The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Just got this one tonite, cm-10, channels expanded. It had a 2sc1969 final in it and wasn't tx'ing. Put the factory final back in , aligned and it TX's great and on freq. every channel. But it has no tx... tried keying radio beside it - both on antennas, and no recieve...

Thanks in advance for any help with this one!


Update: when cold - sitting overnight - when powered up it RX ok for about 5 minutes then fades out as the 3 ic mounted to the frame warm up...audio chip - a 7808 and a 1366

I found a cold solder joint, pin 3 of the audio chip, touched it up and seems to be fine now...



OOOPS, spoke too soon when it fades out, I can cool IC 201 (listed as the FM demod) and RX comes back.....Just a bad chip or a bad voltage input? anyone have specs on this? (10930 A55)

One other question, this radio has had the extra channels added, but it also has had the FM band cap removed to allow the am/fm band select to work, but I do not notice any difference in audio like on a Ranger 2950... Does this mod really do nothing? The audio chip is a K1A7217AP which is a fm capable chip? Possibly just the other components aren't on the board? Any thoughts?

Thanks again to the forum and those who help us "garage" cb techs!!!

IC201 is a TK10930 made by TOKO Japan, it is an AM/FM IF Detector, the AM output in on Pin 13 and Pin 12 is FM output, Pin 14 selects AM when grounded and FM when open. It is common to see this chip fail, check supply current it should be about 7ma also check the squelch is working as this will kill the audio.

I do not have a diagram of this radio so this is the bast I can offer.

Rick.

Thanks for the input Rick!

Audio chip is ok, squelch works correctly too.

The best source I found for schematics is here:
http://malzev.tripod.com/cb-funk/m-3000.htm

By looking through there you can find the alignment chart, theory of operation, flow chart and a location schematic. However no voltage references...

This radio is gonna be a wierd problem I'm sure, I unplugged and left it off while I worked on a 148, plugged it back in and it worked about an hour then faded away... But still no difference in audio between am/fm select when it was working. I'm not really worried about the FM, it isn't used very much here in the states....

I am away until Monday next week I will have a look over the diagram when I get back.

I have found some more info on my good old mate Bennie site, try this link www.cbtricks.com/radios/cherokee/cm10/index.htm

Rick.

Check IC201 pin 4 it should be about 7.8 to 8 volts and pin 10 it should be about 4.2 to 5.5 volt. Check the voltages before the audio fades out and after the audio fades out. Also check the output of IC303 which is the 8 volt regulator. Lets us know how you get on.

Rick.

Thanks again Rick, IC 303 was heating up, cause was a shorted resistor, Just finished this one.... Had it on the shelf for awhile!