PDP-8/E H724 power supply and serial interface

Eric Smith eric at brouhaha.com
Mon Nov 17 20:12:02 CST 2008

Pete Turnbull wrote:
> I've taken my newly-acquired PDP-8/E apart to clean out the dust and 
> Part of the reason for not powering it up is that it's a 110V version, 
> and here in the UK my mains is 240V.  Looking at the engineering 
> drawings (on David Gesswein's site, and Highgate) for the H724 (110V) 
> and H724A (240V) supplies, I see transformer taps shown for both 
> voltages, and on the face of it, it should be very easy to convert. Just 
> a matter of moving the connections from tags 6 and 9 of the relay (or 
> "realy" as the schematic calls it :-))  Has anyone ever done this?

If the print set shows the same part number for the transformer for both
the H724 and H724A, it will be fine.  However, DEC sometimes used 
transformers in 60 Hz gear that was undersized for 50 Hz, despite the 
presence of appropriate taps for 240V mains.  IIRC, the 120V/60Hz RX01
had this issue.


More information about the cctech mailing list