k40 microphone

[d-minus]

O.K. i just picked up a old k40-7 speech processor cb radio. The mic will key up radio but no modulation. I have some cobra mics, but none work with that radio. How do you wire one of those mics to work with this radio or if it is to much hassel how can i tell what is wrong with original mic. Thanks for any help, i would like to try this radio out. D-minus

[295 antenna]

I found this: http://www.cbtricks.com/mic_m ... g_book.pdf

[d-minus]

Thanks for the lead i looked at it. The problem is the mic does not have a high/lo switch on top nor does it have a adj pot in mic at bottom where cord comes in for mic gain. I does have a magnet in the mic to hold it to something metal. Besides that it is just a stock looking mic. It may be a replacement mic somebody put on it. I have seen some pictures of a mic that has alot of what looks like caps,diodes,adj pot etc. But this one is not. D-minus

[milkman21218]

The old K-40 CB's were wire the same as the old 4 pin General Electric CB (5813, 5816, Etc.) radios.

[d-minus]

Thanks for that, i'll see if i can figure it out. D-minus

[milkman21218]

The Cobra/Uniden 4 pin Mic

Stock
1- Shield
2- Audio
3- Transmit
4- Receive

The GE/K-40 4 pin Mic
Stock
1- Audio
2- Shield
3- Receive
4- Transmit

[pabxone]

I wonder if you have a problem with the radio and not the microphone , since it appears that you have a few microphones all doing the same thing ?

Having said that , The Non Amplified K40 microphones do have a history of the mike elements going faulty.

The K40's are good mikes and worth the effort of repairing, even the non amplified ones

[d-minus]

Thanks, milkman for your effort i'll wire one up and see what happens. Pabxone i was woundering the same thing, now for the mic it's pretty beat up looks like it's been a dog chew toy holes every where something has been poured on it or leaked on it in the mic element. The radio is in good shape just looking at the outside and inside. I guess i will find out. I appreciate all the help guys thanks allot. Daniel

[973Kid]

I'm more of a paint by numbers kinda guy. I bought the same radio at Goodwill for $2 but it didn't come with a mic. Not a big deal since I have plenty of extra stock Cobras laying around. Since I'm not a tech and I am only at the point of starting to learn to work on my pile of non working radios I don't know whoch wire does what. How do I figure out which wire is transmit, receive and audio? I can say it is funny when you put a Cobra mic on a K40-7 and key the mic. The mic turns into an external speaker.

[ Post made via Samsung Galaxy S5 ]

[dmilner]

i would start with look online for the pin out for the mike. write it down and then look up the pin out for the radio and do the same. thats how i started.. figure out which wire goes where from the on line diagrams. something like google search k40 mike pinout .

[MDYoungblood]

I'm more of a paint by numbers kinda guy. I bought the same radio at Goodwill for $2 but it didn't come with a mic. Not a big deal since I have plenty of extra stock Cobras laying around. Since I'm not a tech and I am only at the point of starting to learn to work on my pile of non working radios I don't know whoch wire does what. How do I figure out which wire is transmit, receive and audio? I can say it is funny when you put a Cobra mic on a K40-7 and key the mic. The mic turns into an external speaker.

[ Post made via Samsung Galaxy S5 ]

If you look at milkman's post it gives which pin does what, you could use a multi-meter to check the pins as long as the mics still have the old 4 pin plugs on them. Giving the pinout is the easy part, telling you the color of the wires is not always as easy since the manufacturer's never had a set standard on color codes and that is true even up to today's mics and radios.

3's

Greg

[dmilner]

i always write down what color of wire is on what pin when i open up the radio or the mike wire. that solves the issue of what color does what.

[MDYoungblood]

i always write down what color of wire is on what pin when i open up the radio or the mike wire. that solves the issue of what color does what.

Now a days I have been rewiring the radio itself to accept the Cobra/Uniden/Galaxy pinout, makes life a lot easier to walk into a truck stop and buy an off the shelf mic if your's would break while on the road.

3's

Greg

[973Kid]

i always write down what color of wire is on what pin when i open up the radio or the mike wire. that solves the issue of what color does what.

Now a days I have been rewiring the radio itself to accept the Cobra/Uniden/Galaxy pinout, makes life a lot easier to walk into a truck stop and buy an off the shelf mic if your's would break while on the road.

3's

Greg

Both great ideas. Hopefully I can get more comfortable working on tadios so I can try rewiring the radio to match the mic. I am only working on radios that don't work to start with so I don't damage anything worth anything. The next radio I will be looking at powers up but has no tx showing up on the meter. That one should be more fun. I am actually hopi g it's a mic issue but thats not my kind of luck. I am keeping the Tramm Diamond 60
for last because I really want that one to work at some point.

[ Post made via Samsung Galaxy S5 ]

[MDYoungblood]

Your in luck, that Tram is wired the same as Cobra.

3's

Greg