PDP-8/A transformer hum

Related question: Is there any reason, other than historical accuracy and cost, to not replace the power supplies in vintage computers with modern switching power supplies?

-- Anders Nelson On Tue, Jun 9, 2020 at 10:19 AM Paul Koning via cctalk < cctalk at classiccmp.org> wrote: > > >> On Jun 9, 2020, at 2:59 AM, Josh Dersch via cctalk < > cctalk at classiccmp.org> wrote: >> >> 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. > > Assuming these are traditional transformers with laminated sheet iron > cores, check if the rivets or screws holding the laminations together are > loose. If yes, tighten or replace the fastener. > > paul > >