PDP-8/M power supply questions

[Paul Anderson]

I think the regulator is a 54-09728 or 54-09827, and they were used ia lot
of DEC items.

Paul

On Mon, Apr 6, 2009 at 3:59 PM, Tobias Russell <toby at coreware.co.uk> wrote:

> Thanks Tony,
>
> Yes pretty sure its a bridge rectifier as I found H740 schematics plus
> opened up my other 8-M which I now realise has essentially the same
> power supply. I guess DEC just made slight design revisions plus
> reposition the supply in order to solve the unreliability of these
> earlier units.
>
> Studying the schematic further I've found NSS-3514 annotated next to the
> rectifier (sorry missed this when I first looked through it) so I'll see
> if I can hunt down this part. If not I'll try the diode approach
>
> Thanks,
> Toby
>
> On Mon, 2009-04-06 at 21:00 +0100, Tony Duell wrote:
> > > One is a DEC 1110714 bridge rectifier and the other is a MJ900
> > > transistor. I think I've sourced the MJ900 but can't find anywhere
> > > stocking the 1110714.
> > >
> > > Does anyone know an alternative non-DEC part number for the rectifier?
> >
> > Are you sure it's a _bridge_ rectifier? I thought you said it was a TO3
> > can, DEC often used a double-diode in that case (common cathode to the
> > case, anode to the 2 pins -- sort of a semiconductor version of an EZ80
> > :-)) as a biphase full-wave rectifier with a centre-tapped transformer
> > winding.
> >
> > In any case it should be fairly easy to get some diodes with sufficient
> > forward courrent capacity (and enough PIV -- rememebr this is _twice_ the
> > peak voltag from the transformer!) to do the job and just wire them up
> > appropritately. There should be enough spave in a PDP8/M PSU to fit them
> > in. It may not look original, but it'll get the machine going and you can
> > always fit the original part if you find one.
> >
> > -tony
> >
>
>
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