Warning: Long-winded SS noob technical assistance request

My Centaur has a rather loud 60 khz hum that goes up and down with the volume control. It's quite annoying when the volume is at a reasonable level and increases from there.

Notes:

1. Everything appears to be grounded.

2. The hum goes away when I turn the speech potentiometer all the way down on the Squawk and Talk. Not a satisfactory fix!

3. The hum is not affected by the BG sound pot, I can crank it with speech down and all good.

4. The say it again appears to do nothing when I turn either pot on it.

I'm not a smart man, but I suspect it has to do something with the pictured mess of a wiring harness between the Say it Again and ST board, which has bare wires and a cocoon of electrical tape.

A couple questions:

1. I keep reading about the FF jumper on the ST board, which I presume is off since I get no sound if I remove the say it again connector. I'd like to remove the say it again from the chain to confirm the harness is the issue, but sound cuts off when I disconnect. I'm guessing closing jumper FF would allow me to power the ST without the say it again. So... where is jumper FF on the board, and how the heck do I close the connection to see if that makes the hum go away?

2. Can some kind soul post pictures of the standard harness between the ST and Say It Again so I can attempt to wire a new one after verifying that is the issue? I'm also happy to pay somebody smarter than myself to whip me up one, but that's kind of the coward's way out.

A million thanks in advance!

ST_1 (resized).jpg

ST_2 (resized).jpg

ST_3 (resized).jpg

Yes, there is echo and distortion. Although no perceptible changes when I twiddle the 2 knobs.

Thanks, I have a repro say it again but looked at the original and appears J1 is the 5 pin on the top of mine. Will report back later with my findings.