PDP-8/A transformer hum

Marco Rauhut marco at familie-rauhut.eu
Tue Jun 9 03:09:15 CDT 2020

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.


> 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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