cobra 148gtl no rx audio

speedracer6g · Post by **speedracer6g** » Saturday 20th Sep 2008, 1:08

This radio has transmitt and no rx. the needle moves with rx but no audio. I checked the audio chip and it is fine I injected a signal into it and i have audio on the speaker. I checked tr13 and tr12 and the voltages are as follows.

TR12 B 0V, C 8.19V, E .72
TR13 B 8.24, C .66, E 8.24

I also checked voltages on mb3756 IC and they are all spot on. Any help or ideas would be appreciated.

thanks,

MIKE

speedracer6g · Post by **speedracer6g** » Saturday 20th Sep 2008, 1:11

I also checked tr43 and there is 0v on all legs on tx and rx. Also the pcb # is PC-412

http://www.youtube.com/user/TheDefpom · Post by **The Defpom** » Saturday 20th Sep 2008, 11:18

If you have an audio probe I would suggest you connect it to the volume pot and see if audio is at that point.

Things to check:
C186
C72
Volume pot
TR19

speedracer6g · Post by **speedracer6g** » Sunday 21st Sep 2008, 4:24

I Injected audio befor the pot and everyting works from the point. It seems like the audio is muted or squelced up but cant find where thing are fudged up. transmit works fine. when i put rf into the radio via my service monitor with 1kz tone i get receive on the meter but no sound. I will check the thing listed above and let you know how i make out.

thanks,

MIKE

timrim · Post by **timrim** » Sunday 21st Sep 2008, 6:16

Sounds like the squelch amp may be bad, I will take a look at the circuit when I get to work.

speedracer6g · Post by **speedracer6g** » Sunday 21st Sep 2008, 6:18

SWEEEET

thanks Scott for the tip I will have to put that one in my notes. It was c186 by the audio chip. Must of been shorted out I replaced it and it is all good now.

thanks again,

MIKE

http://www.youtube.com/user/TheDefpom · Post by **The Defpom** » Sunday 21st Sep 2008, 6:31

Glad I could help.