Batboard

Hi,

I have a CDM 1550 conventional radio that does not have any receive audio. The radio powers up but does not play any musical tones like other Waris radios do (I know it was programmed to do it - other 1550's do have those tones) and a received signal does not come through the speaker. The S-meter does show up and the receive LED does work when the signal is received but no audio. The control head ribbon cable to the main board appears to be intact and is connected along with the front speaker being plugged into the control head. After that I gave up - And nothing was connected to the accessory jack in the back of the radio.

Is there something in the programming that is not making this work or is this a hardware thing? Perhaps the amp proving audio to the speaker is dead, etc. I did not want to venture any further but is this a common issue and is there a reasonable fix?

is there a speaker in the radio?

Is it wired up??

-Josh

try connecting a speaker to the pins on the accessory connector to see if maybe it is a front-connection problems. If you cannot pull audio from the accessory connections on the back, then yes...you probably have a blown-audio circut in the unit.

Yes - I did attach a working speaker to the front panel speaker and no dice. I'm thinking the audio circuit is indeed dead.

Thanks for the info though everybody...

open the radio up and see if the jumper is in place, i think it's near the acc connector, you remove that to disable the internal speaker when you are using an external speaker. or just connect your external speaker up to the acc port and it should work.

486dx4 wrote:Yes - I did attach a working speaker to the front panel speaker and no dice. I'm thinking the audio circuit is indeed dead.

No.

me wrote:try connecting a speaker to the pins on the accessory connector to see if maybe it is a front-connection problems.

two different places.

you connected it to the same dead output that we are trying to diagnose, i am referring to the modular plug on the back of the unit that might be the audio output of choice if the internal speaker is disabled.

A couple of likely causes...
1) The audio PA is bad
2) One or both of the ferrite chokes on the outputs of the PA broke.

To check the PA you measure the voltage on the output pins of the IC, should be 6-7 volts DC on both pins, and you should be able to see the audio with a scope.

I'm not sure where the chokes are on the 1550, on a 750 they're on the top of the board near the front left side. They're a flat conductor going through a rectangular ferrite bead, vibration causes the conductor to break where it enters the bead.