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hacked up cobra 2000

dozerman

dozerman

hello, its me again
Dec 16, 2013
186
36
38
milan tennessee
ok, i recently got a cobra 2000 that can be compared to one of those "buy here pay here" car lots. its obviously been through a dozen hands, been modified by each and has been rode hard and put up wet. ive been able to undo all the "mods" except for one. talkback. ugh.. this variation has speaker wire that, in the back, has one lead tied to c192 and the other to the speaker 2 ground. following the wire to the front panel, it is tied to an on off switch. that was neatly drilled into the front bezel. (please note my sarcasm throughout, as i despise anything that takes away from stock appearance) now, i thought i could simply unsolder the wires in the back and be done with it. nope. when i do, i have zero key up, zero modulation. when the switch is flipped, its the same. i thought moving it to the PA jack would work, allowing key up. nope. it only works on the speaker outputs. if i take it off, i have nothing. what in the world is doing this?
 

I believe Nomad has it nailed, but i believe there might be more than just a bad connection from pin 4 of the mic jack to PC board ground.

look at this schematic:
http://www.cbtricks.com/radios/cobra/2000gtl/graphics/cobra_2000gtl_om_main_sch_11x17.pdf

now look specifically at SP2 over on the right side of the schematic.
notice that the shield for this jack connects to L417 (could be just a ferrite bead slipped over the wire, or it could be an actual coil, im not sure).

the dotted lines represent smaller PC boards. PC-479 is the one for the speaker jacks, and PC-480 is for the headphone jack on the front.

follow the wire from L417 out of PC-479 and on to PC-480. you will notice that this wire link connects also to pin 3 of the mic jack, which is grounded on RX.

Your talkback mod simply moves the speaker ground connection from a place that was only grounded on RX to PC board ground.

if you look at C192 on the schematic, you will see that it is just a bypass cap going from
PC board ground to chassis ground. the talkback wire would have been soldered to the PC board ground end of C192.

so, you have to re-attach the original wire link after you remove the talkback wire to ground. This wire may still be present in the radio but might be de-soldered at one end or both ends.

if you replace this wire like the schematic shows, and confirm that pin 4 of the mic jack does indeed connect to PC board ground, then you should be good to go.
LC
 
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Well can get new decals and if you fill the hole and put a new vinyl graphic over it could the hole be covered? Sometimes you have no choice but to add a whole but where and how you do it can make a huge difference. Not all radios have convenient switches that can easily be repurposed. In this case why they did not use the back of the radio to maintain stock appearance or repurpose an existing switch is beyond me. Ignorant people do a lot of stupid impulsive things. Impulse control is usually missing or absent in these types and in serious criminals. The only marker worse than lack of impulse control is lack of empathy!

I would have cheated and stuck another board in like a Cobra 148 GTL board and taken my time fixing up the stock board. LOL Lack of impulse control I guess! LOL

I was going to say the same thing that Nomadradio said.....LOL Losecannon made a great point.
 
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ok fellas, im back on the 2000. i did as suggested @loosecannon @nomadradio , and printed that schemo when i started this unwhacking. last night i took the mic jack out and re wired it according to the schematic. pin 1 to dynamic. pin 3 to the speaker jack in the back. pin 4 to chassis ground. pin 5 to the cb\pa switch. and pin 2 to ground. nothing. i rewired the mic in case i messed it up, still nothing. no rx or tx. ive got some other wires to track down as well. the morons put channels in it, and neatly drillled two holes for switches in the front. they clipped some of the wires on the clarifier, and ive got one coming from the speaker switch up front that goes no where. ive got one of my 1000's open comparing wiring. not all of it wire correspond but maybe it will get me in the right direction. thanks thus far for yalls help
 
Onelasttime said:
Well can get new decals and if you fill the hole and put a new vinyl graphic over it could the hole be covered? Sometimes you have no choice but to add a whole but where and how you do it can make a huge difference. Not all radios have convenient switches that can easily be repurposed. In this case why they did not use the back of the radio to maintain stock appearance or repurpose an existing switch is beyond me. Ignorant people do a lot of stupid impulsive things. Impulse control is usually missing or absent in these types and in serious criminals. The only marker worse than lack of impulse control is lack of empathy!

I would have cheated and stuck another board in like a Cobra 148 GTL board and taken my time fixing up the stock board. LOL Lack of impulse control I guess! LOL

I was going to say the same thing that Nomadradio said.....LOL Losecannon made a great point.
Click to expand...


yeah i love a stock look. i hate anything that sticks out. i may have to go the decal route though. ive seen on that one social media vacuum, some customized bezels on another 1000. the guy had re-purposed some switches and knobs and it looked totally stock. i tried asking the dude where he got it and was met with a "mind ya business" kinda attitude. even carries over to my amps. i love those trashy Maco's. i have a bunch of them. each one gets taken back to stock cosmetically with paint and stickers. underneath, im still trying to get the hang of all that. re-wiring and replacing parts is easy. diagnosing is another story. i wish i had a tube tech around me i could study under and pick their brain. but those guys are going the way of the dodo, and not passing things down. lol well that was a tangent, my apologies
 
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Just a note on cosmetic mods to vintage radios. You need to keep in mind that these things weren't always classics, at one time they were just old used radios.
 
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StrangeBrew said:
Just a note on cosmetic mods to vintage radios. You need to keep in mind that these things weren't always classics, at one time they were just old used radios.
Click to expand...


oh yeah thats for sure. but, with the majority of any radio ive owned, ive always kept stock appearances. old and new rigs. a lot of folks dig that "customized" look i guess, and dont mind making it their own so to speak. its just a headache for silver screwdrivers, not gold status yet, like myself to reverse engineer lol. really glad folks here dont mind sharing knowledge
 
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My 2k is modded looks Great and yes it's one of those !lol Btw as said when this model comes up in other posts , I did not purchase it directly from him or have him " Mod " it I bought it used and performs flawlessly .JMO
 
357magnum said:
My 2k is modded looks Great and yes it's one of those !lol Btw as said when this model comes up in other posts , I did not purchase it directly from him or have him " Mod " it I bought it used and performs flawlessly .JMO
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I'm glad yours does! This one, on the other hand, doesn't. I never was a fan of the 2000 but I figured I would try one. I'll stick with my 1000's. Looks a lot like one, but half the headaches. But it's another diagnostic teaching tool for me. Gotta learn the hard way I guess. Will get back on I think tomorrow, been watching the new Thor movie with my daughter tonight.
 
Well I've got audio, recieve am fine key up now. The output is pretty dismal. About 9 pep at 80% modulation. Ive replaced the am regulator and pre driver, adjusted bias and peaked the tx chain. Am waiting on a new driver and final. Odd thing is I still have talk back. With an external speaker, it's still loud. And there is a buzzing sound when I key up. I'm guessing something isn't oscillating?
 
dozerman said:
Is oscillating. Damned predictive text..
Click to expand...


Well I got fed up with trying to figure out the wiring on the 5 pin from what was in here, sooo I took It out and put a 4 pin in it. Works like a charm. Also did an "npc" to the radio that I found online. Figured I would try it, not much to lose on those unit lol. It did surprisingly well! From a key low enough to just register a frequency, it swings 17 pep and has loud audio on a stock mic. Still gotta figure out why when I plug a turner mic into it, the rx diminishes slightly. But it hasn't no talkback no way thank the lord. Thank for everyone's input!
 
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That radio has been played with , If I plug my Turner SSK into mine and go past !11 o'clock receive starts to distort ( No Need for over @ 120 percent modulation anyway ) Mine is fine below 11 o'clock . Yep someone's been in there , does it have a so called swing kit also ? Mine is 1-11 on am if anyone tells you they are getting more than that on a Cobra 2K , unless finals have been reworked I call BS on that . And this is just my opinion .
 
357magnum said:
That radio has been played with , If I plug my Turner SSK into mine and go past !11 o'clock receive starts to distort ( No Need for over @ 120 percent modulation anyway ) Mine is fine below 11 o'clock . Yep someone's been in there , does it have a so called swing kit also ? Mine is 1-11 on am if anyone tells you they are getting more than that on a Cobra 2K , unless finals have been reworked I call BS on that . And this is just my opinion .
Click to expand...


It had a "swing kit" in it, but the output was dismal. I replaced the stock parts and did the NPC for the 2k. Only reason I'm getting about 17 pep is I volted the final. I took the 1969 that was in it out, and put a used 2078 in place. But the differences in the audio reports was worth the effort. It's as unhacked as this golden screwdriver can get it. But it still not too bad.
 
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