Altair 680 power supply...

Tony Duell ard at
Tue Jan 19 14:43:00 CST 2010

> > It's all good--my idea of a "voltage regulator IC" used to be a 741
> > op amp  feeding a darlington.  :)

Of course the 723 is a referece supply and an op-amp (which you can use 
to feed a darlington) ;-)

>    Hey, there you go. ;)  I'm a 2N3055 man, myself.  You can arc weld  
> with those things.

Ah yes. Good solid transistors. The PSU board of the plotter I am 
currently repairing has 5 of them on it. One for the -15V logic supply 
regulaotr, and 2 for each of the motor drivers (I would have expected an 
NPN/PNP pair here, but I guess there wasn't a suitable PNP transsitor 
available in 1959)

IIRC the 'modern' 2N3055 is actually a 2N3055H, you can't get the original
one any more. It doesn't matter for most applications, though. Either Bob
Pease or Jim Williams makes a comment in one of their books. 


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