i have a hum problem with a reel-to-reel machine i bought recently. it's a uher report monitor (model 4000
) from the 70s' which is in very good cosmetic conditions.
actually the problem doesn't occur every time i use the tape machine but when it does, something in the circuitry picks up 50hz (+higher harmonics) to produce a loud hum that covers most the recorded signal. the hum is often not constant but fluctuates in intensity.
i thought the problem was linked to my setup and/or the physical location of the tape machine in a room. i also suspected the cheap DC wallwart but very recently i bought the exact same machine because the first one was so unreliable and used the same DC converter and this time no hum noise! so that pretty much eliminates the walmart, setup and physical location possibilities and tells me there's something wrong in the tape machine's circuitry.
i'm not quite sure how to solve this problem and maybe something similar happened to some of you in the past.
any help would be much appreciated