Cobra 142gtl

[loosecannon]

ok, the TX light isnt supposed to light when you are in PA mode, so thats all good.

the next step is to find out whether you have RF coming in, or whether the audio is being lost somewhere on the way to the speaker.

the easiest way to determine this is by using the radio's S-meter. if you see the meter moving with signals, but you cant hear them, then its an audio thing.
if you dont see any signals coming in, then its an RF thing.

if you have a parts radio, doesnt matter which type; then remove the S-meter from it, solder some 12" long wires to it, and solder some alligator clips to the wires.
then remove the wires from the 142's S-meter, and clip the alligator leads to them.
now you have an external S-meter to use for testing.

we need some way of narrowing down the area of the problem, and this is the first step.

also, with a radio this old, the electrolytic capacitors are very suspect.
if this is a radio you plan on keeping, and not just a "learner", then i highly recommend replacing all of them.
you can buy a kit on ebay for this.

heck, you may find that after replacing all the caps, your problem is gone.

one thing though, the radio will need an alignment after replacing the caps, so you'll need some test equipment eventually.
LC

 

[Klondike Mike]

Electrolytic Capacitor KIT FOR Cobra 142GTL PC 385 | eBay

 

[loosecannon]

yep!

thats the one to buy!

he even includes a couple of upgraded cap values in that kit.
well worth the money.
LC

 

[kaos513]

Thanks for everyone`s help I might just get them thanks.

 

[kaos513]

Also did noticed this radio was moded as a pbc trace was sliced a little I will post the pics

 

[kaos513]

Wierd thing yesterday i turned it on transmit stopped working but it still works on pa mode seems somewhere there is no power.

 

[kaos513]

Caps look new to me

 

[loosecannon]

what color are the electrolytic caps in the radio?

if they are light blue or grey, then they are the old originals and need to be replaced.
LC

 

[kaos513]

Some are gray some are black

 

[kaos513]

Ok here is what I did I removed the pll chip as I have a socket installed now I get my tx modulation back when I put back the pll chip I lose my modulation but also still no rf/power based on the meter.

 

[loosecannon]

dude, removing the PLL chip from a CB radio and then telling us that it brought your modulation back means absolutely nothing, except that you are misinterpreting what you are seeing.

your radio will not transmit on 27mhz (CB band) without a PLL chip in it, period.

your electrolytic caps are the original ones, and they need to be replaced.

i want to be able to help you, but if you are removing the PLL chip "to see what will happen", then im not sure i can.

troubleshooting is a systematic process that must be followed in a particular order if you are ever going to determine what the problem is, other than dumb luck. (which has been known to happen!)

i cant just follow you around your radio giving you the details of what you just tried. it wont work that way.

here are the next steps you need to follow if you want to get this radio working:

1. go to www.cbcintl.com and buy two books. "the screwdriver experts guide", and "understanding and repairing CB radios" by Lou Franklin.

2. start reading them from cover to cover, over and over again until the lightbulbs start coming on.

3. replace all the electrolytic caps in that 142GTL.

4. measure the DC voltage on each pin of the PLL chip and come back here and post them so we can determine whether or not you have screwed the radio up by attempting to operate it with no PLL chip in it.

im still willing to help you, but you have thrown me for a loop here. LOL
if you are not willing to at least try to do things this way, then im afraid that radio is destined to be an ebay special.

good luck,
LC

 

[Robb]

If nothing else, change out all of the 10v caps - at least those (about 8 of them are 10v caps/cost about ~$2-3). . .

 

[kaos513]

I will replace all caps if that dosent work like you said ebay special for parts thanks.

 

[loosecannon]

cool deal Kaos.

just wanted to say that i re-read my last post to you, and if i came off as harsh im sorry.

i just kept shaking my head when reading that you had removed the PLL chip and kept trying to operate the radio. im sure you can see how that might sound to someone. LOL

get the cap kit, some good rosin core solder (small diameter about the size of 22 awg bare wire), and a roll of desoldering braid. (the solder at radio shack is fine, but their desoldering braid sucks. use it only if its all you have available)

since its your first time replacing caps, do them one at a time. you need to pay attention to the polarity of the caps and its easier to remember doing it this way.

also get yourself a small LED flashlight that will shine a narrow beam.
you will find this invaluable for figuring out which solder traces go to which components.

use only a 25w soldering pencil if you dont have a good soldering station.
you dont want too much heat peeling the PC board traces up when you are desoldering.

oh, one more tip. coil the AC cord up and tape it securely to the back of the radio. you are going to be flipping the radio back and forth many, many times and the cord will start to annoy you. LOL

good luck,
LC

 

[kaos513]

Its not a problem we all have our days. I have been soldering since I was 8 thanks for the tip anyways I will update how I made out in the upcoming weeks thanks.