Old DEC Power Control 861C

Tony Duell ard at p850ug1.demon.co.uk
Sun Dec 20 12:50:11 CST 2009

> Tony Duell wrote:
> > The DEC power cotnrollers are _very_ simple inside, and you don't really 
> > need tjhe printsets to repair them.
> >   
> You need the print set of a DEC power control if you're trying to figure 
> out why the power control in a Type 30 point-plot display attached to a 
> PDP-1 keeps tripping its circuit breaker as soon as mains voltage is 
> applied to its input.  Once you have the print set, it becomes apparent 

Well, OK, if the Phantom (as the Radiophile magazine calls him) or that 
well-know UK radio amateur M0RON has been in there before you then all 
bets are off. 

> that someone seriously miswired the innards of the power control, 
> possibly in a previous misguided repair attempt.  Upon rewiring it to 
> factory spec, and replacing a switch on the front of the power control 
> that turned into a dead short when it was miswired, it will then work 
> properly.

However, I suspect in this case I could have got it doing the right 
things without a printset. Not necessarily the original DEC circuit, but 
at least not shorting out the mains. 


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