Tk-790/TK-890 Dual Band Single Head Set up

[jsykora]

I am attempting to set up a TK-790 and TK-890 for dual Band single head set up. The Tk-890 is set up for radio 2 and the 790 is set up for Radio 1. Initally the Head unit got no power. I was able to jump the poser for the head from the 12 pin connector on the back and everything powered up. The Speakers will not work from the back of the head unit, only from pins 2 and 6 on the back of radio 1. when switched to the 890 it beeps constantly when I switch back to the 790 it is fine. When I go to program them it tells me that the models are wrong and would i like to over right them. Then the incesent beeping starts again. What am I missing. This is the first time that I have ever set this up and am having issues with it. I may need to change the firm ware on both radios but what is the latest version and where do I get it. Someone please help I am kind of a rookie with this stuff.

 

[AK9R]

Both radios have to have the same revision level of the firmware. Your Kenwood dealer can upgrade the firmware and shouldn't charge you more than an hour of bench labor.

There are a handful of chip resistors in the second radio that have to be moved or deleted to make dual-band work. It's explained on pages 20-21 in the service manual.

 

[jsykora]

Chips have been moved already. I am guessing it is a firmware issue with the beeping. I am going to try to get ahold of the latest firmware or just have the local dealer handle it. If anyone has anyother suggestions please let me know.

 

[mrweather]

Firmware issues sounds like the cause. It's funny the firmware requiement isn't mentioned in any service manual.

The "incesant" beeping is usually due to frequencies programmed in that are out of the range of the VCO. But with a dual-band single-head setup anything is possible.

Hopefully you'll have better luck with your Kenwood dealer than I had with mine trying to get a firmware update.

 

[ramal121]

When I go to program them it tells me that the models are wrong and would i like to over right them.

Have you changed the radio model info to "dual band" in the software?

 

[AK9R]

The "incesant" beeping is usually due to frequencies programmed in that are out of the range of the VCO.

Quite true. I have a TK-890 that won't lock the VCO on anything less than about 445 MHz.

 

[ramal121]

How old are the radios? This dates back to 2000;


LSB-0248 1/2

SERVICE BULLETIN Land Mobile Division

SUBJECT: KRK-7DB & KRK-8DBH improvements DATE: 3/6/01

As of July 2000, the KRK-7DB and KRK-8DBH remote kits have been changed where the buffer for the
reset circuit has been removed. This change improves the reliability of a dual band configuration where the
radios have been equipped with the LSB-0237 change, and, reduces the possibility of stray RF affecting the
reset circuit. If either of these problems are present, they may appear as a radio which will intermittantly not
turn on or intermittantly have one band with PLL unlock. If the radio installation is using custom length
control cables which are longer than the basic factory cables (KCT-22A/B/C), this circuit change is strongly
recommended - if it has not already been performed by the factory.

KRK-7DB
Radio 1 (X46-3240-22)
1. Delete C9, D1, R1, Q1.
2. Change the resistor R4 from 10k ohm to 4.7k ohm RK73GB1J472J.
3. Add the resistor R92-1252-05 in location of R15.
Radio 2 (X46-3240-23)
4. Change the resistor R15 from 47k ohm to 0 ohm R92-1252-05. (**)
5. Add 0.022uF capacitor CK73GB1E223K between NC line and GND.
KRK-8DBH
Radio 1 (X46-3240-22)
1. Delete C9, D1, R1, Q1.
2. Change the resistor R4 from 10k ohm to 4.7k ohm RK73GB1J472J.
3. Add the resistor R92-1252-05 in location of R15.
Radio 2 (X46-3240-23)
4. Change the resistor R15 from 47k ohm to 0 ohm R92-1252-05. (**)

**A small number of remote kits were released with R15 as 47k Ohm prior to these changes being imple-
mented in production. Most units will be found with R15 already being a "0" Ohm jumper.

Component locations are on the back of this sheet...

 

[ramal121]

The Speakers will not work from the back of the head unit, only from pins 2 and 6 on the back of radio 1.

To utilize the speaker from the head, there needs to be a jumper wire from pin 3 to pin 6 on the connector of radio 1.