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got an ole cobra 139 base.

southerntrucker

southerntrucker

rebel child
Jan 29, 2012
80
5
18
30
texas, the good ole south
Hey guys.. I had an ole cobra 139xlr base givin to me the other day. Everything seems to be ok but I can't get it to key up. It keys up but I look on my external meter and it don't show to be doing anything. It just bearly moves. My mod meter moves on the radio so I kno its got modulation but the power meter don't move when I key up. Can somebody help me please? Thanks.
 

If you are seeing 1/2 to 1/4 of a watt output total on a meter; then it may need to have the final transistor (a '2SC1307' I believe - hard to get but might be replaced with a 2SC1969 - not sure about that) replaced. If you aren't seeing ANY power; then it may be beyond a beginner to fix - IMO.

http://www.cbtricks.com/radios/cobra/139/graphics/cobra_139_sch.jpg

Remember, that you MUST have an antenna (or a 50 ohm 'dummy load') hooked up to the radio output FIRST when testing or using ANY radio in transmit mode ! ! !

If replacing the final output transistor, you will need to re-adjust the bias current for both the driver and final transistor. That is; if you want to do it right - IMO.

Still - all in all - not a bad deal for 23 channel radio.
But I would definitely consider getting a 40 channel radio instead - IMO . . .
 
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First off, remove the case and spray all of the switches and controls... and especially the channel selector... with a good dose of electrical contact cleaner. You can buy a large aerosol can for about 10 bucks at Radio Shack. If you're buying old CBs that haven't been fired up in years, the cleaner will pay for itself many times over. 90% of all problems with old CBs that have sat in storage for years are caused by dirty contacts... especially the channel selector mechanism.
 
Thanks guys. And the radio is a 40 channel. I ain't had a 23 channel in years lol. And yes I am do have the meter on 20 watt setting. Then I change it to cal to calibrate my swrs and the radio dont even have enough dead key to calibrate them. And I'm usinng an imax 2000 ground plane to do all this with. You also said that it might be the finals. I was thinking that as well considering I had a mobile cobra do the same thing. But I'm not quite sure which one it may be. I really don't have as much expierence wokin on bases like I do mibiles. And thank y'all for trying to help out a newbe. Most places don't do that much anymore. Thanks again guys.

Southerntrucker
 
Sweet radio, 858 chassis, channels for miles in that chip.

Same chassis as Navaho TRC 457 or 458, one of the best SSB rigs ever made.

there is much info on the net about that rig, seems I recall a small cap in front of the relay that will go bad and cause no output as it messes up the relay function.

Hard to tell if the radio is not on my bench.

It is worth fixing and getting a good alignment on it. Talk circles around the export radios in audio quality and receive performance.
 
southerntrucker said:
Thanks guys. And the radio is a 40 channel. I ain't had a 23 channel in years lol. And yes I am do have the meter on 20 watt setting. Then I change it to cal to calibrate my swrs and the radio dont even have enough dead key to calibrate them. And I'm usinng an imax 2000 ground plane to do all this with. You also said that it might be the finals. I was thinking that as well considering I had a mobile cobra do the same thing. But I'm not quite sure which one it may be. I really don't have as much expierence wokin on bases like I do mibiles. And thank y'all for trying to help out a newbe. Most places don't do that much anymore. Thanks again guys.

Southerntrucker
Click to expand...

Oh; you meant the Cobra 139 XLR radio!
http://www.cbtricks.com/radios/cobra/139xlr/index.htm

That is definitely a horse of another color.
That uses a 858 PLL chip and chassis, an excellent radio to restore and use if there ever was one. One of the best of the oldie but goodies. Extra fine receive and transmit. It uses the 2SC1307 final transistor and it is hard to get. If you cannot fix it; it is worth it to send to a great shop like DTB Radio and have them repair it and give it a full alignment too. A real keeper!
 
I agree with Robb. I have one of these in very good condition. It never even had the clarifier done until last week while I was having it aligned. It's no 2000GTL but it isn't far behind in the running.

IMHO: Keep it and use it!
 
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Okie dokie. Dang i didn't kno I had such a good radio. Lol I thought it was just another pos base that I got givin to me. But the way eveyone talks it seems to be a lickable radio. So I guess ill sink some money into it and see if I can't get er goin. I also got my hands on a non amplified D-104 desk mic today as well. The guy didn't want it just cause it didn't have a cord on it. So I said hell no. Don't throw it away. Ill take it lol. So I got er home and put a new cord on it and it works good as new. Not very much modulation with it, but I think it will be perfect for that cobra. And onther guick question, if I was to go about fixing the cobra myself, where exactly is the final that I have to replace located? I looked everywhere and I couldn't seem to find it? Could somebody possibly give a reverence pic? Just curious. And again, thanks for all ghe help guys.

Your friend, southerntrucker
 
badfish said:
I agree with Robb. I have one of these in very good condition. It never even had the clarifier done until last week while I was having it aligned. It's no 2000GTL but it isn't far behind in the running.

IMHO: Keep it and use it!
Click to expand...

I will take that 858 chassis any day over a cobra 2000, way better transmit audio and the receive is better than any older cb out there, the 2000 does run a close second but that old 858 if aligned properly and re capped, will run circles around that 2000.

That chassis is not a power house so do not expect big wattage numbers out of it, but what you do get is pure quality.
 
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Ok. I found me a mishibishi (can't spell lol) 1969 final out of an old 29 and replaced the and replaced the 1307 one. It now keys up but I had a driver say that he could hardly here me like 2 miles away. I don't get it? Everything shows to be wor king now. And also the two 1419 finals in the back look all rusty brown where the wires are soldered to it. What should I replace them with? Thanks for all the help fellas.


Southerntrucker
 
Ok. Disregard that. Its workin ok. I got a local to help me out. But I still need help on what to replace those 1419's with.

Here is what the radio is doing now.
Keying bout 4 swinging 8 when talking and up to 12 when I whistle
Usb keying 0 swinging bout 11
Lsb keying 0 swinging bout 11

Than its also got other channes as well. At least that's what I asume thr little toggle switch oon the front is. And I'm guessing its the high and low channels? And I also have even MORE channels when I flip the anl switch. Now those I have no clue about considering I have no freq meter or counter. Also, if I am correct. My clarifier has been cut. Because when I turn my voice lock knob, it messes with both the receive and out-put freq. Or that may just be how it works. Iv never had a radio like this b4. Lol
 
Think I would be more concerned that the final bias is set correctly so that you don't end up frying the transistor you just swapped in there than be concerned about the channels. Final bias in this radio is 40mA and the driver is 15mA. Did you put a new coat of thermal paste on the replacement final when you installed it? Very important to do that - BTW.

Don't know what kind of power meter quality/brand you are using for determining the output of the radio. But in reality if it is close, then the watts on SSB are a bit low (should be like 16 watts on SSB). AM watts seem fine. Since you got it working, might be a fine time to send it to a shop for a full alignment and have a real tech to give it a close examination and a clean bill of health. But then again, that is what I would do . . .
 
Alrightly. Ummm... how exactly do you set the bias? If you don't mind me asking.. and also I found a 1306 final (which if I remeber from what I read is the driver) I an old rca mobile. Would it hurt to change that one too? Or do I just need to let it be?

Southerntrucker
 

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