142 GTL

[Wrench]

I just got a !42 GTL, it has not been unlocked, or otherwise messed with.
The only thing wrong, is I get a LOUD squeal when I key up. Watts and modulation almost smack the corner, But SWRs are fairly flat, when I turn down the Dynamike. I am using the stock mic, nothing else.
I'll bet it is something simple, maybe an old cap.
What do you guys think? This thing looks like new!

 

[Needle Bender]

Sounds like you've got a short in the mic relay, or possibly inside the radio's TX/RX switching circuit. First try a different mic, after you make certain it's not stuck on PA.
Do you have an external speaker? Is it plugged into the speaker out put or the PA output jack?

 

[Wrench]

Sounds like you've got a short in the mic relay, or possibly inside the radio's TX/RX switching circuit. First try a different mic, after you make certain it's not stuck on PA.Do you have an external speaker? I sit plugged into the speaker out put or the PA output jack?

Ok, I tried a differerent mic, first. No dice.
The one mod I saw, that can cause this, is that there is a resistor soldered to the PA and output speaker jacks. (idiot talkback) The squeal goes away, if I use an external speaker, as I was going to, anyway.
The only problem now, is if you turn up the Dynamic all of the way up, it has a fast repeating squeal, so I will pull the Dynamic pot and check it out. It may not be the right one, or defective.
I would like to keep the talkback, to check the echo pattern after I install the echo board. And yes, no Roger Beep, they annoy me!
Thanks! You got me on the right track.

 

[johne2hotty]

you need a 3 switch mic. for that radio a d-104 tug or tup 9 stand that sounds like your problem i could be wrong but thats what it sounds like is the matter a 2 switch mic will do what your saying the trouble is

 

[Needle Bender]

Thanks! You got me on the right track.

I gotta get lucky sometime!

 

[Wrench]

I'm using the standard Cobra Mic, and so is the one I substituted.
Now, it only makes the noise if the built in Dynamike, witch is a mike gain, is turned up all of the way. I'm thinking a capacitor is dried out, it works OK, otherwise. The pot seems OK, but the On/off pot is getting replaced when I get home from work. It is scratchy, due to age.
I really don't think it is a mic problem anymore. I will remove the resistor used for the talkback, and put in a talk back kit.
At least I can use it.

 

[Lefty]

Howdy Wrench,

First off I'd get rid of that f**king talkback resistor, that's the dumbest mod ever.
Next check to see if R104 has been cut or removed, if so fix that mistake. R104 is the voltage source for the AMC (Automatic Modulation Control), removing that can cause the audio to overload.

If you have one, run a D-104 on the 142 and go through the alignment precedures. They can be found on a Google search or in Sam's Photofacts. I did that to mine and it works great. Am (I don't run that much anyway) will do 4W DK and swing to about 6-7W, on SSB it will swing up to 15-18W easy. Trying to get much more than that will have no real net value, get it within specs and clean and that puppy will talk.

Also check out the power supply (especially if it shows backwards modulation on AM), crank up the voltage to 14.8V.

I have a copy of the alignment procedures if you want.

Good luck es 73!

 

[Wrench]

Howdy Wrench,

First off I'd get rid of that f**king talkback resistor, that's the dumbest mod ever.
Next check to see if R104 has been cut or removed, if so fix that mistake. R104 is the voltage source for the AMC (Automatic Modulation Control), removing that can cause the audio to overload.

If you have one, run a D-104 on the 142 and go through the alignment precedures. They can be found on a Google search or in Sam's Photofacts. I did that to mine and it works great. Am (I don't run that much anyway) will do 4W DK and swing to about 6-7W, on SSB it will swing up to 15-18W easy. Trying to get much more than that will have no real net value, get it within specs and clean and that puppy will talk.

Also check out the power supply (especially if it shows backwards modulation on AM), crank up the voltage to 14.8V.

I have a copy of the alignment procedures if you want.

Good luck es 73!

Yeah, i clipped the talkback resistor a minute ago. I am going to run a Turner +3, that I had on another 142 years ago. It works on my 148 real well.
I got it with that talkback resistor, it seems you need a capacitor in the "circuit: somewhere, but there are kits that wpork without problems, and can be switched off.
My voltage is at exactly 14 volts, no backwards mod. I set it to key at 2 watts, and it will do 10-15 on AM, if you talk loud. The =3 would keep it up there. I'll check the R104 afterwork.
Thanks for your input, so I can get some output!

 

[Lefty]

Cool, and I hope you get it back up 100%.

I'm a huge fan of the 142, have 3 of them that I'm restoring from bad mods and sloppy workmanship.

Going good so far, just need to find a good S\RF meter for one of them.