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Cobra 29 alignment ... can't adjust to 27.185 with L24

1jonnyz

1jonnyz

Member
Dec 30, 2011
62
3
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Having a problem aligning this 29... I am trying to align the TX and the lowest I can get with L24 is to 27.191, the slug is all the way to the top when I get down to that frequency. Not sure what the problem is. This radio has a bunch of mods done to it, not sure what all of them are. Any help would be much appreciated!
 

if you can upload a pic of the inside of the radio it might help some of the members on here identify what some of the mods are.. if it has been modified to the hills you may be SOL and need to take it to a certified tech
 
No Robb, someone put an echo board in it and used the Delta Tune for that. It has a 1969 final and I am pretty sure the super modulation "kit". I think the guy said R&R in Claymont DE did the work on it. The owner of this radio said it was drifting off channel, where every so often he couldn't understand people on 19 and he would drop to 18 and said he could hear them fine then. I told him I would take a look at it.
 
1jonnyz said:
No Robb, someone put an echo board in it and used the Delta Tune for that. It has a 1969 final and I am pretty sure the super modulation "kit". I think the guy said R&R in Claymont DE did the work on it. The owner of this radio said it was drifting off channel, where every so often he couldn't understand people on 19 and he would drop to 18 and said he could hear them fine then. I told him I would take a look at it.
Click to expand...

what happened to the Delta Tune control is it just stuffed in there?
 
The Delta Tune is gone. I do see on the schematic that D17, which is part of the Delta Tune circuit, has an 8.2K resistor on the anode side. Not sure what that's about??
 
I just checked another 29 I have sitting around and found where the 3 wires from the DT go. The wires have been removed from this radio.
 
Check the freq at each xtal (one for the PLL and the other for the Osc circuit), as someone pointed out the xtal already as a potential problem. Xtals can go bad every once in a while. Not that uncommon. They use cheap xtals to begin with; so checking them is required . . .
 
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Ok, I was checking voltages on IC1... I was getting no voltage on pins 1,4, and 5. I moved the ribbon cable going to the channel switch a bit and suddenly had voltage. I touched up all of the pins on the ribbon cable and now I dialed 27.185 in with no problem!
 
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Now you know why the owner said it drifted off freq now and then. It was an intermittent connection causing the grief. Most times the problem is something simple except when it's not. :)
 
While I have you on here Captain... what is usually the cause for LED segments not working on the channel display? I have several radios around here with that problem.
 

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