I’ve got a bit of an odd one. I know this is similar to an ongoing thread, but there are enough differences that I think it warrants it’s own question.
I live in a 230/240V country (at the bottom of the world) and have purchased a used (I know I know) PS-2 (not A) that was made for the Japan market (100V).
The seller gave be a step down transformer he was using with it.
When I use the unit in silent mode, I couldn’t be happier.
When I throw that Operate switch though, it immediately starts humming like there is no tomorrow, both chasis and through the speaker.
I’ve since determined that maybe running it at 110V (the step-down) may be causing some of the issue, so was happy to hear a GREATLY reduced, if not gone, hum when running on my variac at 90-95V.
Now comes the fun part.
After I reduced the hum, I’m hearing a radio station through the speaker. It’s a foreign language, likely eastern Asian based on the language I can hear and the style of music I’m hearing.
I replicated with the step-down xfmr and the station is still there, but it’s much harder to hear over the massive hum.
I have video/audio of it all.
I’m guessing the very least I need to do for the hum is a better step-down, or different power xfmr for the unit, but would love some advice on that.
And I have no fkn idea on the radio station, so I’m all ears for suggestions there.
Wow … radio…
Something is behaving like an antenna, do you have a very long speaker cable? But this could be related to the additional transformer and cabling. I guess this is an AM radio station being picked-up?
An AM receiver circuit is amazing simple, a few low values inductors and capacitors and a diode, so in range of parasitic parameters of tubes, especially if one of the tubes is in cut off and acting like a rectifier.
The point being that something sounds very wrong with your power station’s power amp. It could be the way you are powering it? Or it could be the unit needs a service and they can put in transformer for your region (PS 
here: 240V and BS 1363 for the win).
Sure, post the videos, that would be really useful I think.
Regards,
Dan
PS. I mean that, noise is getting into your unit somehow: either via an input or the power.