Tape Eros trouble

[xcortes]

That's why I left the whole town without energy!

The switch is the same as the one used on the Quickie as a a source selector, right? I have one of those to try.

[Doc B.]

Yeah, that's the same switch. Try wiggling the STP cables that connect the switch to the terminals too. Maybe there is a loss of continuity or short inside one of them.

[xcortes]

New switch and new STP cables going to the switch. Extreme care taken in connecting these. Same old buzz :>(

[Doc B.]

Hmm, is the problem maybe at the input jack?

[xcortes]

Changed the input jack and the STP coming out of it.

No improvement.

Would you accept me to your annual debug day

[xcortes]

An additional piece of information.

Remember I first said hum was on both channels and the said left channel only?

I was right both times. When connected to the tape heads I get hum on both channels. When inputs are shorted hum comes only from one channel. When not hum comes from both channels. The noise is not picked up by the heads or the wire because the Repro is silent with the same deck in the same position.

There's a very slight reduction in hum if I connect the ground post to the deck but almost insignificant.

At this time I'm almost sure I have a ground loop.