TK 790 mobile wiring

[midstate33]

I am trying to get a Kenwood KMC 30 mic to wire
to the DB 25 connector on rear of TK790, have
PTT but no voice anyone who has been successful
with this I would greatly appreciate any help
Tnx W8WAR

 

[mmckenna]

I don't have my software here, but you should need to set up the Mic Input to use the port. On the newer radios theres a page for this on the KPG that lets you assign the rear mic input for data or voice.

 

[n7maq-1]

You need to move R641 to R640 for mic audio.





MI/DI (MIC Signal Input/Output or Data Audio Input)
This pin has one of the two functions listed in Table 3 by
setting jumper resistors (0 ohm) R640 and R641 on the
control unit (X57-561 B/3) (Refer to page 21).
1) MIC signal input/output
This pin is directly connected to the MIC input pin of the
transceiver, so it has the same function as the MIC input
pin. When the input is 5mV/3 kHz, DEV (600 ohms)
modulation is obtained. The MIC input is output from the
transceiver panel as it is.
2) Data audio input
The signal from this pin passes through the LPF (fc: about
10kHz), is summed with the MIC AMP output, and goes
to the modulator. Therefore, it is not preemphasized.

 

[mmckenna]

You need to move R641 to R640 for mic audio.

Thanks, I was thinking 5710….

 

[midstate33]

Ok guys really appreciate the answers/help but I have tried the things you suggested, I should have added that by applying signal from function generator and keying mic I have good transmitted audio, I also applied dc voltage to appropriate pin on KMC 30 powering the electret in mic (?) I believe there is a switching problem in the mic circuit preventing audio getting to db25 mic input pin, the KMC 30 works just fine on tk7180, really got me stumped, any help is appreciated, tnx 73’s
W8WAR

 

[ramal121]

So you did switch/confirm the internal jumpers? If the radio is set for data you can still pump audio in but at a much higher level than the mic element will ever produce. Input absolutely needs to be set for "MI".

The grounds for PTT and the mic element are separate and you need to connect both. Pin 3 "E" and pin 5 "MIC-E" need to go to the respective pins on the 790 25 pin connector.

 

[midstate33]

I don't have my software here, but you should need to set up the Mic Input to use the port. On the newer radios theres a page for this on the KPG that lets you assign the rear mic input for data or voice.

Done

 

[midstate33]

You need to move R641 to R640 for mic audio.

View attachment 124707

View attachment 124708

MI/DI (MIC Signal Input/Output or Data Audio Input)
This pin has one of the two functions listed in Table 3 by
setting jumper resistors (0 ohm) R640 and R641 on the
control unit (X57-561 B/3) (Refer to page 21).
1) MIC signal input/output
This pin is directly connected to the MIC input pin of the
transceiver, so it has the same function as the MIC input
pin. When the input is 5mV/3 kHz, DEV (600 ohms)
modulation is obtained. The MIC input is output from the
transceiver panel as it is.
2) Data audio input
The signal from this pin passes through the LPF (fc: about
10kHz), is summed with the MIC AMP output, and goes
to the modulator. Therefore, it is not preemphasized.

Done

 

[midstate33]

Can a KMC 30 be wired to tk790 db 25 connector
(forget the theory has anyone done it?)

 

[ramal121]

A certain sheriffs office wanted a second mic on the passenger door so they can stand up out of traffic and use the radio. 790's with KMC35. Installed lots. Any Kenwood mic should work.

 

[midstate33]

A certain sheriffs office wanted a second mic on the passenger door so they can stand up out of traffic and use the radio. 790's with KMC35. Installed lots. Any Kenwood mic should work.

Was this mic connected to the db 25 ?

 

[ramal121]

Yes

 

[mxer683]

@ramal121 I've scoured the internet and your post here seems to be the closest to what im looking to do. My intended setup is similar to the example you gave of the sheriffs office setup, two mics, one plugged into the basic function remote head, and the other to the db25 connector. In that instance is the jumper still moved from 641 to 640? Or do both 641 and 640 need to be jumped in order for both mics to be operable?

 

[n7maq-1]

@ramal121 I've scoured the internet and your post here seems to be the closest to what im looking to do. My intended setup is similar to the example you gave of the sheriffs office setup, two mics, one plugged into the basic function remote head, and the other to the db25 connector. In that instance is the jumper still moved from 641 to 640? Or do both 641 and 640 need to be jumped in order for both mics to be operable?

Yes you still need to move the jumper, R640 in and R641 out.

You will also want to do a hot mic mod, as both mics will be "hot" when one or the other is keyed.

 

[mxer683]

Yes you still need to move the jumper, R640 in and R641 out.

You will also want to do a hot mic mod, as both mics will be "hot" when one or the other is keyed.

You're awesome! Thank you!

 

[n7maq-1]

You're awesome! Thank you!

I have attached the hot mic mod for the KMC-27 and the KMC-65. For the KMC-35 just open it up and cut the green wire.

 

[mxer683]

@n7maq-1 and the hot mic is only necessary should both mics be plugged in simultaneously? I haven't fully decided but though I certainly need both mic jacks to be operable I may just leave one of them unplugged at any given time.

 

[n7maq-1]

Correct, you only need to do the mod if both mics are hooked up at the same time.

 

[mxer683]

@n7maq-1 One last question somewhat off topic as I think this only applies to a kmc27 mic. But in order to have full functionality would I wire up db25 pins 14 and 17? Looks like the mic accepts 8v and pin 14 is 13v?

 

[ramal121]

Well that depends on which KMC-27 you are referring to. The KMC-27 is for the TK-X90 and has the round plug and the KMC-27A has a RJ-45 8 pin plug. Both requires a 12 volt input to operate. Actually the SB+ line goes to a 5 volt regulator for the internal ops so either 12 or 8 volts should work. Both these are noise canceling mics.

Now a KMC-27B has a RJ-45 plug used in all the other popular mobile radios and does not require any voltage input to operate. This mic is not noise canceling. Which are you referring to?