Otari MX5050 2T right channel no signal

[Shelby 412]

I just picked up an Otari MX5050 1/4" half track machine. The problem is no signal passes at all on the RIGHT channel. Nothing in and nothing out. Also when I press the Test OSC button, it only generates a signal tone on the LEFT channel, and only the LEFT VU meter moves, no movement on the RIGHT VU meter.

What could be some of the causes? I'm not a tech, but I have some ability to be a home techy. Trying to determine if I can fix this with some cleaning or mild soldering? Or if it needs to go to the shop.

TIA

[Shelby 412]

Update

I got the machine to play both channels by cleaning the FT/2T PB head switch!

Also I tried cleaning the input XLR jacks but still no input signal into the RIGHT channel

So the focus is now on - no input signal to the RIGHT channel 2

[Listens2tubes]

Try cleaning the internal speed (L-H on the main board) as well. I have solved many problems just by cleaning that switch.