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My cobra 2000 gtl

Red , I had a local stop by & look @ mine , he tells everyone one of the nicest he's seen ( he's had 4 ) said mine is a 9 1/2 out of 10 ) I have both speakers , a whole lot of work done to it , does 11w on am ( people that say they get a " lot more ) is total BS ! JMO I still want to change the meter colors & have a custom decal put on . But I did pay more than $400 :whistle: but it didn't come from Ebay . As far as antenna's i just did the same , gave a lot of my old radio's mostly mobiles away , making room in my shack ( Very Small ) for my switch box & rotor box for my new Sirio 27-4 . Besides , how much stuff can we hang on to ? Got rid of a lot & still have more ! :whistle::D 73 , Leo
 
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357magnum said:
Red , I had a local stop by & look @ mine , he tells everyone one of the nicest he's seen ( he's had 4 ) said mine is a 9 1/2 out of 10 ) I have both speakers , a whole lot of work done to it , does 11w on am ( people that say they get a " lot more ) is total BS ! JMO I still want to change the meter colors & have a custom decal put on . But I did pay more than $400 :whistle: but it didn't come from Ebay . As far as antenna's i just did the same , gave a lot of my old radio's mostly mobiles away , making room in my shack ( Very Small ) for my switch box & rotor box for my new Sirio 27-4 . Besides , how much stuff can we hang on to ? Got rid of a lot & still have more ! :whistle::D 73 , Leo
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I hear yeah man, and there’s nothing wrong with having a 2000 that is in mint condition, there’s nothing wrong with paying over 400 for a very nice one, like you have. I just hate to spend a lot of money on one, and then still having to fix it, recap it and spend even more money on it. This one dead keys 3 on am and swings to 9 lol.
 
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I’m still trying to figure out why I have no modulation on Ssb and am.

So far I have swapped out tr26, replaced r131 because it was clipped, changed c18, c109, swapped out tr23,tr25,changed out c101,

Now I have tr24 back in, if I lift one leg of r128 I get tx with modulation, I resoldered r128. Now if I unsolder one leg of r161 I get tx with modulation.
 
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Your problem may be further back towards the Output Network, where the ALC sense line starts...

Look at TR34 and it's parts...
upload_2020-2-24_8-44-51.png

IF you can key up the radio - a good clue as to know if TR34 is problematic - is with how it plays with your Mod Meter, and RF Power / S-Meter action...if it seems a little low or not very "Swingy" - then you may have isolated the problem just to the ALC circuit and it's support.

I've seen VR11 open up and suddenly change the whole ballgame.

The two "RF sense" divider bleed-down caps (the purpose is to reduce the signal strength to prevent slamming of the Base and damaging the ALC Sense) hold back RF so you can have some control using VR 11 to drive the AMC/ALC amp further up the chain. L33, C130 and C131 are used here, L33 can blow and force the transistor on all the time - check all parts in that area. As said earlier - if TR34 blew, L33 can go too - shorting itself out acxross the Base to ground and pops like a fuse...

So look around the "sense" feeder line from the output Tank circuit that TR34 uses - if you remove TR34 - check it out of circuit - if blown, you have to look further as to possibly have other caps and the bias network that are part of the "sense" and bleed-down - if they go bad, or show shorted - you have your answer.
 
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No no no!
Can't...

I'm already in cahoots with wife over what I still have downstairs...

Behind the Depends, Diapers, Latex gloves and other Anti-Coronovirus materials ...

It may never see the light of day again...

SIGH...
 
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Andy , Like said all in jest ! But I wouldn't have a problem w/ you working on my 2K . I'm lucky enough to have met a forum member on here that does & awesome job & NP's w/ him working on my equipment . He knows who he is ! :whistle:;)
 
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Red97,

when searching out bad parts remember that any semiconductor is automatically higher on your list than any passive component like a resistor or a capacitor.

it is MUCH more likely that a blown transistor or IC took out a passive than it is that a bad passive took out a transistor or IC.
yes, it happens, but semiconductors are just much more fragile devices.

so, when you find yourself narrowed down to a certain circuit or section, check the voltages of the associated transistors first before trying to measure the values of resistors and caps.
of course having good service information is key here so you'll know what "right" is.

also, when re-capping that frequency counter box, BE CAREFUL!!!

i can't stress enough just how easy it is to mess up those traces.
you may already know this, but that board is double sided and plated through, which means you can't just use solder wick. you'll need an actual desoldering iron in order to get the caps out.
if you don't get ALL the solder off of the leads, you run a good chance of pulling the sleeve out with the cap.
then you'll have to solder both top and bottom of the board to the lead to make sure the circuit works.
yes, you can keep the trace heated and pull the cap out like that, but it takes a lot of patience and maybe some good luck.
LC
 
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