I have been asked to do a repair on the microphone of a FT5200 for a friend. The fault is that while the radio transmits and receives quite well, it does not switch back to receive when the PTT button is released. To switch back the radio must be switched off or the power momentarily disconnected.
Since the radio would be used in a mobile application, that is totally unusable.
Opening the microphone, which includes a full tone keypad and several other functions, reveals a whole lot of very tightly packed circuitry on one double-sided multi-layer circuit board.
After a bit of research I found that this is the most common failure mode with this product. REplacing the microphone will run well over $100 USD and that does not seem like a fair choice.

QUESTION: Has anyone located the specific failed component and effected a repair?? OR has anyone even located the circuit for this microphone?? The circuit does not seem to be readily available, at least I have not located a copy.

 

Hello,

Here is the service manual of the ft5200:
https://www.jabse.com/L1lBRVNVL0ZUNTIwMC5wZGY-
https://www.jabse.com/L1lBRVNVL0ZUNTIwMF9zY2gucGRm

Bertus

 

To switch back the radio must be switched off or the power momentarily disconnected.

Unplugging the mic doesn't unkey the rig?

 

Unplugging the mic would also release the lockup condition. But unplugging the mic is not a trivial action because the radio uses a seven pin screw-on connector. So the problem is in the microphone electronics, which are quite complex.
AND reaching for the radio while driving would certainly be very unsafe.
THAT is why I am seeking a circuit schematic of the microphone, so that hopefully I can determine which component or components to replace.

Thanks for responding, though.

 

THAT is why I am seeking a circuit schematic of the microphone,

I have looked at several service manuals on this radio and not a single one shows the mic schematic, only the 8 pin receptacle.
Further reading suggest doing a reset.
Read where other users experienced the same problem, seems like it might be RF related where the transmit signal is getting back into the radio and causing the problem.
Reset

 

What I have not yet done is try a different microphone of the same model. That should verify if it is the mic or the radio.
I suppose that RF in the mic could be the problem, but since it happens both with the original user at their location and at my house with a good dummy load connection, RF on the mic input does not seem probable.
A "factory reset" is a possibility but that will mean re-entering a whole lot into the saved memory.
AND the fact that it seems that other have had the same problem points more at the microphone.

I do have another microphone that I could change the connector and the cord and the plug, and use. BUT that mic is a dynamic mic, not one with a whole bunch of electronics in the case. So I do not know if the audio output from the mic would be adequate for that radio. The specifications in the manual do not specify the required mic signal level.

 

With the dummy load does it lockup consistently on high and low power on both bands?

 

Unplugging the mic would also release the lockup condition.

Identify which wire on the mic cord when disconnected releases the tx.
Connect that wire through a small NC push button switch and install it in a convenient place on the mic case.
Might start with pin7 as it's the ground or pin4.