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Cobra 138 /139 alignment info?

nomadradio said:
Uniden made that radio. The same basic chassis was sold under several brand and model names. The RatShack TRC-449 is nearly identical. The factory manual is here:

https://cbtricks.org/radios/realistic/trc_449/

Everything on the main circuit board should be the same as your radio. Only the front-panel controls will be different as a rule.

73
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That manual is for a radio with digital 40 ch. readout with a PLL chip , mine is a Xtal 23 ch. with a round numbered knob and a 1/4 inch guitar mic jack . I do thank you for that link , I will need it in the future....
 
The 23-channel 138 mobile came in two versions. The first one had a quarter-inch "stereo headphone" jack for the mike, Later one had the now-standard 4-pin mike plug. One caution about that model. Don't turn up the sideband ALC. This will drive up the radio's current draw from the power supply. Once it exceeds 3 Amps the contact points in the relay will heat up. The insulation that separates the contacts will soften so that they sag, and allow both receive and transmit circuits to be active at the same time. This puts a dead short across the main power. That relay is no longer available, so be nice to it. We learned to put a current meter in line with that radio when setting the sideband ALC just to be sure we were below the 3-Amp red line.

73
 
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nomadradio said:
The 23-channel 138 mobile came in two versions. The first one had a quarter-inch "stereo headphone" jack for the mike, Later one had the now-standard 4-pin mike plug. One caution about that model. Don't turn up the sideband ALC. This will drive up the radio's current draw from the power supply. Once it exceeds 3 Amps the contact points in the relay will heat up. The insulation that separates the contacts will soften so that they sag, and allow both receive and transmit circuits to be active at the same time. This puts a dead short across the main power. That relay is no longer available, so be nice to it. We learned to put a current meter in line with that radio when setting the sideband ALC just to be sure we were below the 3-Amp red line.

73
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Thank You for the tips , I'll take any that you can throw at me , I am logging these in my notebook , The tips and manual are for a friend of mine ..... I got rid of all my SAMS when I retired from the electronics field ..... I am back into it , I have a lot of test equipment , a little more to get and I have a few manuals to get also ..... Thanks and if you come up with anymore tips I'm game ....
 
nomadradio said:
Time for Sams volume CB-57. Not much more than the schematic to see posted on the web.

73
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I found one on FleaBay , I'll scan the info he needs and mail it to him..... Thanks for the info and your time Mon Ami .... I'm on You Tube and I do live streams , in fact I got one set up now for 7 PM I go by Cajun Coin Hunter ..... The Double Eagle goin Coin is my avatar ...
 


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