Transmit problem with CDM in cross band setup

[wesherman38]

Radio A CDM 1550 VHF
Radio B CDM 1250 UHF
Generic RICK
In-Vehicle Install with remote mounts. Both radio's grounded to same vehicle chassis location.

Both radio's programmed as follows: RX Audio Type: filtered Audio
Data PTT Audio Source: Ext Mic Audio
Ext. PTT Audio Source: Est Mic Audio
PIN 3: Est. Mic PTT(input) Active Low, Debounce-Yes
PIN 8: PL and CSQ Detect/Talkgroup Detect(output) Active Low, Debounce-No

The setup repeats from A to B but not in reverse.

Testing done so far: #1 +3.9VDC on pin 8 Radio B in stand-by mode
0.0VDC on pin 8 while receiving from UHF portable
#2 Ground pin 3 Radio A to chassis, radio transmits
#3 Continuity test thru RICK Radio B plug port 8 and Radio A plug port 3. 0.0ohms
#3 Directly jump Radio B Pin 8 to Radio A Pin 3. When Radio B receives Radio A DOES NOT transmit

Does anyone know possible problems with Radio A?
Since it does transmit when you place a ground directly onto Pin 3. But failing to recognize the logic low (ground) supplied to it by Pin 8 of another CDM.

I borrowed another CDM1250 VHF and put in place of Radio A, setup worked both directions. However I had to put that radio back into the ambulance, lol.
So I am back to a setup only working in one direction. Any assistance would be greately appreciated.

[Bill_G]

If it works by substitution, then you have an equipment failure.

[thebigphish]

+1.

and when you say generic RICK, you mean parts built equivalent, or something else of similar function?

[wesherman38]

By Generic RICK I mean an aftermarket alternative.

It is pretty clear there is a problem with Radio A, that I would like to get corrected, hence my post looking for further assistance.

[jackhackett]

Pin 3 just goes to a transistor with a 4.7K pull-up to +5v, pull-up normally keeps the transistor on, grounding pin 3 turns it off. Either you're not getting the signal pulled low enough or the transistor is bad.

Probably the easiest thing to try is take the metal chassis top off, pull the accessory connector out and reseat it. The connector pins actually plug into another connector on the board, maybe you've got some poor contact there.

[thebigphish]

By Generic RICK I mean an aftermarket alternative.

brand? type? vintage?

It is pretty clear there is a problem with Radio A, that I would like to get corrected, hence my post looking for further assistance.

Jack's idea to reseat the accessory connector is good, you have already identified the unit in question as being at fault when the diagnostic-by-replacement attempt. Reassign the pin in question away from the pin you are having trouble with (if you want), or have the radio serviced by someone who is capable of fixing it. You have successfully identified a hardware issue with the pin in question, try another pin...the CDM radios can have the pins assigned in CPS rather easily.

I'm not trying to be a dick, but many of us on here have a LOT of familiarity with other brands other than moto, so tersely snapping back with vague answers isn't going to get you real far. If you give more, you will get more.

[wesherman38]

Jack, great idea. Did it and now the setup works.

To bad I spent hours doing other not so great ideas.

Thanks again

[jackhackett]

Glad that worked.