Cobra 2000GTL Help

[longhaireddwb]

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...

 

[Quiksilver]

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

 

[IMD262]

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.

 

[Robb]

Modulation meter adjustment is VR7 from what I can find on the web...

 

[loosecannon]

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,
LC

 

[longhaireddwb]

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!

 

[loosecannon]

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.
LC

 

[longhaireddwb]

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.

 

[packrat]

Cobra 2000 is one of the very few radios that function just fine with the clarifier clipped. You just have to be mindful of the modulation setting on the radio.

 

[Robb]

...And the SWR readings are not messed up

What did you mean by that?
The SWR shouldn't have been affected by that VR7 adjustment!

Just for testing purposes:
I would check the validitiy of the SWR reading on the 2000 by running another known good SWR meter inline with the radio to the antenna and see if the SWR readings are the same between the two meters.

At least you will know if the SWR meter in the radio is close enough to trust...

 

[longhaireddwb]

I did that Robb right after I adjusted VR7 to tighten up the modulation meter. SWR readings or still the same as on my in-line SWR meter. I guess I should have worded it differently. VR7 is not adjusting the Modulation, just the Modulation meter. I'm guessing that is because of R131 being cut.

Thanks all. I've learned a lot sense I got this radio!

 

[loosecannon]

lhdwb,

just FYI, VR7 has a different function in the base station versions than in the mobile versions.
so, if you had a 148GTL or a uniden Grant XL, and you wanted to make the transmit audio louder; you would turn up VR7.

to accomplish this same thing in the 2000GTL, you turn up VR12.

the reason VR12 doesnt do anything in your radio is because R131 is cut.

if you were to replace R131 you would notice that VR12 controls your transmit audio.

also, there is no internal adjustment for the SWR meter in the 2000GTL.

have fun, that is a great radio.
LC