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Cobra 138 XLR troubleshooting

Big Kahuna

Big Kahuna

Sr. Member
Jul 31, 2008
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Troubleshooting a garage sale find. No mods to radio, it's stock.

Found that power wasn't getting through on/off switch and voltage was low so I fixed the power issue and now it's got tx/rx but freq is off.

tp8 ch 19 showing 34.8850 instead of 34.9850 (based on alignment info for 139XLR posted on forum as I can't seem to find a service manual for this one)

Checked voltage at tp7 on ch1 and everything is correct.
 
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Maybe it’s that nefarious glue again? Just fixed a radio that was about 10khz ahead on every channel. Turned out it was the 10.240. Checked that?
 
Thanks Robb, got focused and forgot those other models used the same chassis. Going to continue poking around.
 
Ok got a little further in the troubleshooting, it's on frequency on some and off on others. And off during alignment as mentioned. Just got to figure out where in the stages the issue is.
 
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Looking at the frequency chart from the TRC-449 service manual - looks like IC7 Voltage 2A might be the issue - matches up exactly with the channels I have that aren't correct.

realistic-trc-449-sm-Page-13.jpg

3M0wgYj
 
So no voltage on pin 17 and so I decide to check the trace on the backside and sure enough wires running from the pins to the off/anl/nb switch, man I’m losing it in my old age, didn’t even see that someone had modded it.

I laughed out loud at myself....jeez. Now I can finish my alignment and I’ll have a nice operating radio :)
 
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