PDP-8/A transformer hum

Bob Smith bobsmithofd at gmail.com
Tue Jun 9 06:48:18 CDT 2020

Is there a recommended alternative or replacement power supply for the 8/A?

On Tue, Jun 9, 2020 at 4:20 AM Marco Rauhut via cctalk
<cctalk at classiccmp.org> wrote:
> Hi Josh,
> i have restored last year a PDP-8/a to and had the same experience like you with the Powersuppy. I felt also wiered about the bang in the transformer in the moment of switching it on.
> Marco
> > Am 09.06.2020 um 09:02 schrieb Josh Dersch via cctalk <cctalk at classiccmp.org>:
> >
> > Hi all --
> >
> > I'm working on a PDP-8/A I picked up at VCF West last summer.  After a lot
> > of cleaning and some power supply repair it's showing signs of life (CPU
> > seems to be at least minimally functional, core memory is going to need
> > some debugging.)
> >
> > The transformer in the power supply is humming quite loudly, however, and
> > I'm curious if this is normal for the 8/A (or is typical for an 8/A of this
> > vintage).  I'm used to the supplies in various other DEC machines not being
> > exactly silent but this is a rather severe 60Hz buzz that you can clearly
> > hear over the fans when the machine is in operation.
> >
> > Thanks,
> > Josh

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