And the "Dumbass award of the year" goes to:

[Deleted]

Me! I put a Cobral 1000GTL on the bench that I was told had a receive problem. When I fired it up, it had loud electrical noise that was coming over the receive. After playing with it, I finally figured it out. Some switches named NB and ANL were turned off!



Receive is really poor, though.

[Tombstone (R.I.P.)]

Ha, ha, ha. Try aligning the receive and see if it gets better.

Tombstone

[Deleted]

Just did. Sounds better, but not great. My TRC-455 and RCA Co-Pilot blow it away on recieve. It appears to be hacked.

[Sandbagger]

Nov 20, 2008 21:18:10 GMT -5 @vinnies said:

Just did. Sounds better, but not great. My TRC-455 and RCA Co-Pilot blow it away on recieve. It appears to be hacked.

Then you have your work cut out for you. Correcting misbehaving radios is nothing compared to undoing a mad-scientist's experiment gone horribly wrong.....

[Deleted]

This one will be quick. I am giving it back. There is a mod underneath where 2 transistors were added, and the tone control was turned into a variable dead key. I cannot get the radio to do more than 2W, with 5W swing. I am really going to put a stop to taking radios, especially in his condition. The S/RF meter seems jumpy and sticky. When I calibrated it, it was erratic. I do not know if this is the meter or what.

I aligned the receive to the best of my ability, and I am giving it back.

[Sandbagger]

Nov 20, 2008 23:05:29 GMT -5 @vinnies said:

This one will be quick. I am giving it back. There is a mod underneath where 2 transistors were added, and the tone control was turned into a variable dead key. I cannot get the radio to do more than 2W, with 5W swing. I am really going to put a stop to taking radios, especially in his condition. The S/RF meter seems jumpy and sticky. When I calibrated it, it was erratic. I do not know if this is the meter or what.

I aligned the receive to the best of my ability, and I am giving it back.

Interesting that the receive is low, and the transmit is low as well. This suggests a common cause, like perhaps something in the final filter section before the antenna jack is out of whack. Also check diodes D1,2 and D3. If any of them short, it will pull down the receiver and may pull some of the transmit power down as well. Also make sure that the voltages are correct.

That is, if you haven't given up already...... ;D

[Tombstone (R.I.P.)]

I hate hacked radios, I don't know how many jumpers across power resistors that I've removed. Sensible mods that don't strain the radio or put nasty holes and switches in the are one thing but I've seen some real butcher jobs. Repairing radios can sometimes be challenging enough but as Sandbagger says, figuring out what's been done and why with a hacked radio is really tough.

Tombstone

[Deleted]

Dave, If the meter is sticky and not linear, is that the meter that is bad? There is a cap in line with that. The guy wants me to replace all the caps, which number 34. Only $3.66 for mouser plus shipping.

[Sandbagger]

Nov 21, 2008 22:45:30 GMT -5 @vinnies said:

Dave, If the meter is sticky and not linear, is that the meter that is bad? There is a cap in line with that. The guy wants me to replace all the caps, which number 34. Only $3.66 for mouser plus shipping.

The meters on the Cobra 1000/2000 are notorious for getting sticky. It's a problem with the movement's bearings, and if you're are REAL careful, and good at micro-surgury, you can often correct it, at least temporarily. Most people choose to replace them, but replacements are getting harder to come by.

[Deleted]

Can I lube it with WD-40 or such? I usually use a syringe with a dull needle to do precise lubing.

[2600]

If you look at the rear of the meter, the screw that sets the tension on the pivot bearing is visible through a hole that's covered by clear tape.

A quarter or half turn of this screw counterclockwise will often free it up.

Tricky part is to soften the dab of enamel they use to lock the screw in place. If they didn't use much on that one, a jeweler's screwdriver may turn it. And if it's locked down, you'll twist the blade on the tool trying to turn it.

73

[Deleted]

Will do. I had gotten to that point of removing the tape, and did not go any further until I heard from here. should I lube it from the front in any way?

[Tombstone (R.I.P.)]

No, don't lube it, just back the screw off counterclockwise a little like 2600 says, You can soften the enamel that they used to lock the screw by lightly heating it with a soldering iron so as not to melt the plastic.

Tombstone

[Deleted]

Did loosen it. Will try and then update here.

[Sandbagger]

Nov 23, 2008 9:37:48 GMT -5 @vinnies said:

Did loosen it. Will try and then update here.

Be VERY careful when loosening the bearing screw. If you loosen it too far the meter movement needle will fall out of the bearing and it will not work and getting it back in is a little tricky, especially for those of us who are losing the ability to focus on small close objects . Only a slight crack of the screw is usually necessary to free up a sticky movement. I would not go more than 1/4 turn.

[mark4]

I worked for a meter manf for 16 years.
DO NOT OIL THE METERS!
These are what is known as a pivot and jewel meter.
But these are very cheaply made.
Sometimes loosening the jewel adjust slightly MAY help.
Other times this is due to years of the glass jewel wearing from the pivot turning in it. Fine particles of glass in the base cone of the jewel causing the meter to stick. We built the BIRD watt meters. And don't blow the meter out with a air hose you will destroy the hair spring. If there was anyway of saving that meter the chance will be gone. Barkett has in stock Brand New Cobra 2000 meters for sale. And as for another Dumb Ass award. stupid stickers on e-bay to put on the face of your Cobra 2000.

[Deleted]

OK, update. The screw turn in the meter, did the trick. Also, I recapped the radio. A few of them must have been bad, because the receive was dramatically improved. I noticed some of the caps were underrated on voltage, like 6 or 10 volts, so all the caps I replaced them with were 25 volts. Seems to work like a charm now.

[Sandbagger]

Nov 28, 2008 23:26:42 GMT -5 @vinnies said:

OK, update. The screw turn in the meter, did the trick. Also, I recapped the radio. A few of them must have been bad, because the receive was dramatically improved. I noticed some of the caps were underrated on voltage, like 6 or 10 volts, so all the caps I replaced them with were 25 volts. Seems to work like a charm now.

Those 10V caps were notorious fail-prone devices in the Cobra 2000, so it stands to reason that they would fail in the 1000 as well. Good job!

[Deleted]

Thanks to all. I let the guy know that I get most my answers from this forum.

[Deleted]

BTW, I went over the receive 3 times, and seems excellent. Just one thing. This radio seems to have a higher level of white noise or hiss, when there is no signal coming in. Seems much higher than my TRC-455, which almost has no noise. Is there anything that can be done about this?

[Sandbagger]

Dec 3, 2008 13:49:50 GMT -5 @vinnies said:

BTW, I went over the receive 3 times, and seems excellent. Just one thing. This radio seems to have a higher level of white noise or hiss, when there is no signal coming in. Seems much higher than my TRC-455, which almost has no noise. Is there anything that can be done about this?

Maybe. I've noticed that there are some radios that are just noisier than others. My TRC-451 has one of the quietest noise floors, while my Royce 640 has a fairly noisy one. Some of that may be how the AGC is set up, some of it may be inherent in the design and the choice of RF front end parts. A receiver's noise figure is set in the first RF stage. A good low noise device can be a big help in keeping the "white" noice level low. There are some mods floating around that claim improved receiver performance by replacing the stock bipolar RF part, with a different part such as a 2SC2999. I haven't done any of these, although I'd like to try just to see what I find.......