Kenwood tk 790

[firemedic502]

Hello, I am in the process of installing a david clark headset system to a Kenwood tk 790. The interface wires coming from the headsets is red - mic high, white - mic low, green - audio high, black audio low, blue - ptt low, yellow - ptt high. Just below the black wire the have ground on the radio side with the install diagram. I will be using the 25 db accessory connector. Can anyone let me know what pins to use from the kenwood to connect to the headset interface.

Thank you,
Joe

 

[ramal121]

Red > Pin 13
White > Pin 25
Yellow > Pin 2 (Then program AI1 as EXT PTT in FPU)
Blue > Pin 7
Green > Speaker
Black > Speaker

You'll have to open radio and look at jumpers R640/R641. Need a jumper on R640 and R641 left open to get mic from DB-25. Default is other way around from factory.

Also mic drive from David Clark will probably be way too high for a 790 and will have to be turned down quite a bit.

 

[firemedic502]

Thanks for the info, this helped out a bunch. I did not have to change jumper setting. It is working properly now.

 

[firemedic502]

Kenwood tk790

In reference to the david clark headset to kenwood tk 790. I am able to transmit with mic from david clark headset but the volume is low when using it and seems weak on transmit. I have no issues with the radio mic but I am not getting the transmit power with the headset mic. Do you know what might be causing this? Is this due to the R640/R641 issue?

Thanks,
Joe

 

[ramal121]

In reference to the david clark headset to kenwood tk 790. I am able to transmit with mic from david clark headset but the volume is low when using it and seems weak on transmit. I have no issues with the radio mic but I am not getting the transmit power with the headset mic. Do you know what might be causing this? Is this due to the R640/R641 issue?

Thanks,
Joe

Yes it is. If 641 is in and 640 is out, the mic input on the back of the radio chassis is set for data transmit in (like for a GPS) and requires LOTS of drive, more than the DC can provide.

BTW, these jumpers are for the radio connector only. If headsets are connected to the control head, this is mic only and no jumpers to worry about.

If you need a map to those jumpers, let me know.

 

[firemedic502]

Thanks again for the info. I did find the R640/R641. The R641 has a small resistor looking device and the R640 is open. I do have to remove the R641 correct and close the R640 circuit correct?

Thanks Joe

 

[ramal121]

I do have to remove the R641 correct and close the R640 circuit correct?

Correct. The jumpers are 0 ohm SMT resistors, very small and take a little bit of nerve. You can remove 641 carefully with a sharp pointed soldering iron. Lift one side and then the other. Or you can destroy it with a small pair of cutters. It's ceramic and will shatter. Just be careful not to wreck the traces or lands on the board.

To install a jumper, get a small piece of wire (I use a strand of cat-5). Bend 1/8" from the end over 90 degrees and tin it with solder. Place the wire across the lands for 640 and tack it down with a soldering iron, then cut off the long piece you used to hold it with.

 

[firemedic502]

Hello again, I was able to remove the r461 smd and did solder a cat 5 wire on the r460. I am able to transmit to our dispatcher now but it still seems that the volume on the trasmit side is low. Do you know if there is any mic adjustment on the david clark system?

 

[firemedic502]

Hello, I figured it out. I had the exteral PTT / with mic mute on in the programming. Working great now.