Kenwood TK-890H, 790H Auxillary

[KW6MOT]

Hi all, I have a complete dual band setup,with a Kenwood TK790H/890H with the advanced head and KRK7DB. I have an offroad lightbar on a relay and my emergency response lights on another relay running to independent switches. I have read the service manual and regualr manual about the AUX ports. I have metered each port and it pushes out about .3V if I ground it to the battery and 1.5-1.7v if I ground it to earth on the radio.

Now that you know what I have, I am trying to have each relay trigger, 1 for the emergency lights and 1 for the offroad light bar, be anabled from AUX A and AUX B. I have 2 buttons programmed as AUX A and another as AUX B. I can't get the relay trigger wires to enable the relay because, I believe the voltage is to low, I would like to know what I need to do to be able to run the relays or if you have any other suggestions.

Thank you, KW6MOT

 

[mmckenna]

From the service manual:

18. AUX A, AUX B, AUX C
This function switches the accessory PF Output ports which have been programmed with AUX A, AUX B and AUX C.
Press [AUXA] Key. A confirmation tone sounds, the A icon is displayed, and the AUX A Port is switched on (Low level). If [AUXA] is pressed again, a confirmation tone sounds, the A icon goes off and the AUX A Port is switched off (open collector). In the same way, [AUXB] Key controls the AUX B Port, and [AUXC] Key controls the AUX C Port.

The port on the DB-25 is the collector side of the transistor. Here's a page on how to wire that up to control a relay:

How to Connect a Transistor as a Switch in a Circuit

In this article, we will show how to connect a transistor in a circuit so that it acts as a switch to turn on or off a load.

www.learningaboutelectronics.com

I -think- it'll handle 100ma maximum.

 

[KW6MOT]

From the service manual:

18. AUX A, AUX B, AUX C
This function switches the accessory PF Output ports which have been programmed with AUX A, AUX B and AUX C.
Press [AUXA] Key. A confirmation tone sounds, the A icon is displayed, and the AUX A Port is switched on (Low level). If [AUXA] is pressed again, a confirmation tone sounds, the A icon goes off and the AUX A Port is switched off (open collector). In the same way, [AUXB] Key controls the AUX B Port, and [AUXC] Key controls the AUX C Port.

The port on the DB-25 is the collector side of the transistor. Here's a page on how to wire that up to control a relay:

How to Connect a Transistor as a Switch in a Circuit

In this article, we will show how to connect a transistor in a circuit so that it acts as a switch to turn on or off a load.

www.learningaboutelectronics.com

I -think- it'll handle 100ma maximum.

Thank you. I will take a look at that.

 

[byndhlptom]

The link mmckenna referenced is using a NPN transistor to supply a ground to a relay, activating it. The AUX port does not source voltage, so some level conversion may be needed

If the relay you are using is low power (ie, less that 100mA coil current. you should be able to use the AUX output to drive the ground side of relay directly. I would verify the AUX port current limit before doing this.

If not, then you need to look at using a PNP transistor to drive the high side of the relay. The ground from the AUX port would drive the base of the PNP, sourcing current to the relay.

If you are not sure of the transistor logic, then do some studying or have some one local assist you. There are bias and series resistors that need to be part of this hookup.....

There are relay interface kits out there, that is another option.....

$.02

 

[KW6MOT]

Thank you. I will look into it. I have use the transistor method once but not radio wise. I will take a look at the relay interface kits. If I am understanding you correctly, the AUX ports supply the ground to the relay?

 

[mmckenna]

Thank you. I will look into it. I have use the transistor method once but not radio wise. I will take a look at the relay interface kits. If I am understanding you correctly, the AUX ports supply the ground to the relay?

Correct.

 

[KW6MOT]

Thank you both for the help. I rewired my test relay/light setup to have a negative trigger and it worked.

 

[KW6MOT]

Correct.

One more question, on speaker output in this dual band setup can I run speaker output out of Radio 1 or does it need to run from the head?

 

[mmckenna]

You can use the 12 pin accessory connector on the back of the control head with one speaker. That will put both audio signals from both RF decks onto the same speaker.

Or, you can install separate speakers on the RF decks. But each RF deck will only give you it's own audio out the speaker connection.

 

[KW6MOT]

Oh ok. Thank you.

 

[KW6MOT]

You can use the 12 pin accessory connector on the back of the control head with one speaker. That will put both audio signals from both RF decks onto the same speaker.

Or, you can install separate speakers on the RF decks. But each RF deck will only give you it's own audio out the speaker connection.

Sorry I more question. In the service manual it says do not ground the speaker output pin because the BTL. Not sure what that is, but what pins would I connect the speaker to then?

These questions may be stupid, but I mainly use Motorola, But am digging into kenwood again. I used to use 7180/8180, 7160/8160, 630H and a bunch of other handhelds.

 

[mmckenna]

On the back of the radio is a 9 pin Molex style connector.
On that:
Pin 2 and 6.

If you are using the remote head kit, it has a 12 pin Molex style connector.
On that:
Pin 10 and 11

Both speaker terminals on each connection are isolated from ground. If you ground one of the pins, it'll damage the audio amp IC. Just run 2 conductor cord from the radio to your speaker. Old auto stereos would sometimes ground one side of the speaker feed to save wire. They just don't want you doing that. This is pretty common, Motorola radios are the same way.

 

[KW6MOT]

On the back of the radio is a 9 pin Molex style connector.
On that:
Pin 2 and 6.

If you are using the remote head kit, it has a 12 pin Molex style connector.
On that:
Pin 10 and 11

Both speaker terminals on each connection are isolated from ground. If you ground one of the pins, it'll damage the audio amp IC. Just run 2 conductor cord from the radio to your speaker. Old auto stereos would sometimes ground one side of the speaker feed to save wire. They just don't want you doing that. This is pretty common, Motorola radios are the same way.

Got it. Thank you. I always like learning more in depth.

The XTL's already habe the 2 pin Molex on so its usually just plug and play into that or if you add a different speaker you would tap into that on XTL and APX mobiles.

 

[KW6MOT]

On the back of the radio is a 9 pin Molex style connector.
On that:
Pin 2 and 6.

If you are using the remote head kit, it has a 12 pin Molex style connector.
On that:
Pin 10 and 11

Both speaker terminals on each connection are isolated from ground. If you ground one of the pins, it'll damage the audio amp IC. Just run 2 conductor cord from the radio to your speaker. Old auto stereos would sometimes ground one side of the speaker feed to save wire. They just don't want you doing that. This is pretty common, Motorola radios are the same way.

Now I have an issue and I believe I know what it is, but I wanted to get your input.

I have everything installed with the speaker running from the 12 pin Molex on the head. I had 0 audio out. I had the jumpers on the rear of each radio,from pin 6 to 2. I then tried a speaker with a 9 pin on it on the back of each radio the 890H, the main radio pushed audio out to its own speaker. The 790H produced no audio when I hooked the same speaker to the rear of the radio on the 9 pin.

However, when moving the jumpers to install the KRK7DB kit I noticed this which jumps from F501 (which after some digging in the service manual is a .5amp fuse) to SB which I have no idea what it is. I was thinking switched battery but not sure.

 

[mmckenna]

Yeah, SB is switched power. Looks like someone jumpered around a fuse?

That modification sends SB to pin 14 on the 25 pin connector. Someone was probably using it to feed power to an accessory.

As for the no audio, the RF deck requires some modification depending on how you want to route audio to the control head. Grab the manual for KRK-7DB and take a look at that. You'll need to compare it to how your radio is currently and adjust accordingly.

 

[KW6MOT]

Yeah, SB is switched power. Looks like someone jumpered around a fuse?

That modification sends SB to pin 14 on the 25 pin connector. Someone was probably using it to feed power to an accessory.

As for the no audio, the RF deck requires some modification depending on how you want to route audio to the control head. Grab the manual for KRK-7DB and take a look at that. You'll need to compare it to how your radio is currently and adjust accordingly.

Oh I didn't know there was a manual for the kit. Thank you.