Question about Cobra 25 LTD 40-Channels Base CB Radio

1 Answer

Hello, i was given a cobra 25ltd classic to look at.. put it on freek counter keys up around 24,25 mhz with the last few numbers flutering around it will not stay still. when modgulated into it goes down in frequency any help would be great.. thanks ~shredder~

Posted by on

  • 1 more comment 
  • shredder67 Nov 18, 2010

    hello, 148 still doing good i do belive its fixed.. the 25 has a pll that says cobra 25 on it no other numbers so ? thats to much work 25s are fairly cheep . and as i didnt have enough problems thic week now mt 148 is getting extra supper hot on the back right behind the final.
    key up and talk for 30 sec and its so hot you cant keep your finger on it...shorted final im thinking..just one of those weeks ugg!! thanks mchaos you have been very helpful
    ~shredder~

  • shredder67 Nov 19, 2010

    i posted some thing and it didnt show up ?wonder what the..... freq. problem fixed much thanks . i think i shorted the final when i key up the final gets so hot you cant touch the back of radio and like real quick . just key it up and it starts to get hot right away... thanks ~shredder~

  • ReKoiL Jul 17, 2012

    What happens when you turn on your cobra 25 nw ltd classic an d10 starts to smoke? Why is this happening?

×

Ad

1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

    Guru:

    An expert who has written 7 tips or uploaded 3 video tips

  • Master
  • 773 Answers

Does it seem to be talking on the right channel??

Check to see if D10, which is supposed to be an N1004 diode, and see if it's been replaced with a jumper.

If that's the case, then the final is volted. This mod gains some wattage but can make a radio dirty. Putting an N1004 back in may fix the issue.

However...

Usually the radio will deadkey on the right freq.

The VCO could be off, and the radio may need to be aligned. Could the person you got the radio from have randomly turned VR's in the radio trying to mod it?

Without an ocilliscope you cannpt fully align the radio, but if you have a volt meter and a watt meter, you can do some of the alignment.

here is an alignment guide.

But if you can hear people on the correct channel, and they can hear you fine, it could be just a volted final.

Posted on Nov 09, 2010

  • 3 more comments 
  • shredder67 Nov 10, 2010

    hello, the radio is not right. cant hear anyone nor can they hear me.keys up around 24,25 mhz and when i talk into it it goes down to around 17 - 13 mhz. no volted final. i think the guy got it at a truck stop and just put it in stock. nothing looks to be tinkered with. the guy handed it to me and said it just quit working.it works just not on 11 meters, so i'll try tweeking the vco a little.i also have a 148 that goes up in freq. around 28.000.00 and then a few hours later it will act normal then back to wacky. thanks a lot

  • Don Reiman Nov 10, 2010

    It could just be a bad mixer crystal in both of them. Most defiantly what's wrong with the 148. Take a soldering iron, and heat the mixer crystal up for about 2-4 seconds. Some times this resets it.

  • shredder67 Nov 15, 2010

    thanks, ill try that

  • shredder67 Nov 16, 2010

    hello, well i changed the 11.325 crystal and so far so good. guess i'll see how it goes for a few days.....thanks mchaos now on to the 25 still workin on that.. but one down one to go, thanks again...

  • Don Reiman Nov 16, 2010

    Well the 25 could have a bad PLL chip. In which case, if it is, then unless you own an oscilloscope it's almost not worth fixing.

    When you replace a PLL chip, the entire radio needs to be re-aligned with the manufacturers alignment procedure outlined in the factory service manual. www.cbtricks.com has a large database of service manuals. They have the one for the cobra 25.

    In order to completely align a radio you need a watt meter, volt meter and oscilloscope. You can give it a shot skipping the procedures using the oscilloscope, but most likely the radio will bot be properly aligned.

    Here is what I would do to make sure the VCO is locked in correctly on the cobra 25.

    Using a volt meter in DC mode. Ground the black lead. Connect the Read lead to the junction point of R59 and R60. Adjust L15 (vco) to obtain a voltage of about 3.5, plus or minus .2 volts. Basically as close as you can to 3.5 volts. Then the VCO will be aligned. Further alignment for the TX requires an oscilloscope.

    Good luck.

×

Ad

1 Suggested Answer

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi,
a 6ya expert can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of.(from cars to computers, handyman, and even drones)
click here to download the app (for users in the US for now) and get all the help you need.
Goodluck!

Posted on Jan 02, 2017

Ad

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

Working on a 25ltd classic that was wired backwards and wouldn't power up. I changed diode and it lives again. 10 watts output no modulation.


10 watts is illegal. Modulation circuits didn't fare so well. A lot of components fry when you reverse polarity.

Dec 31, 2015 | Cobra 25LTD "Classic" CB Radio

1 Answer

How to increase the receive on a cobra 25ltd classic


1,if your antenna is not properly tuned you may be loosing receive as well as power 2,how your swr? 3 you may want to purchase a little driver with a built in receive amp.

Feb 01, 2015 | Cobra 25 LTD 40-Channels Base CB Radio

1 Answer

I have a cobra 25ltd my dad gave me and just had it put in my husbands truck but i cant pick up anything. Was told it could be the antenna well $30 later still not getting anything, HELP someone


a couple of problems could be causing the problem 1. make sure squalch is turned all the way counter clockwise and the r-f gain turned fully clockwise. 2 could be a broken wire at the mike plug as these get a lot of abuse all the time and if the wire going to pin 3 breake the radio will not hve any receive . hope this helped.

Feb 21, 2013 | Cobra 25LTD

1 Answer

Its a cobra 25ltd when i key the mike sometimes it hangs keyed up and does it with defferent mikes so the mike is not my problem.


take some electrical spray cleaner and lightly spray the inside of the radio where the mic plugs in. could also be a keying diode.

Jan 04, 2013 | Cobra 25 LTD 40-channel Classic CB Radio...

1 Answer

Cobra 25 that doesn't have any receive


COBRA 25LTD CLASSIC OLD MODEL TRASMIT GOOD MOD GOOD HAS NO RECIEVE

Jun 16, 2012 | Cobra 25 LTD 40-Channels Base CB Radio

1 Answer

Schematics chart


Let me give you the real deal !!!http://www.cbtricks.com/radios/cobra/25ltd/graphics/cobra_25ltd_sch.pdf

Apr 12, 2009 | Cobra 25 LTD 40-Channels Base CB Radio

1 Answer

Cobra 25LTD Classic internal neg. wire burnt when I hooked up.


COBRA RADIOS HAVE A DIODE THAT WILL BLOW IF HOOKED UP BACKWARDS, THIS IS A BLACK DIODE WITH A SILVER RING ON ONE END OF IT, YOU MAY HAVE TO TAKE IT TO A CB REPAIR SHOP AND HAVE IT REPLACED, HOPEFULLY YOU DID NOT USE OVER A 5 AMP FUSE

Apr 01, 2009 | Cobra 25 LTD 40-Channels Base CB Radio

1 Answer

Cobra 25LTD classic


that is called feed back turn down your mic gain and it will stop squelling when close to others.

Sep 27, 2008 | Cobra 29 LTD CB Radio

Not finding what you are looking for?
Cobra 25 LTD 40-Channels Base CB Radio Logo

180 people viewed this question

Ask a Question

Usually answered in minutes!

Top Cobra Radio Communications Experts

AnyMHz.com
AnyMHz.com

Level 2 Expert

500 Answers

Brad Brown

Level 3 Expert

16037 Answers

yadayada
yadayada

Level 3 Expert

76682 Answers

Are you a Cobra Radio Communication Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...