Replacing failed powersupplies on qbus PDP-11s

Tony Duell ard at
Sat Jan 31 12:51:37 CST 2009

> On 30 Jan 2009 at 16:41, Roy J. Tellason wrote:
> > Eh?  Why would it do that?
> Read about it:
> Interestingly, the real-world example cited is the addition of an=20
> input filter to a PDP 11/40...

Which would be curious if true, since no standard PDP11/40 used an SMPSU. 
Switching _regulators_, sure, but the PSU starts with a large 
mains-frequency transofrmer, which is not going to have much of an HF 

Howev,er I read the article as that the author had run some simulation 
software on an 11/40 to study the preformace of another PSU. And that 
makes a lot mroe sense.


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