Tune up tips for a Cobra 29 23 channel.

[King Mudduck]

I just got this for $10.00. Works and looks good but only does around 11 watts and it will not hit 100% modulation even with a power mike. I have looked around and can not find any info on this. Can someone help me out?

 

[Switch Kit]

They really don't do alot , but they will work well and sound very good , have heard many with D-104s on them sounded very nice indeed. L7 and L8 should be power and D-24 should be the limiter ? if not , you can just solder it back together. You can pretty much do what you want , I honestly didn't see it go to much over 100% with a clip . but you can also add resistor to diode if it means that much to you. Iv'e seen about 15 watts or so from them radios , I think in some cases they are better set to run amps , if you drop the power to run a amplifier , chances are the audio will grow closer to the 100% mark your looking for without a clip . Have fun.

 

[DTB Radio]

Here are some untested ideas that I can suggest after looking over the SAMS schematic for the 29 (23ch). Change C69 from a 10uf to about a 100-220uf. This should allow more energy from the audio amp to get to the final/driver. Short R97 to allow more audio form the mic to reach the mic preamp. The SAMS manual doesn't show any AMC circuit, but if I remember correctly the radio does have one. I do not recall if it has a limit adjustment, though. The CB Tune-up Manual, Volume 1, says to clip one end of D24 for modulation, but there is no D24 in the SAMS schematic. If you can locate D24, I'd insert a resistor to bring up the level. Experiment with values to get the right level.

On a side note, those so-called Tune-Up Manuals are ok for general referrence as far as actual tune-ups, but you would be wise to ignore anything they say about cutting or removing modulation limiter parts.

 

[Switch Kit]

but you would be wise to ignore anything they say about cutting or removing modulation limiter parts.

to many radios I've been through or owned myself over the years , there wasn't a whole lot more you could do to them , when it comes to limiters ,sure you can add or change resistor values if it really seems to be that bad by someone else ear hole ,(Unless you have a shop full of goodies and parts that one would need to do more) especially ones with mic gains that don't have VRs' in them , or ones that don't have either going for them, other then that , I think it can be somewhat ticky tack and I personally don't think anything has to be perfect. This is a hobby for some and folks like to try different things , especially with 10 dollar yard sale specials. Yeap , for some tech's , certain radios are a blink of an eye to tune up , and 30 to 40 dollars in the ole pocket 5 minutes later (-: 3 to 4 turns and your done , well sure , it could be a few more. Don't mind me much DTB , IM just having fun and that's what it's all about for me, and I love those books you spoke of , but even with the books , without the proper equipment or the know how to use them , it would be fairly tough on anybody to be as perfect as one could possible be..................OH Yeah !! You ought to squeeze in where Justin left off and get yourself a tech section like he had in the Forum , couldn't hurt and IM sure it would be great for some extra business for you . Happy Holidays to you.

 

[King Mudduck]

Thanks guys. I use a D104 on it and everyone who hears it thinks im full of BS when i tell them what it is. I went down the road and had my wife talk on it so i could hear it and it really does sound good!

 

[Switch Kit]

first one I used for 4 years as a base was a Cobra 85 dynascan , I could plug in extra crystals into the exstention speaker jack for extra channels , it did about 5 to 15 watts , and the limiter or transistor had been removed. D-104 only needed to be cracked open , the radio did well and sounded very nice off a old Wilson 5/8 wave (Now what is called a Alpha V-5/8 by Maco) , I talked all over the world on that radio with only the power of the radio , Great DX and extra channels at that time surely helped my cause. I just went through a 29 like yours a few months back . it was remarkabley close to mint and had never been touched , there was no need to clip anything other then to bring the power down for his amp , pretty much had brought the audio up enough for it to sound very nice with that full audio sound. I truly have a passion for older radios , not so much crystal controled but right around 1976 and on .