My TC500 radio has no tx audio

ALTAI PWR MIC - black/braid= earth, red=RX, white=TX, Yellow=MODASTATIC - blue/braid=earth, black=RX, red=TX, white=MOD, Yellow=Spare
SIRTEL ECHO MIC CBE 2002 - black/braid=earth, blue=TX, white=RX, red=MOD007 POWER MIC - brown/braid=earth, green=RX, white=TX, blue=MODSADELTA EC 980 - braid=earth, green=RX, brn=TX, white=MOD
or braid=earth, black=RX, blue=TX, white=MOD

pin 1 ground
pin 2 audio
pin 3 TX
pin 4 not used on other mics or has 8v on TX for powered mics
pin 5 not used on other mics
pin 6 not used on other mics

eft is echo, freq display, talkback..
any mic can go on any radio.. just wire it correctly. and have a mic in the radios Ohm range impedance.
1. ground, 2 audio, 3 TX 4. RX not used.
so any cobra wired mic will work. or a $9 stock replacement mic. or a $39rk 56 mic. or $19 astatic mic wired for cobra/uniden. from any radio shop or truck stop.. the above are Retail prices for the temple, tx area..

Don't worry about colors. look a the mic switch connections. one wire will be a common ground for TX & RX the middle wire would be ground(pin1) the n/c side will be RX pin4 the N/O side will be TX.... the same for the audio element side, one will be ground and the other will be audio pin 2.. this works for any mic and any radio.


pin1 ground pin 2 audio, pin 3 TX, pin4 RX.. standard pin outs cobra / galaxy/connex exports

one should be a ground. look at the board were the wire is.. and its obvious that its a ground pin 1. then should have 3 remaining. one will be tx.. touch the others to ground to see which one makes it tx.. theres your pin 3 tx.. on a galaxy pin 4 is not used. thats rx pin4 cobra radios would have a increase in rx audio when this is connected to grnd. the last would be audio. once you find grnd and tx. reconnect mic and put to pin 2 audio. the last 2 wires that gives it audio..

If the radio is not going into TX, then you have not connected the TX line back up,

If there is no audio when you TX you have left the audio wire off.

The radio usually needs 4 wires.
TX (Puts radio into TX)
Audio (this carries the audio from the mic into the modulator)
Screen (ground cable (earth))
RX (not as common these days)

First, try another mic on the radio to be sure it's the mic and not the radio causing the problem. If it's the mic, check the wiring circuits for a bad switch or broken wire. Simply...the TX circuit is closed and the RX is open when the key is squeezed. The RX circuit is closed and the TX circuit is open when the key is released. Use a simple ohm meter to check for resistance between the pins on the mic (after removal from the radio of course). Open circuit will read 1, closed circuit should be very close to zero. You'll probably find the TX circuit never closes when the key is squeezed. Could be a broken wire or faulty switch in the handset.
Also check...If the mic "keys up"...you see the meter move normally, but no voice...it's either a faulty mic element (the little round thing you talk into) or the audio circuit of the radio has a defective component which a good CB shop can replace.

take a wire or small screw driver across any two pins you are looking for a earth from tx to tx the last pin is mic. on mic side use a multimeter earth is braid, find rx lead next . key mic multimeter shows 0 tx. audio has a higher value .

How are you testing the audio out?
Are you using another radio?
If so, are you REALLY sure the other radio is ok?
If the other radio is ok, how do you know the mic is ok? have you tested it with another radio?
If the mic is ok, id have a look at the mic socket to check that all the pins are still there. Then open the radio up and check the socket is still connected to the main board.

Let me know how you get on..
M3ODQ

Hi,

Most standard CB microphones are 4 wires:
Audio IN (from Mic)
Speaker
PTT (TX)
Ground.



To determine which is which on the radio side:
a. the Audio IN (from Mic) would read a high resistance to ground (chassis) of CB radio;
b. the Speaker when connected to the ground would activate the receive speaker. To verify, power up the radio, squelch all the way down, when shorted to ground, speaker will produce background noise/sound;
c. when PTT (TX) is shorted to the ground, the rig will transmit and the red TX indicator will light up;
d. Ground. when tested with an Ohmmeter to the chassis will read 0 ohms.

Hope this be of some help/idea. Pls post back how things turn up or should you need additional information.

Good luck and kind regards.