There is a very good procedure on you-tube to determine the pin-out for a CB microphone. A combination power meter-modulation meter is used. Where can I obtain one of these?

 

https://www.hamradio.com/catalog.cfm

Regards, Dana.

 

https://www.hamradio.com/catalog.cfm

Regards, Dana.

Thank you Dana...I could not find anything about modulation-power meter in the HRO catalog. Regards, KB3TZB

 

I found Kris RF Power, SWR and Modulation Tester on EBAY. Thanks to all who helped. Regards, KB3TZB

 

That kind of meter is one that I would not choose to discover the pin connections for a 4-pin microphone connector. Unfortunately there are a whole lot of possibilities, many are vastly different. Radios with "electronic" switching, that have no relay for changing over between transmit and receive, are far different from those that use a relay for the changeover. The switch in the microphone is quite different as well.

Is this a case of having a radio and the microphone connector has come off? Or a radio with no microphone? Or hoping to put a different microphone on a radio that has one that you want to replace? That case is the simplest one. Also, do you have a meter that can measure resistance and voltage? That can be very helpful.

 

You can find the microphone pinout for a large number of cb radios here: http://www.cbtricks.com/

 

I found Kris RF Power, SWR and Modulation Tester on EBAY. Thanks to all who helped. Regards, KB3TZB

It would be interesting if you could summarize the method for determining the connections with that kind of meter. Really. If the radio has a change-over relay then finding the correct connection would not be very difficult. If not, and it has electronic switching, then it gets fairly complicated.

 

The microphone plug for my old Courier Redball was broken off and only the shield wire was connected. I found a new plug, and I intended to solder the wires to the pins. Using the video in the first post I intended to determine which lead went where. On a website I found that the leads are numbered counter-clockwise looking into the radio starting to the left of the notch: 1-Yellow or Black; 2-White; 2-Red; 4-Shield. The existing shield matched this arrangement. I have a Fluke 85 V meter.
I connected the radio, a roof mount antenna, 12 Vdc power supply, and the microphone. It seemed to be working, but I made no contacts.

 

Several possibilities exist for not being able to make contacts. The first question is are you able to receive anything? If you can hear voices fairly well then the antenna connection is OK, and that is a good start. I am not sure if that radio has a change-over relay or if it uses electronic switching. Since you seem to have the original microphone, you should be able to open it up and verify that the push-to-talk switch is working, and that the contacts to enable the transmitter are closing. If the switch is working then you can verify continuity of each of the wires in the microphone cord. Sometimes those wires do open up near one end or the other.

Before going much farther, it may also be possible to locate a copy of the radio circuit schematic diagram on line. That will be the most useful tool of all, since not only will it show the connections from each pin inside the radio, but they also usually show the microphone connections themselves. color codes are not always correct, and they all presume that nobody has changed anything. Of course, I have been presuming that you are able to read and understand a schematic diagram.If that is not the case then the task gets more complex.

 

I got the instruction manual with schematic from the internet. I hear words occasionally. We live pretty far out in the boonies for highway traffic. The built in meter shows a fair deflection to the right and full deflection with the microphone switch closed. The controls are very scratchy including channel switch, volume and squelch. I used this radio when I was a fireman in the 1970's. I found it about a month ago and have been tinkering with it.
Thank you for your interest in my project...

 

I am always interested in radio projects, and if your nickname is accurate, you are also a ham radio person. So am I, N8QVS, but I did not change my call when I upgraded. I have repaired a few CB radios, including some that had been really "worked on", attempting to add more channels when 40 channels became available. The interesting one is a classic, and SBE "Formula D", with a PLL synthesizer using TTL logic ICs instead of a programmable single IC arrangement. The project for CB that I think will be great is a squelch circuit that triggers on voice patterns instead of carrier strength. It was published in QST quite a few years back, with a couple of errors in the circuit. So I have been working on creating a circuit board version small enough to add to more current radios.

 

I got the instruction manual with schematic from the internet. I hear words occasionally. We live pretty far out in the boonies for highway traffic. The built in meter shows a fair deflection to the right and full deflection with the microphone switch closed. The controls are very scratchy including channel switch, volume and squelch. I used this radio when I was a fireman in the 1970's. I found it about a month ago and have been tinkering with it.
Thank you for your interest in my project...

There may possibly be a problem in the microphone itself, or in the connection. To check that you could connect an external speaker to the PA jack on the radio. A cheap and easy way to verify microphone functioning.

 

Thank you Mr. Bill...I will try that. I may try to find someone to overhaul it.

 

Thank you Mr. Bill...I will try that. I may try to find someone to overhaul it.

If you get good audio from a speaker connected to the PA jack, that tells you that the microphone and connections are good. This would be where a wattmeter might be useful. Or even just an output meter.