midland powermax 77 250cxl issues

[Redlocklll]

Hey guys, new guy to the hobby here. I've got a Midland 77 250cxl powermax cb (top left in picture) that I'm having some trouble with. I can't get it to receive (in cb mode, squelch, volume, and rf gain have no effect) it just kinda hums and then will stop when you raise the squelch. Have also tried an external speaker, and have tried troubleshooting Mic by jumping the pins on Mic connector. It transmits fine w 1.3 swr on a cheap 36" mag mount antenna, but will not put any rx signal through speaker. Any ideas?

 

[Robb]

Hearing anything in PA mode?

 

[Redlocklll]

Hearing anything in PA mode?

Only my speech when I plug my external into the port. Theres no static or interference in pa mode. My tx is crisp on my scanner so thans no issue, just rx not working.

 

[Redlocklll]

Not sure what to check from here, other than tearing into the case and inspecting for anything burnt that's audio related. if the finals were burnt, not only would rx go out, but I wouldn't be able to tx at all though, am I correct?

 

[Robb]

Not sure what to check from here, other than tearing into the case and inspecting for anything burnt that's audio related. if the finals were burnt, not only would rx go out, but I wouldn't be able to tx at all though, am I correct?

Nope.

Are you using the stock mic?

 

[Redlocklll]

Nope.

Are you using the stock mic?

I am, but I've also tried jumping the mic tx and rx connection pins on the radio. Even then it will still tx with an acceptable swr, but still no signal rf noise.

 

[Redlocklll]

I've also taken the mic apart to inspect wiring or if it was sticking some, but it all looked pretty clean in there.As well took the mic cord connector apart to check for wear but again, appears fine.

 

[Robb]

RF Gain all of the way up, and Squelch all the way down?

 

[Redlocklll]

RF Gain all of the way up, and Squelch all the way down?

yessir. and I have a cobra 19 ultra lll hooked up now that works so the coax is fine as well.

 

[Robb]

Tried an external speaker?

 

[Redlocklll]

Tried an eternal speaker?

I have, a speaker, headphones, and the aux input on my stereo. same thing. it sends the hum through all of those as well so its not the speaker. its a very faint hum, but as soon as you adjust the sq, it goes away and just silence.

 

[ExitThirteen]

Sounds like a bad capacitor around the audio IC. That is a 30+ year old radio, and the electrolytic caps can be suspect at that age.


~Cheers~

 

[Robb]

Sounds like a bad capacitor around the audio IC. That is a 30+ year old radio, and the electrolytic caps can be suspect at that age.


~Cheers~

Hey Xit; what chassis does this thing use?
Cybernet?
Thnx . . .

 

[Redlocklll]

Sounds like a bad capacitor around the audio IC. That is a 30+ year old radio, and the electrolytic caps can be suspect at that age.

Well I'll tear her apart tonight to see if anything looks burnt and go from there. I'll shoot up some pics if I have any troubles locating it. Thanks man.


~Cheers~

 

[Redlocklll]

Hey Xit; what chassis does this thing use?
Cybernet?
Thnx . . .

This is what the radio looks like