• You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Constant loud squeal when I turn on my Cobra 2000GTL radio

loosecannon

Sr. Member
Mar 9, 2006
4,213
3,632
273
I already have. I thought I wrote that in the first post.

There might be two bad microphones. I doubt it but I'll give it a shot trying the jumper. Besides I'm learning more troubleshooting procedures and I do like learning things.

it's not about the mic being "bad", just not wired for that particular chassis.

if one of the ground pins is connected to the audio wire because the mic is wired for another radio then you will get this exact problem.
LC
 

ShakyMcQuiver

Member
Apr 11, 2018
40
26
18
The best solution to fix your radio is ship it to me... I'll take it,,, sight unseen... unburden yourself with the problem... ROFL.... (YES I'm joking!) :)

Kidding aside...

Welcome to the board! I'm also a Padawan on this site. Good people here with about a billion years of combined radio experience. I'm sure they will help get your radio fixed up and running soon.

Back to the subject...

I'm also restoring my Cobra 2K and I ran across a similar post the other day. His squeal turned out to be something with the headphone jack and its plastic bushing? If I recall, it had slipped or broken and was shorting something. You might take a peek there.

Is there any evidence the mic jack has been re-wired? I can't count how many hours I've spent chasing down a short when it ended up being a tiny SINGLE sliver of 'disappearing' no-seeum wire! Of course it doesn't help the older (and more blind) I get :( .

ShAkY
 
  • Like
Reactions: SmilinDoug

SmilinDoug

New Member
Aug 27, 2022
18
4
3
62
still waiting on the jumping of pins 2&3 of mike socket for the results
I did that, bridged pins 2 and 3 and I still got the noise. With the mic disconnected there was nothing, which is right. So I'm sure the mic is wired correctly.
 

SmilinDoug

New Member
Aug 27, 2022
18
4
3
62
The best solution to fix your radio is ship it to me... I'll take it,,, sight unseen... unburden yourself with the problem... ROFL.... (YES I'm joking!) :)

Kidding aside...

Welcome to the board! I'm also a Padawan on this site. Good people here with about a billion years of combined radio experience. I'm sure they will help get your radio fixed up and running soon.

Back to the subject...

I'm also restoring my Cobra 2K and I ran across a similar post the other day. His squeal turned out to be something with the headphone jack and its plastic bushing? If I recall, it had slipped or broken and was shorting something. You might take a peek there.

Is there any evidence the mic jack has been re-wired? I can't count how many hours I've spent chasing down a short when it ended up being a tiny SINGLE sliver of 'disappearing' no-seeum wire! Of course it doesn't help the older (and more blind) I get :( .

ShAkY
I checked this and tried a different mic, it was the same thing, no help. Thanks for the advice though.
 

SmilinDoug

New Member
Aug 27, 2022
18
4
3
62
Did you ever try the screwdriver-tip test, bridging it across pins 4 and 5 of the mike socket? Like in the picture.

That test could reveal quite a bit.

73
Now I'm confused. LOL I thought I was supposed to bridge pins 2 and 3. I'll go up to Dad's and try pins 4 and 5 next.
 

SmilinDoug

New Member
Aug 27, 2022
18
4
3
62
here is a pic of c172 1000uf View attachment 60493
This is great, but what I've been looking for and really need is the board layout of the bottom of the circuit board. I've got a 16volt 1,000uF cap for testing and I think I got the right solder points. The points I tested I ended up getting the same squeal. I'm hoping I got the wrong solder points. I hate to bother you but could you post a pic of the bottom of the board, and point out the cap. I really appreciate the help you guys are giving me. I did find a board layout at CBTricks but that was only on the top like your pic.
 

1iwilly

Well-Known Member
Dec 7, 2008
553
318
73
60
ok here the 2 black dots are the spots for the C172 solder side when you remove it the board you will see the + to put it back the same way also IF that doesn't fix it can you unplug the frequency counter to see if it goes away cause you say squeal but it might be a loud hum is there a way you can record it and upload the wave file???
i have my second 2000 with covers off as i was fixing a bad channel segment and i can send whatever pic you need moving forward the second pic is the power source for the frequency counter20220908_181149.jpg
 

Attachments

  • 20220908_181327.jpg
    20220908_181327.jpg
    3.3 MB · Views: 5
  • Like
  • Love
Reactions: SmilinDoug and NZ8N

SmilinDoug

New Member
Aug 27, 2022
18
4
3
62
ok here the 2 black dots are the spots for the C172 solder side when you remove it the board you will see the + to put it back the same way also IF that doesn't fix it can you unplug the frequency counter to see if it goes away cause you say squeal but it might be a loud hum is there a way you can record it and upload the wave file???
i have my second 2000 with covers off as i was fixing a bad channel segment and i can send whatever pic you need moving forward the second pic is the power source for the frequency counterView attachment 60532
Thank you very much. I really appreciate this.
 

SmilinDoug

New Member
Aug 27, 2022
18
4
3
62
ok here the 2 black dots are the spots for the C172 solder side when you remove it the board you will see the + to put it back the same way also IF that doesn't fix it can you unplug the frequency counter to see if it goes away cause you say squeal but it might be a loud hum is there a way you can record it and upload the wave file???
i have my second 2000 with covers off as i was fixing a bad channel segment and i can send whatever pic you need moving forward the second pic is the power source for the frequency counterView attachment 60532
Those were the points I was testing with the capacitor. I also unplugged the frequency counter and still have the noise. I'm gonna end up scratchin' a hole in my head tryin' to figure this out. LOL
 

SmilinDoug

New Member
Aug 27, 2022
18
4
3
62
Did you ever try the screwdriver-tip test, bridging it across pins 4 and 5 of the mike socket? Like in the picture.

That test could reveal quite a bit.

73
I tried bridging pins 4 and 5. It does transmit, and of course the noise goes away when it transmits.
 

dxChat
Help Users
  • No one is chatting at the moment.
  • @ ButtFuzz:
    GR&T Super MC-11/A Crystal Synthesized and is in SAMS #22 I have no further information on this radio.
  • @ Robert Dinsmore:
    I have schematics and Manuals I need someone to work on it
  • @ Robert Dinsmore:
    I have a MC-7 as well W D-104!
  • @ Robert Dinsmore:
    does anybody have any Ideas for working on a General MC-11A