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Cobra 1000 dead, then alive, now dead

dozerman

dozerman

hello, its me again
Dec 16, 2013
186
36
38
milan tennessee
Bought a cobra 1000 today. Had been sitting for who knows how long in an outdoor building. When I got it home and took the covers off, about a pound of dead cockroaches feel out, smh. Anyway, at first it powered up. Meters were stuck, meter lights burnt as well as the receive light. Had great audio and decent wattage. Ok, replaced those items and powered back up and the alarm started going off and the diode beside the audio transformer popped. Between the 220uf cap and transformer. Nothing powers up but the clock. Switch to 13.8 plug and have everything working but the clock. Not real sure where to start. My Madison did the same thing two weeks ago
 

replace all the electrolytic capacitors and then start trying to repair them.

no point in looking for problems before eliminating the most obvious one.
LC
 
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loosecannon said:
replace all the electrolytic capacitors and then start trying to repair them.

no point in looking for problems before eliminating the most obvious one.
LC
Click to expand...
Wellllllll, I did that in my Dwight D and that's when I had to start using the 13.8 plug in the back. I'm glad you said that tho, I actually started to do that and replaced the 220uf then for some reason I plugged it back up and had nothing. No power at all on the board. And it popped the fuse in the back. Polarity was right on the cap as well
 
dozerman said:
Wellllllll, I did that in my Dwight D and that's when I had to start using the 13.8 plug in the back. I'm glad you said that tho, I actually started to do that and replaced the 220uf then for some reason I plugged it back up and had nothing. No power at all on the board. And it popped the fuse in the back. Polarity was right on the cap as well
Click to expand...



Ok new development. I now have power back on everything. Buuuut, the on air light is on until I key up and I've got a deadkey of 10 watts with zero modulation
 
This will help you get started down the right path; "Electrolytic capacitor kit for Cobra 1000 (PC-407AC)"

https://www.ebay.ca/itm/142009625640

s-l1600.jpg
 
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well im afraid your only choice is to go back and retrace your steps very carefully, as you are the only person who knows what all you have done up to this point.
trying to list all those things here isn't really going to work either, as we would have no idea which step was done wrong.

there is also the possibility that you didnt mess up any of the steps and you just have more things failing the longer you have the radio on.

there really isnt anything someone online can do to help you at this point since we would be troubleshooting a problem in a radio with more than one issue.

I make no judgments about your abilities, but things like this are the reasons that it's better to just send the radio to someone who knows how to restore radios.

lots of people (including me) give advice about how to do things yourself, but we know that only a few out there are actually going to be able to make the thing work.

my advice is starting to change though, as i seem to be getting a lot more radios in that have been 25% restored by the owner who created a problem along the way and is now lost.

those radios are much more time consuming than the ones people just buy and send to have restored.

good luck with it, im afraid i don't have too much advice to offer at this point.
LC
 
dozerman said:
Ok new development. I now have power back on everything. Buuuut, the on air light is on until I key up and I've got a deadkey of 10 watts with zero modulation
Click to expand...
Ok, so the unit will power up off of the builtin A/C power supply?
If so, verify that the correct DC voltage is going to the radio from the power supply section.

Popped fuse sounds like maybe a cap finally failed, or you accidentally created a solder bridge? (I've done it in the early days) Double check all of your work, go over every solder joint you've made.

I second what others have said, it is a wise choice to replace the electrolytic capacitors.

If the radio wasn't "new in the box" you will likely have to use contact cleaner (DeOxit) for the switches and potentiometers before everything works as it should, assuming the other problems have been resolved

Best of Luck
-Leap
 
LeapFrog said:
Ok, so the unit will power up off of the builtin A/C power supply?
If so, verify that the correct DC voltage is going to the radio from the power supply section.

Popped fuse sounds like maybe a cap finally failed, or you accidentally created a solder bridge? (I've done it in the early days) Double check all of your work, go over every solder joint you've made.

I second what others have said, it is a wise choice to replace the electrolytic capacitors.

If the radio wasn't "new in the box" you will likely have to use contact cleaner (DeOxit) for the switches and potentiometers before everything works as it should, assuming the other problems have been resolved

Best of Luck
-Leap
Click to expand...


Yeah I kept on with replacing the caps. Only found one I didn't have. But have more on the way. I found my modulation problem, a solder joint on the board. Still keys at 9 watts and has an outrageous swing. 27 pep. I didn't think this 2092 would do that. D92 was the culprit for the power loss. Didn't look bad until I touched it and it fell apart. I've got power at 13.84 going to the board from the internal supply. I appreciate all the help you guys have been. I hate sending things off to be restored, it takes the fun out of it for me. The shack is my fortress of solitude from the wife and kids lol. I keep a camera above me to record every thing I do so I can retrace anything I do. Will keep on re-capping and get back with an update
 
dozerman said:
Yeah I kept on with replacing the caps. Only found one I didn't have. But have more on the way. I found my modulation problem, a solder joint on the board. Still keys at 9 watts and has an outrageous swing. 27 pep. I didn't think this 2092 would do that. D92 was the culprit for the power loss. Didn't look bad until I touched it and it fell apart. I've got power at 13.84 going to the board from the internal supply. I appreciate all the help you guys have been. I hate sending things off to be restored, it takes the fun out of it for me. The shack is my fortress of solitude from the wife and kids lol. I keep a camera above me to record every thing I do so I can retrace anything I do. Will keep on re-capping and get back with an update
Click to expand...


Finished re-capping, still have a 10 watt key and 28 pep. Picked up some audio according to meters. On the internal supply I have those numbers. I also have a motor boat sound in my rx and the transmit light stays on. On the 13.8 plug in, those problems go away. Of course my numbers go down. 5 watt dk and 22 pep. That motor boat sound started when the fuse popped. Still looking the board over for bridged solder joints. I always take pictures before in case this happens. I know y'all are shaking your heads but if you don't ask questions, ya never know. Thanks again
 
motorboat sound means unregulated DC coming right off the bridge rectifier giving you about 23 volts fluctuating up and down (which is why you have the huge deadkey)

do not run the radio from that power supply anymore until you get it fixed.

disconnect its DC output from the main PC board and check the voltage regulator(s) on the power supply board.

that 23 volts might also be what blew that diode, but thats just a guess.

LC
 
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loosecannon said:
motorboat sound means unregulated DC coming right off the bridge rectifier giving you about 23 volts fluctuating up and down (which is why you have the huge deadkey)

do not run the radio from that power supply anymore until you get it fixed.

disconnect its DC output from the main PC board and check the voltage regulator(s) on the power supply board.

that 23 volts might also be what blew that diode, but thats just a guess.

LC
Click to expand...
Maybe someone cranked that power supply to the max?
 
kaos513 said:
Maybe someone cranked that power supply to the max?
Click to expand...
I've seen 'em go high like that before when a part fails, I don't think it can adjust to or above 18 volts in proper working condition, honestly a crowbar circuit would be a cool mod to prevent the over-voltage condition often observed (when the failure occurs) in this style of psu.
 
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