[TenTec] 252MO PS Hum

[Stuart Rohre]

On older power supplies, sometimes the laminations of the power transformer
work loose.  Check the four bolts holding the power transformer together,
and tighten those and then see what is the noise.  Also check the bolts
mounting the transformer to the chassis.  You might try setting the power
supply on a typewriter pad, or other damping material to keep any hum from
being magnified by the desk surface.  Cork coasters under the feet might
help, as well in lieu of a pad.
73,
Stuart K5KVH