around it easily, but the real cause of it has me stumped :-(

NP> It's a bastard I know.  I had intermittent (seemingly unrelated) problems 
NP> on a particular model electronic organ at one time. It was sending me batty 
NP> until I took guess and got a roll of automotive wire. Ran a seperate earth 
NP> lin efrom the chassis to the tab rail and all the problems disappered.
NP> Yours is worse when 3055's go up in smoke.
NP> I thought they were indestructable.

Only some.  The 3055 spec is met in several different ways - only the RCA
original appears to have the self-destruct immune behaviour pattern. 
Homotaxial base, they called it.  Could just as well have been
auto-distimmed doshes - but they didn't blow up, and just about everything
else made at that time would, given sufficient urging.

Epitaxial 3055 equivalents (but marked 3055) from almost any other
manufacturer included.  (I think Bendix did a few under licence, with the
RCA characteristic - or they may have been rebadged RCA silicon.)

NP> We used 3055's in a batch of 100w audio amps at one stage. (60V rails)
NP> One clown hooked extra speakers up to it and ran it on a 2 ohm load. The 
NP> amp just kept choofing for 2 hours until the heat was sufficient to melt 
NP> the plastic insulation washers and then it shorted out and blew the fuse.
NP> Even after all that, the 3055's were still OK !!

Yup.  About the same time, I was playing about with chopper power supplies
for telemetry in the Snowy Mountains.  3055's were new, and the epitaxial
"just as good" variety was 10% cheaper.  Our purchasing side
changed supplier without bothering to inform engineering - I wound up
hanging by my toeses from the Geehi inlet structure float well while
replacing transistors with real ones - major fun, not.

Regards,
Dave Hatch.

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