Cobra 2000 modulation meter repaired

[BBB]

When I got a Cobra 2000 a few years ago the Modulation/ SWR meter was stuck in the middle. I figured the meter's movement coil was still good as the meter would try to move once and a while.

I decided if it was bad and needed replaced I would pull it out and dissect it to see what failed. I have heard that there is a bearing pre-load adjustment on some meters. Sure enough, I backed out the super tiny front brass screw just enough to free up the meter movement. Now it's back in action.

If you back out the screw too much as I did at first haha, the horizontal movement axle pin will pop out of the brass bearing. Don't worry as you can carefully guide it back into the bearing. The needle return spring is very fragile so take your time re-inserting the pin.

To remove the meter, there is a sheet metal retainer behind that has two screws in it. I was able to use a long Phillips screwdriver to get at them. Un-solder the meter leads and remove the meter. The front clear plastic cover is simply scotch taped to the back of the meter from the factory. Then you can get at the front bearing screw. There is a bearing screw on the rear as well but I have not had luck adjusting this screw on meters for some reason. There is also a meter needle centering fork adjustment on the rear of the meter accessible thru a slot if you need to set the meter at zero.

If your meter is completely dead it looks like you might be able to re-use the printed metal label plate in another meter if the replacement meter is similar in dimension.

[2600]

This trick usually works well. Not always, but usually.

I blame it on the polystyrene plastic housing. That stuff tends to shrink with age. Maybe that's what causes the pivot tension to increase.

I prefer to spread a sheet of white paper on the work surface. Even the tiniest stray particle of steel shavings will stick to the meter's magnet. If it gets into the gap between the magnet and coil, it will jam.

Any stray particles on the work surface will be more visible against a clean white background.

Loosening the lock nut on the tension screw will make the tips on your jeweler's screwdrivers last longer. Turning that screw with the locknut still tight is hard on them.

Good chance that the S-meter on that radio will need the same thing before too long.

73

[Sandbagger]

Sept 4, 2013 9:13:26 GMT -5 BBB said:

When I got a Cobra 2000 a few years ago the Modulation/ SWR meter was stuck in the middle. I figured the meter's movement coil was still good as the meter would try to move once and a while.

I decided if it was bad and needed replaced I would pull it out and dissect it to see what failed. I have heard that there is a bearing pre-load adjustment on some meters. Sure enough, I backed out the super tiny front brass screw just enough to free up the meter movement. Now it's back in action.

If you back out the screw too much as I did at first haha, the horizontal movement axle pin will pop out of the brass bearing. Don't worry as you can carefully guide it back into the bearing. The needle return spring is very fragile so take your time re-inserting the pin.

To remove the meter, there is a sheet metal retainer behind that has two screws in it. I was able to use a long Phillips screwdriver to get at them. Un-solder the meter leads and remove the meter. The front clear plastic cover is simply scotch taped to the back of the meter from the factory. Then you can get at the front bearing screw. There is a bearing screw on the rear as well but I have not had luck adjusting this screw on meters for some reason. There is also a meter needle centering fork adjustment on the rear of the meter accessible thru a slot if you need to set the meter at zero.

If your meter is completely dead it looks like you might be able to re-use the printed metal label plate in another meter if the replacement meter is similar in dimension.

A lot of meters will become "sticky" after many years of use. This can happen due to a "spot" being worn into the bearing. I've found that simply turning the screw at the front (or back) of the meter movement 1/4 to 1/2 of a turn out will force it to use a different part of the bearing, and usually will free the movement up again. Of course, this may be only last a short time, like so many other quick and dirty repairs, so you take your chances. And yes, there are a number of meters out there which share the movements and other "guts". I've transplanted movements and meter cards from one meter to another and managed to restore functionality. All the more reason to have dead carcass parts radios around....