No dummy plug — no problem!

The transport won't move because the remote socket needs a shorting plug that never came with the deck. Fine. Let's build one.

Reading the pinout

Everything you need is at the top of the tape transport schematic (TD-5050). In the upper right corner you can see square boxes labeled 1 to 12 — these correspond to the REMOTE jack at the rear of the unit. To map them onto the plug: the upper left is pin 1, to the right is pin 2, right again is pin 3, and the start of row 2 is pin 4 — three across, four rows down.

The experimental version

This photo was my experimental attempt. I had a case of automotive ends, and one was a blade that would fit inside the socket once I built up its width with a little solder. So I made a Frankenstein jumper that connects pins 1 to 3 to 8 to 11, and a second jumper that connects 4 and 6.

The proper part

The original connector is what's called a Cinch Jones plug — I was able to find one on eBay. There's also a modern replacement available new from Mouser: 538-13121. I'm still waiting for mine to arrive to confirm it fits — I'll update here when it lands.

If your "broken" MX-5050 won't move

Mine arrived with no plug at all — that was the entire fault. The transport control runs through the remote socket, and with nothing closing the circuit the machine looks dead: no motion, no obvious fault, nothing on the meters. If you've just bought an original MX-5050 that "doesn't work", check this socket first — before you open anything.