Help with Radioshack 21-1177 power mic

[Turbo T]

I have a 21-1177 power mic. When plugged into my TRC-30A it sends an AM carrier but no modulation. I know it's not the radio because a stock mic works fine on it. I've checked the batteries, both of them have a 1.6V charge. I checked the volume on the mic, it's all the way up. (even tried it all the way down)

The wiring on the mic is as follows:

1 shield
2 red
3 white
4 yellow
5 black

Anyone have any ideas? Maybe this is just the wrong mic for my radio?

Thanks in advance

 

[midnight special]

try the mike in another radio shack radio,,, if it is the newer power mike the electrc element might be bad. check and make sure the cord is not shorted or have a broke wire in it. 73s midnight special

 

[jimbr1]

I would do as midnight special suggested if you have another radio shack radio available. If not, check the continuity of each of the 5 wires between the end of the plug and inside the microphone. Also check all connections inside the mic (looks to be an old radio and old mic- nothing wrong with that but parts wear and connections can go bad). Interesting enough (according to an illustration by google) there is an actual switch that turns the preamp off and on...if this is the case, check that switch (or jump it to make sure it is on. If you are throwing a carrier when you press the mic switch, it sounds like an audio problem (maybe the preamp isn't working)...good luck!

 

[Onelasttime]

I know it is an old post. If it is the modern 21-1175 that is kind of cone or pie slice shaped with a taper and with a7v batter with a batt test button I can tell you more.

First it has a dynamic mic element and if the battery goes dead it functions as a regular mic. It was built for RadioShack by Sony and they did not make that model that long. I had one that lasted me from 1991 to 1998 when it was stolen with my RCI2950. It was a fantastic mic and I chose it over the old D104M6B. I tried every power mic I could get a hold of from freinds and from the electronic shop I was aprenticing at.

I would check the wires, the socket, and the PTT switch.

The circuit is so simple that you should be able to trouble shoot it with a VOM.

 

[Rick330man]

I have one of those. It says Radio Shack on the bottom of the front. The amplified part died years ago. I just use it as a replacement stock mic. My experience is that Radio Shack CB products of this later era were not on par with their 1970s and early 80s gear.

As an example, I also have the older, Made in Taiwan version of the mobile, noise cancelling mic. It says Realistic and runs on a 7 volt battery. It must be close to 30 years old. It is still an exceptional performer and is one of the best sounding mics I have ever heard on those old Uniden chassis Realistic radios of the 70s and 80s.