Hi...
I would like to kindly request that someone whom knows the Cobra 2000GTL main circuit board inside and out, lend me a helping hand if you can afford the time to do so?
Lots of pics at (some pics are huge) : Index of /tools/pics
I use Picasa to load large pics and the zoom in and out is great and shows awesome detail.
I purchased a 2000 off of eBay and the listing stated that the unit was virgin except for a 40+ and 40- mod.
I received the unit and it looked great. Kicked ass on AM but had total modulation distortion on SSB. And also a pretty loud buzzing or hum when the mic was keyed on SSB with no audio into the mic. (this noise was heard on receiving end of another radio, not the 2000)
Reports said that the signal was very strong on SSB but the voice was worbley (that was the word used) or distorted to the point of not being able to understand it.
After doing some research and learning just a bit I opened her up for a peak.
First thing that I found was that R131 had been cut. R126 was removed and replaced with a jumper. R124 has also been removed. There are also some other areas on the board where I feel parts have been removed or otherwise messed with. These areas can be seen in the pics.
I took it to someone I know pretty well that works on radios and without the exact parts, he played with it and ended up placing a 300 ohm resistor at one end of where R124 goes and at one end of where R126 goes. This solved the humming/buzzing and over modulation problem. (also removed jumper wire)
Now... however... while the transmit audio on SSB is loud and clear, it still has a ton of outrageous modulation. (at about 20% Dynamic Mic volume)
You can hold a stock mic even a foot or so away from you while speaking in a normal tone of voice and it sounds like a bodacious D-104 with a KW behind it.
I would like to figure out what all has been done to this radio (besides the 80 channel mod and the unlocked clarifier mod) so that I can restore it back to original. I will leave the unlocked clarifier and the 80 channel mod, but I wish all power and modulation circuits to be original.
In the pics the two colored wires go to the channel mod and the red and black wires go to the Voicelock knob.
Can you 2000 experts here please look at all the pics and figure out what may have been done, that gives the still extra loud modulation? And what I need to do to make it original again?
I realize that this may be a bit time consuming so thank you very, very much.
John
I would like to kindly request that someone whom knows the Cobra 2000GTL main circuit board inside and out, lend me a helping hand if you can afford the time to do so?
Lots of pics at (some pics are huge) : Index of /tools/pics
I use Picasa to load large pics and the zoom in and out is great and shows awesome detail.
I purchased a 2000 off of eBay and the listing stated that the unit was virgin except for a 40+ and 40- mod.
I received the unit and it looked great. Kicked ass on AM but had total modulation distortion on SSB. And also a pretty loud buzzing or hum when the mic was keyed on SSB with no audio into the mic. (this noise was heard on receiving end of another radio, not the 2000)
Reports said that the signal was very strong on SSB but the voice was worbley (that was the word used) or distorted to the point of not being able to understand it.
After doing some research and learning just a bit I opened her up for a peak.
First thing that I found was that R131 had been cut. R126 was removed and replaced with a jumper. R124 has also been removed. There are also some other areas on the board where I feel parts have been removed or otherwise messed with. These areas can be seen in the pics.
I took it to someone I know pretty well that works on radios and without the exact parts, he played with it and ended up placing a 300 ohm resistor at one end of where R124 goes and at one end of where R126 goes. This solved the humming/buzzing and over modulation problem. (also removed jumper wire)
Now... however... while the transmit audio on SSB is loud and clear, it still has a ton of outrageous modulation. (at about 20% Dynamic Mic volume)
You can hold a stock mic even a foot or so away from you while speaking in a normal tone of voice and it sounds like a bodacious D-104 with a KW behind it.
I would like to figure out what all has been done to this radio (besides the 80 channel mod and the unlocked clarifier mod) so that I can restore it back to original. I will leave the unlocked clarifier and the 80 channel mod, but I wish all power and modulation circuits to be original.
In the pics the two colored wires go to the channel mod and the red and black wires go to the Voicelock knob.
Can you 2000 experts here please look at all the pics and figure out what may have been done, that gives the still extra loud modulation? And what I need to do to make it original again?
I realize that this may be a bit time consuming so thank you very, very much.
John