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My cobra 2000 gtl

R

red97k1500

Well-Known Member
Nov 26, 2012
359
291
73
texas
well yesterday I finally realized my dream of getting a cobra 2000 gtl with out having to pay stupid eBay money for it. It was practically free. I also was able to borrow a bone stock one to help put this one back to factory.Serial number 8300851. I’m 99% shure it’s a 1978 model.Since cb tricks is down, I can’t remember if it needs the service bulletin done with the zener diode.

The radio is not too bad imo, but it’s missing the frequency counter/clock module, and somebody put in what looks like a 10 dollar Chinese eBay frequency counter.

Anyway plans for it are:
Put the clarifier back to stock
Find another frequency counter/clock module
Recap the whole radio, I have 2 Klondike mike kits otw.
And also figure out why the radio has a 3 1/2 watt dead key, but has no modulation aka swing on am or side band.
And then lastly just use it and enjoy it.

I really don’t need to take any more projects,
But I just can’t turn down a 2000 gtl.
I almost didn’t start this thread, but then I thought this would be a good way to document my progress, and a place for me me to ask any cobra 2000 specific questions.
 

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red97k1500 said:
well yesterday I finally realized my dream of getting a cobra 2000 gtl with out having to pay stupid eBay money for it. It was practically free. I also was able to borrow a bone stock one to help put this one back to factory.Serial number 8300851. I’m 99% shure it’s a 1978 model.Since cb tricks is down, I can’t remember if it needs the service bulletin done with the zener diode.

The radio is not too bad imo, but it’s missing the frequency counter/clock module, and somebody put in what looks like a 10 dollar Chinese eBay frequency counter.

Anyway plans for it are:
Put the clarifier back to stock
Find another frequency counter/clock module
Recap the whole radio, I have 2 Klondike mike kits otw.
And also figure out why the radio has a 3 1/2 watt dead key, but has no modulation aka swing on am or side band.
And then lastly just use it and enjoy it.

I really don’t need to take any more projects,
But I just can’t turn down a 2000 gtl.
I almost didn’t start this thread, but then I thought this would be a good way to document my progress, and a place for me me to ask any cobra 2000 specific questions.
Click to expand...
https://web.archive.org/web/20190204091924/http://www.cbtricks.com/index.htm
 
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the tech bulletin is for the counter module that you don't have, so no worries about that one for now.

that chinese counter is probably creating noise that can be heard with the volume down.
if so, we will tackle that later on.

the way you are attaching pics doesn't allow for us to click on them and enlarge them.
if we can enlarge them we can look over the PC board for possible issues.

the way to do this is to upload the pictures to your desktop from the camera/phone (or whatever folder you usually use. i like the desktop)
then you will be able to access them using the next step i will give you.

if you look below the text box when you are creating a thread, you will see three boxes.
"Create Thread" (or "Post Reply" if you are replying to an existing thread rather than creating one)
to the right of that box is a box that says, "Upload a File".

click that box, and it will bring up a window where you can choose the pic you want to put in the thread. on the left side of this window you will see the different places you can look for your pic, depending on where you put it when you uploaded it.

you will see a list like: Downloads, Desktop, Documents, Pictures etc...
and you click on whichever one you used to upload the pic.

once you select the pic you want to upload, just click OPEN, and you will see a small thumbnail of your pic appear below the text box. click on "full Image" to put the pic in the thread.


when you do it this way, you can enlarge the pic and see much more detail.


hope this was helpful.
LC
 
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To use the chinese counters without the noise problem requires a couple of steps.

First, the board's mounting must be insulated. Can't just put a metal screw through the holes in the corners of the pc board and bolt them to a metal bracket. Those screw holes are connected to the counter board's ground circuit. We fabricate a bracket from plexiglass, and this breaks the connection between the circuit board's ground and the chassis.

The ground wire for the counter's power must be attached next to the big, fat filter cap on the radio pc board.

The power for those counters must be knocked down from the radio's 13.5 Volts or the regulator chip on the counter will overheat and fail prematurely. We use a to-220-style 7808T regulator chip. Doesn't need much of a heat sink, but this also reduces the noise leaking back into the radio's main power supply.

The input wires don't have to be changed to coax, but twisting them about one or two turns per inch can reduce the disruption to the display while transmitting.

The ground side of the counter's input doesn't go directly to ground, but has a .001uf ceramic disc cap between the wire and the circuit-board ground. This provides a path for the RF signal, and blocks any noise current from the display's digits.

You'll probably have to acquire one or more junkers to score a working clock/counter module, And then only after the 10 or 11 electrolytic caps that are in it get replaced. The temperature inside that module is higher than in the rest of the radio. This causes old age to come to those caps first in a lot of radios.

And if it were a 1978 car, finding what you need in the junkyard would be pretty routine, too.

73
 
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Well I was able to get the radio txing with modulation now, by pulling tr24. First thing I did was change c18, then through searching I found an old thread where someone’s radio had the exact same symptoms as mine, on there radio tr26 ended up being bad, so I’m going to pull it and test it.
 
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First - Congratulations!

IT's Definitely an old Phart but (to you) it is a New arrival :D

PLL DTD 1978 - looks like 29th week so the radio is in that "era" you mentioned...

Why old Phart? Well, you're going to have a recap in progress but overall it looks relatively good shape for undoing some echo/Audio mods but not sure of any TSB issues - kinda hard to tell here...

That is an oldie - and the Power supply does look like it's been changed or some work done to it. But again hard to see from pics... I see it by the "Harness pull" that some techs don't re-dress the harness back to flow along the board the best - they just pull clip and install...once done - left dangling once they remove it...

SIGH - you should be ok, but it is a work in progress.

Labor of Love - 101
 

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Thanks Andy, I’m going to a few better pictures 0f it this weekend. The radio is pretty much stock believe it or not, other than various repairs that were made to it over the years.it even still has the 8734 pll in it, so it was never channel modded. none of the switch wiring has been hacked up etc, except two yellow wires going to the meter lamps. I have already figured out how to put all the wiring back to factory. I also have a frequency counter/clock module for it, I just need a display board for it with the leds on it... if someone has one please let me know.

One thing I find odd about this radio is that someone replaced l4 at some point, but they also drilled a hole through the board directly underneath it.
 
Yes this one is a keeper for sure, I’m very happy with it, I could have payed 400 something dollars for it on eBay and still have all the same problems with it. It’s amazing the adds I see on eBay now for them. Half the time it’s a old dirty 2000 just like mine 4 or 5 pictures of it all with the covers on it. All of them listed as for parts not working. You have absolutely no idea what your getting, or even what’s underneath the covers.

I’m going to keep this radio, my old school president mckinley, 2 of my 148 gtls, and my grant xl, and a couple of my cobra 29s, and my icom ic718, and htx10... and then I’m going to try and sell the rest of my radios.I’ve come to the conclusion I just don’t need to own 15 cb radios lol. I need to put my money towards antennas.
 
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red97k1500 said:
Thanks Andy, I’m going to a few better pictures 0f it this weekend. The radio is pretty much stock believe it or not, other than various repairs that were made to it over the years.it even still has the 8734 pll in it, so it was never channel modded. none of the switch wiring has been hacked up etc, except two yellow wires going to the meter lamps. I have already figured out how to put all the wiring back to factory. I also have a frequency counter/clock module for it, I just need a display board for it with the leds on it... if someone has one please let me know.

One thing I find odd about this radio is that someone replaced l4 at some point, but they also drilled a hole through the board directly underneath it.
Click to expand...

L14 is part of the IF strip fro AM/SSB tuning - it's a single stage section that well, if you "detune" you can make it pretty deaf in AM and SSB modes - but still a workable radio - so wondering if it was a problem for them and they found a workaround for some type of bleed over interference or

Dare I say it???

Cracked a slug and had to remove the part, possibly drill it out on the bottom to back it out first, then wound up replacing it later...?

Either way, if L14 is anything from a Cobra 148/142 or even a 138 - mostly a simple IF can for the 455kHz and SSB stuff...so although critical, they seem to have replaced the part, you just have a hole in the bottom of it.

Now as far as ground traces go, they would have affected C61's ground leg which was a simple filter cap off the power supply feed to the 455kHz strip amp - not a big deal - again without much to look at I can only advise you.

I think you'll be fine. The worry is the IF strip and it's integrity but if it works now, you have little to worry about.
 
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60CEBCA5-C761-41E1-B0B6-303CC5CDA497.jpeg
Handy Andy said:
L14 is part of the IF strip fro AM/SSB tuning - it's a single stage section that well, if you "detune" you can make it pretty deaf in AM and SSB modes - but still a workable radio - so wondering if it was a problem for them and they found a workaround for some type of bleed over interference or

Dare I say it???

Cracked a slug and had to remove the part, possibly drill it out on the bottom to back it out first, then wound up replacing it later...?

Either way, if L14 is anything from a Cobra 148/142 or even a 138 - mostly a simple IF can for the 455kHz and SSB stuff...so although critical, they seem to have replaced the part, you just have a hole in the bottom of it.

Now as far as ground traces go, they would have affected C61's ground leg which was a simple filter cap off the power supply feed to the 455kHz strip amp - not a big deal - again without much to look at I can only advise you.

I think you'll be fine. The worry is the IF strip and it's integrity but if it works now, you have little to worry about.
Click to expand...

I believe your right someone probably cracked the slug then decide to replace the whole entire can. And I believe it is L4 if my memory serves me correctly

Edit: also I don’t believe the hole will cause me any problems either.it just means that this is not a Barrett-Jackson show radio with the factory chalk marks still on the firewall, this is a everyday driver that’s ment to be driven lol.The receive on this radio sounds great, it’s every bit as nice sounding as my Taiwan and philly made 148s.
 
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