CDM1250 low pwr out but works fine in service mode.

[cbroseinak]

Have a CDM1250 VHF Hi power that produces about 10watts. When I use service tuning software and check the radio power level settings it produces the correct power levels, but when I back out of the tuning software saving everything, its back to 10watts. Bench supply and cables are fine as any other radio tested produces correct power levels.

What gives?

[jackhackett]

Inside the radio there's a rubber piece with carbon contacts on it that's supposed to disable the PA when you have the chassis taken apart, make sure that's seated properly. Also you could check the PA bias and current limit settings. And, is it programmed outside of it's normal frequency range?

[cbroseinak]

Programed with-in its operating range. The rubber piece with the carbon contacts is now bad...I tried to clean it. But before the cleaning attempt, with the cover off and heavy pressure on it I was only getting a couple of watts, well below the 10watts I was getting. After cleaning I only got about a watt or so.

Can I just solder across the zig-zag connects instead of relying on the carbon pad? This radio is not worth putting money into it. If I can get the 10watts or so out of it thats enough for what it has to do. Bugs me it will do well over 40watts in the service tuning software but only 10watts in real world. I guess I could get into it further and figure out the PA bias and current limit settings, but i'm a parts replacer...not a tech, sad but true.

[jackhackett]

Oh.. yeah.. you don't generally want to try cleaning carbon contacts.
You could try jumping the zig-zag contact.. if you can, do it away from the actual contacts, like on the circuit trace leading to them. You'll still need to have that rubber piece in there though, it presses the PA transistor against the heat sink.
The bias and current settings are tricky, and the documentation isn't very good. If you don't know what you're doing you could mess it up for sure, so you'll probably want to leave that alone.

[cbroseinak]

Ok, thanks. Performed work as recomended and its doing its thing. Actually doing a bit better with the solder connects than with the rubber carbon pad, getting 13+watts now instead of 10+watts. Calling it "good" till it bites it totally.