I picked up my first RTR a few days ago an Otari mx5050 bII
I grabbed it for very cheap as it was advertised as "requires repairs" as i was after a project to see if I could get this up and running again. I checked it out and it looked complete - I got it home powered it up and only the capstan was spinning - so I replaced all fuses and now it appears all transport controls work, all reels spin and the breaks/solenoids work fine. So far so good. I also deoxit all switches and connections.
The next issue is that the meters peg as soon as I turn it on and there is a constant hum on the headphone output - I have yet to plug anything into it other than power and headphones. The hum doesn't change at all when I turn any input or output knobs, and I can't hear the test tones or any kind of change when I switch the monitoring switches etc.
I measured DC across all Pins on the inputs and outputs and came up with some interesting results
Both Line Outputs
Pin 1: 10mv
Pin 2: 1v
Pin 3: 3v
Both Mic Inputs
Pin 1: 16v
Pin 2: 10mv
Pin 3: 500mv
Both Line Inputs
Pin 1: 1.2v
Pin 2: 10mv
Pin 3: 1.2v
My main concern is 16v on Pin 1 of the Mic inputs - this doesn't seem right, or maybe this is expected? At this point I don't want to plug anything into the inputs or outputs as I appears something is wrong.
As it is occurring consistently across left and right channels I guess I have to focus on the power supply - is there any common points I should check? I'm going to check the voltage rails and see that they are consistent.