Batboard

I have a GTX mobile that powers up and programs just fine. Display is nice & bright, volume knob works as well as power on/off. However, none of the other control head buttons work. Pressing Channel up/down, system up/down, scan, menu, etc all result with no response from the radio.

I swapped control heads and flex jumper with another radio and that didn't fix the problem. The buttons just don't work.

Anyone seen this issue before?

Many times, this model appears to suffer from pressure issues when it comess to activation of the buttons.

In other words, they need a firm and solid finger pressure to make them work, I have had the same problem on one I have also, and it's a pain when I take it in the field as a remote radio.

Pry the front control head off and check the clearance of the buttons to the board, you may have too much clearance for the buttons to actually make physical contact with the board.

This can be a problem after the face has been removed prior, and then reassembled improperly, causing the trouble you reported.

Thanks for your reply. I agree with your comments about the GTX (& LCS) series losing sensitivity on their buttons; however that's not my issue.

As I mentioned, I swapped control heads with a good-working GTX and the results were the same. All buttons work using either control head on a "good" radio but no buttons work using either control head on the "bad" radio. Thus my problem must be related to the actual radio not the control head.

Can't say I've seen that particular issue...it's normally a problem within the control head. I have seen a few radios in the past with some broken inductors on the main board behind the control head flex strip connector, which caused various different issues. You may want to take a good look at the board in & around that area.

Since the problem rests on the main board, I would peruse the schematic and find the area that controls/routes control head inputs to the main board.

My manual isn't nearby, so I can't look for myself.

I would suspect an ASIC problem for this issue, personally.

I looked into finding a way to have the radio come up in SCAN mode. Most of the control head buttons apply a DC voltage to a couple of analog inputs to the main board. Resistor dividers are used so that a particular button sends out a particular DC voltage between 0 and +5V. You should find those analog inputs on the main board and make sure voltage appears when you press a front panel button. Then move in closer to the microprocessor or ASIC and fix wherever it stops.

As mentioned previously, there are some very small surface-mount inductors that more closely resemble rectangular ferrite beads with a piece of flat wire running through it. I had one radio with a broken one; impossible to see since it broke where the wire bent around the ferrite. It was in series with one lead going to the front panel speaker. Didn't take long to find it. I just broke the rest off and bridged it with a short piece of #30 wire running through the ferrite bead. As I recall, there are a bunch of these filters/inductors near the control head connector on the main board.

Bob M.

Well, I found the problem. It wasn't the radio or control head after all.

It was the accessory plug.


I was using a 16pin accessory plug that had a ignition sense pigtail. What I didn't realize, until just now, is that the red wire isn't going to pin 10 (ignition), it was going to pin 13 (SW B+). Since the radio powered up when +12 was applied to (what I thought was) the ignition sense wire, I had no reason to believe the accessory plug was miswired.

So I switched to the correct plug with ignition sense on pin 10 and, gee look at that, the control head changes all channels now.

And the original plug wasn't miswired in the first place, it was originally used on a Maxtrac that sent SW B+ to an external device.

*Sigh* In the end, it was just my fault for grabbing the wrong plug from the drawer.

As Paul Harvey would say: And that, is the rest of the story.....

Paul Harvey.........Good day!

Glad you found the problem and all is golden now!

Victor Xray wrote:
*Sigh* In the end, it was just my fault for grabbing the wrong plug from the drawer.

Gee...I've never done that before (hides from the lightning strike).

It's been a while since I've messed with a GTX, but I know I've hooked them up before with no ignition sense line and got full function of the radio. Is it possible to jumper or program them to require ignition sense before the keypad functions?

I believe there is an internal jumper mod to make them power up without ignition sense. I don't know the details since all the ones I've come across haven't had this mod.

No RSS programming for the GTX/LCS ignition sense...strictly hardware. The later version of the GTX & SmartNet-only LCS2000 boards (last 2-3 years in manufacture) came with a small set of micro-switches on the board, and by default they were set to allow the radio to work without ignition sense. Originally the board by default required a small 0-ohm resistor (or a wire jumper could be used) be soldered in a specific spot to enable ignition...if you had power-on with the older board, it must've had the jumper in place.

An interesting side note...the full SmartZone version of the LCS2000 never migrated to the newer board design...ignition jumper required right to the end of manufacture.