Kenwood RC2000 (TS-B2000) microphone connections

[K9SO]

I have a new installation trying to use a RC2000 head to control a Kenwood TS-B2000. The radio, control head, and microphone works perfectly when together (no RCC's).

I have them connected via a pair of RRC-1258MKII's and everything works as it should except for the microphone connection. I've had CW on the air QSOs and it all works... until I plug in a microphone into the aux/mic jack of the Control RRC. I have double and triple checked the strapping, but when I plug in the microphone connector, the link keys up the radio immediately (goes to transmit mode). The mic PTT switch has no effect. When the connection to the radio mic input is removed (at the radio end), the Control RCC still appears to key the PTT line (RX audio is muted at the Control end).

The control end cable is a store-bought MJ-88 adapter used per the RRC instructions. Brand new Control RRC, older unit at Radio end.

I'm at a loss as to explain this behavior. I have 4 other sets of RRC's all running perfectly on other radios in my network and I thought I knew what I was doing  ... until now.

Fred
K9SO

[sm2o]

It's obvious that the PTT input pin in the control-RRC is grounded, either the microphone , the adpater cable or the red straps at the control side is wired wrong, it can't be that difficult to find out which

first put in the adaptercable with out mic  and see what is keying already without the mic.

73 de mike

[K9SO]

Yes, it seems simple ... but I already have about 8 hours into troubleshooting this so please bear with me.

The adapter plugged into the aux/mic jack without the microphone does not key the unit. It is a brand new Kenwood MJ-88 and it ohms out as it should.

When I install the red PTT and GND straps only, the unit does not key but the microphone PTT button does not key the unit either.

When I install the MIC GND strap, the unit keys immediately and unkeys when I remove the microphone from the adapter.

I notice that the pin labeled GND on the strapping block is not connected to chassis ground.

[K9SO]

Is the pin labeled "GND" on the aux/mic strapping block supposed to be connected to chassis ground? Because it is not.

[sm2o]

No GND pin is not connected to chassi

i would have removed all red straps and check with an ohm meter which two pins are shorted in the front row of the strapping socket when I push PTT.

those two pins should be connected to GND and PTT on the other side

73 de mike

[K9SO]

Mike,

I could not find any two pins that shorted together following the PTT switch, yet it keyed the radio directly. Of course: the radio supplies power via the microphone connector.

This microphone apparently needs 8-9v of power in order to operate. Adding in the 8v power strap solved the problem. Of course, that is not noted in the strapping instructions for the Kenwoods.

Maybe you could note that this is necessary for some Kenwood microphones in a future manual update.

Thanks for the help.

73,
Fred
K9SO

[sm2o]

OK great that you solved.

What Mic are you using, The Kenwood mics I have seen are simple dynamic mics with a mechanical PTT switch ?

73 d emike

[K9SO]

I have not been able to find a single p/n marking on the microphone, even after opening it up (it is only marked KENWOOD), but it does have a lighted Touch Tone pad. It looks like MC-53DM as seen at this link, but it has the round 8-pin microphone connector that mates with the B2000: 

 https://www.ebay.com/c/2122088269

I was told that it was the original microphone shipped with the B2000, but maybe an original owner can verify that.

I used the power pin strapping as shown in the RRC manual for the D710 setup.

73,
Fred
K9SO