Turner SSB Plus 2 4 Pin Mic to A Uniden Washington MB8719

[cadillaccharlie]

Hi all! I need some mic-wiring advice. I have a Turner SSB Plus 2 4-wire connector desk mic that I want to use on my Uniden Washington MB8719 which uses a 5-wire mic connector. The color code on the Turner mic is Red, Black, White & Shield. Will a 5-pin to a 4-pin mic adaptor work? If I don't use an adaptor, how do I wire this 4-pin Turner mic to a 5-pin plug that I have on hand? Thanks in advance for any help!

Dave

[cbrown]

Jun 25, 2024 13:39:41 GMT -5 cadillaccharlie said:

Hi all! I need some mic-wiring advice. I have a Turner SSB Plus 2 4-wire connector desk mic that I want to use on my Uniden Washington MB8719 which uses a 5-wire mic connector. The color code on the Turner mic is Red, Black, White & Shield. Will a 5-pin to a 4-pin mic adaptor work? If I don't use an adaptor, how do I wire this 4-pin Turner mic to a 5-pin plug that I have on hand? Thanks in advance for any help!

Dave

It's pretty easy. First, turn the microphone over so you can see the underside and have the push-bar and mic element facing your chest. Make sure the switch behind the battery tray is pushed to the rearward position (where the microphone cable enters the mic).

Wiring is then:

Pin 1 - White wire
Pin 2 - Shield
Pin 3 - Red wire
Pin 4 - N/C
Pin 5 - Black wire

You normally don't need a jumper connecting Pin 2 and Pin 4 as that is done in the radio, HOWEVER I've heard some radios may require the jumper on the mic connector. Try it first without the jumper and see how it goes. If it doesn't switch between RX and TX (and you've verified the switch position under the mic is correct), you can try adding a jumper.

[cadillaccharlie]

Thanks a million for the info! Much appreciated!

Dave

[2600]

This does pose an arithmetic problem. This came up a lot when the Uniden SSB radios with the 8719 and 5-pin mike first hit the market 45 years ago. Six-wire mikes were suddenly hard to find. Most base-station power mikes had four wires in the cord. And the customer just wanted to use his favorite (4-wire) mike on his new radio.

The arithmetic problem is that four doesn't equal five. The four-wire cord has only one ground connection, the shield wrapped around the audio wire. A stock mike for the Cobra 2000/142/Madison/etc has five wires in the cord. This provides two ground circuits. One for the audio alone on pin 2, one for the transmit/receive switching alone on pin 4.

You have three choices. Hook the ground to pin 2 only, hook it to pin 4 only, or tie a jumper wire from pin 2 to pin 4, and hook the shield to that.

One will tend to have feedback squeal on receive, especially sideband receive. The other will tend to squeal on AM transmit. The third choice offers the possibility of feedback issues for both.

We developed and adapter board that lived on the rear of a 4-pin mike socket. It has a relay on it that keeps the keying ground separate from the audio ground. It came about so a roger-beep/five-tone beep/roger-K board that lacked a relay could be used in a 5-pin radio. A roger beep has to keep the speaker switched off until the radio drops out of transmit. Without that relay, the speaker would come alive when you released the PTT button and the beep would break your eardrums. Or your speaker. Or maybe both.

Still haven't put together the instructions to make it a proper product for sale.

73