cobra 18 no tx & rx

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yamiraptor
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Joined: Thursday 17th Aug 2006, 8:32
Location: michigan

cobra 18 no tx & rx

Post by yamiraptor »

Het there guys I need your help!
I have a cobra 18 wx st
made in thailand The only other # I can find on the board are (4A1106) and under that # is 401781.
The radio has no rx and no tx. Radio turns on,has channel display,rx light is on and when keyed tx light comes on but nothing on the bench meter. The wx channel works fine. Tried different mic. Nothing. Put ext. speaker on and with volume all the way up I can hear little static. No pa. jack. I pulled voltage on the audio chip. This is what I got.

(1) 13.80v
(2) 12.47v
(3) 4.05v
(4) 8.35v
(5) 1.54v
(6) 3.46v
(7) 3.47v
(8) 1.30v
(9) 0.00v
(10) 7.03v

Any help from here would be great. Thank you Bill
timrim
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Location: Ohio

cobra 18 no tx & rx

Post by timrim »

I have repaired a lot of the 18's, almost all of them have had poor solder connections, I would check that before anything else on that radio.
yamiraptor
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Posts: 39
Joined: Thursday 17th Aug 2006, 8:32
Location: michigan

cobra 18 no tx & rx

Post by yamiraptor »

Thank you for the reply timrim. I'll go through and check for the bad solder. Is there a certain area that seems to be consistant with this problem? And would you happen to know where I can find the voltages for the audio chip. Thanks again for your help.

BILL
timrim
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cobra 18 no tx & rx

Post by timrim »

check the areas near the PLL/VCO, also pay close attention to any small circuit boards that are mounted perpendicular to the main board, those solder connections always develop problems.
yamiraptor
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Posts: 39
Joined: Thursday 17th Aug 2006, 8:32
Location: michigan

cobra 18 no tx & rx

Post by yamiraptor »

Thanks again timrim. I did a bunch of resolders with no luck so far. I'll do more tomorow. While I was at it I pulled C442,C447,C448,C529 and checked them also. All checked good. Thanks again.

BILL
yamiraptor
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Posts: 39
Joined: Thursday 17th Aug 2006, 8:32
Location: michigan

cobra 18 no tx & rx

Post by yamiraptor »

Well there Mr. timrim I have to give you a big thumbs up on this one. After going through and soldering the board and more of the board with no results. I went at the little boards then got tx and then rx after a few of the other boards. You know you look at them real close with even a 10x eye loope and they sure didn't look bad. But that proved me wrong. Thanks again for all the help. My hats off to you. Lesson learned. Have a great one and a safe and HAPPY NEW YEAR.
Bill
timrim
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Joined: Thursday 29th May 2008, 10:11
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cobra 18 no tx & rx

Post by timrim »

I am glad you fixed it. I have had so many of those radios come in and they all have the same problems.
Happy new year!
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