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Cobra 2000GTL Help

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  #1  
Old 02-04-2010, 06:24 PM
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Default Cobra 2000GTL Help


I got this 2000 and after a bunch of funds out of my pocket it now works. The problem I'm having now is that the modulation meter pegs hard when I'm talking. I can't seem to find an adjustment to this meter.

Can anyone point me in the right direction to turning down the sensitivity of this meter? If there's no adjustment then I'd be willing to put in a resister in the right place if I could find someone to tell me where the right place would be.

BTW, The limiter has been cut! Could this be part of my problem? Well, R131 has been cut which I understand opens up the AM side but not the SSB side. I keep the mic gain down to just under distortion but the meter still pegs hard. I'm afraid it going to break!

This meter is also the SWR meter when you flip the switch but I don't want to throw the SWR way off.

Help...
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Last edited by longhaireddwb; 02-04-2010 at 06:48 PM.


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Old 02-04-2010, 06:52 PM
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I would find a very reputable tech that specializes in the 2000's and have him/her check it out. Cutting the limiter is a no-no on these rigs. I would not take it back to the person you donated your hard earned money to.
Rogerbird is an expert on the HR2510 line,and he's from your area. Maybe he knows a Cobra tech in that area.
JMO

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Old 02-04-2010, 06:55 PM
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Quote:
Originally Posted by longhaireddwb View Post
I got this 2000 and after a bunch of funds out of my pocket it now works. The problem I'm having now is that the modulation meter pegs hard when I'm talking. I can't seem to find an adjustment to this meter.

Can anyone point me in the right direction to turning down the sensitivity of this meter? If there's no adjustment then I'd be willing to put in a resister in the right place if I could find someone to tell me where the right place would be.

BTW, The limiter has been cut! Could this be part of my problem?

Well, R131 has been cut which I understand opens up the AM side but not the SSB side. I keep the mic gain down to just under distortion but the meter still pegs hard. I'm afraid it going to break!

This meter is also the SWR meter when you flip the switch but I don't want to throw the SWR way off.

Help...

I think you answered your own question.

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Old 02-04-2010, 06:59 PM
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Modulation meter adjustment is VR7 from what I can find on the web...
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Old 02-04-2010, 07:07 PM
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i think Robb is on the right track.

in some MB8719 radios, like the cobra 148GTL and the uniden Grant XL, the AMC adjustment is VR7.

HOWEVER!!!

go to the base station models of either of these radios and you will find that VR7 controls the modulation meter adjustment.

in the cobra 2000GTL, the AMC adjustment is VR12, or cut R131 and use the mic gain on the front of the radio as the AMC.

on the president/uniden madison, there is no AMC adjustment. just a fixed resistor (R130 in holes marked for a diode) with a value that keeps the modulation under 100%.

most likely, someone used the tune up info from the 148GTL to tune up your 2000GTL and turned VR7 all the way up looking for more modulation.

Set VR7 so that when you say "ahhh" into the mic, with the mic gain all the way up; the meter moves almost all the way to the right.

then when you set the mic gain where you like it, (best is between 12 and 3 o'clock IMO) you will not be pegging the needle.

good luck,
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Old 02-04-2010, 07:47 PM
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Thank you all for the quick response. I will give VR7 a try. And then VR12 if I can't find VR7. And as you said Loosecanon I like the mic gain around the 2 o'clock position myself. Lots of modulation and just under the distortion. Ill let you all know how it turns out. I'll dive in right now!
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Old 02-04-2010, 07:54 PM
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if R131 is cut, turning VR12 will not have any effect, as it is effectively removed from the circuit.

as for where to set VR7, if you have an external modulation meter, you can set the mic gain on the radio so the external meter reads 100% and then set VR7 so the internal meter reads the same.

VR7 is located just in front of the main filter capacitor C172.
just to the right of L6.
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Old 02-04-2010, 08:03 PM
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OK, I don't have any clue what VR12 does! It don't control modulation, SWR, Watt meter, Modulation meter, Freq. I just put it back where it was!

I adjusted VR7 and now my meter needle quit bouncing off the far side! Much better! And the SWR readings are not messed up. Just what I was wanting. Thank you all for the help.

This has to be the fastest question, answer and fix ever on the forum!

1hr 39min.
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