The PDP11/04 has landed..

Henk Gooijen henk.gooijen at
Mon Feb 8 08:51:16 CST 2016

> > -----Original Message-----
> > From: cctech [mailto:cctech-bounces at] On Behalf Of Jos
> > Dreesen
> > Sent: 07 February 2016 17:55
> > To: classiccmp at
> > Subject: The PDP11/04 has landed..
> >
> > Yesterday I picked up the PDP11/04 that Jay mentioned a few days ago.
> > Less than 15 miles from home  !

On Sun, Feb 7, 2016 at 1:24 PM, Robert Jarratt <robert.jarratt at>
> I have one of these on my restoration list. I know the PSU does not work,
> and that others have tried to fix it before me, who probably know PSUs 
> much
> better than I do. It has core memory so I really would like to get his one
> fixed. I have never seen a PSU for it come available in the UK or Europe,
> so it looks like it won't be an easy job. :-(
> Regards
> Rob

-----Oorspronkelijk bericht----- 
From: Pete Lancashire
Sent: Monday, February 08, 2016 2:20 PM
To: General Discussion: On-Topic Posts
Cc: classiccmp at ; jdr_use at
Subject: Re: The PDP11/04 has landed..

Until one can restore the original power supply, it is pretty easy to
substitute a modern supply, good quality used commercial grade switchers
with remote sensing can but put on a rack shelf. But if you take that
route, be very very careful of Chinese supplies.

great catch!  And so close to home ... you're very lucky ;-)

the PSU of the 11/04 has a big transformer in the primary. Secondary
is just 24-30 VAC. The "bricks" are not overwhelming complicated.
They all have the 24 VAC as input which is rectified by a bridge and
followed by a big capacitor. There is also a fuse. A first check would
be these 3 components. Then the uA723 (or LM723) regulator ...
Only the +15V (or is it the -15V?) needs the - (or +) 15V besides
the 24VAC input.

although you could use a "modern power supply", nothing beats
the original stuff. Also you need some some components to
generate the AC LO and DC LO signals. The 11/04 needs them.

- Henk 

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