CDM1250 Front Control Head

[psk31]

I have a otherwise fully functional CDM1250 mobile with a defective front panel. The UP and Down buttons are not working. The other P1-P4 buttons all function correctly, Just cant toggle through the programmed channels. I have confirmed it is the front control face by swapping over another face from a good radio. Problem followed the swapped head to the good radio.
So was wondering if anyone might have a spare front face for a 1250, or even possibly a good circuit board and ribbon cable from an otherwise defunct radio?

Kirb - VE6IV

[jackhackett]

Generally what goes wrong with them is the carbon contacts on the rubber keypad. And it's the channel buttons that go first, they start out getting intermittent and you have to push hard on the buttons, and eventually they stop working at all. There are gold plated traces on the circuit board and the carbon on the rubber buttons shorts across them, unless the board shows signs of corrosion or damage it's probably the keypad contacts. You might try looking for a NOS (New Old Stock) one. I've seen kits for repairing carbon contacts, you paint on some conductive material (I suppose one of those conductive circuit trace pens would do about the same) and I've heard of people gluing aluminum foil to the buttons (circles punched out with a hole punch). I can't say how well any of that would work or if it would eventually damage the circuit board or fall off and short something out. I'd go with a NOS keypad if at all possible and leave the hacks as a last resort.

[psk31]

I'm wondering about the option of disassembly and cleaning the keypad membrane with a bit of isoprop alcohol?

[jackhackett]

You could try it, but I wouldn't get my hopes up. I don't recall ever getting one to come back by cleaning the contacts.

[Andy Corbin]

Another thing you could try is DeOxit on a Q-tip to clean the switch components (CB trace and the button contact). All the techs I know swear by DeOxit.

Andy
W4KDN

[jackhackett]

DeOxit is good for a lot of things, but I don't think carbon contacts is one of them. Anything that gets them wet and especially oily is likely to destroy them. The circuit board contacts are gold plated and can be cleaned with isopropyl alcohol, not with anything that leaves a residue.

[psk31]

I'm confused, are you saying the cct board contacts are worth the attempt to clean (isopropyl alcohol)? It sounded like you'd not had much luck trying this as per your earlier post. I'm still thinking it may be worth the effort given the relative ease getting at the front keypad.

[jackhackett]

I was responding to the idea of using DeOxit. If you were going to clean the circuit board contacts you would use alcohol, not DeOxit as that will leave a residue that would then damage the carbon contacts.

If you want to be sure the rubber keypad is bad you could try swapping in the one from the working control head. Most likely you'll find that it's bad, at that point you can try cleaning the carbon contacts because you'd have nothing to lose, and then when that doesn't work you're left with replacing it or trying a hack. Not much else I can say.