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Cobra 29 LTD classic tune up

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  #1  
Old 12-09-2008, 03:33 PM
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Default Cobra 29 LTD classic tune up


Ok I know how to do the mosfet mods but had a question about the basic tune up. How do you do just the basic tune up without the mosfet mod? the reason I ask is when my uncle gave me his radio I took the radio into a local CB shop and had a tune up done to it I witness most of it but from a distance I saw them desolder a resolder some componets most look like the blue electrolytic caps and a few other thing I know they tuned the coils and removed the L14 slug after all said and done it boosted my watts to about 25 on there meter and the same when I checked it on my meter. I have 2 Cobra 29s now the original one my uncle gave me its been tuned (by a cb tech) had the mosfet done by me and the schotty recevie mod also done by me and retuned all the coils for max watts which this radio has about 40-45 watts on my meter. My other radio all thats been done to that one is the mosfet mod and the schotty recevie mod and only put out about 25 watts but it hasn't had a tune up yet i would like to do it myself but need the info on it I really don't want to take it in and have it done and have to drop another $40 on the tune up for this radio so anyones help would be awesome thanks for reading this if it dosen't make sense just let me know and I'll explain it better


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Old 12-09-2008, 11:47 PM
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Not having done the Mosfet mods on a cobra 29, and not knowing what the tech did on the one radio, it's difficult to say without seeing the radios. For the mosfet mod, did you follow the instructions on cbtricks:
http://www.cbtricks.com/miscellaneou...bra_29_mod.jpg

Also, I don't really agree with removing the tuning slug on L14. The thing to do is remove one of the turns on the coil if it has 5 turns. Most (if not all) the newer 29's have five turns around the coil, but it only needs four. If you take one turn off, you can get better output by tuning the slug instead of just removing it. NOBODY seems to know that you can do it this way, so I just gave you a worthwhile tip there

I prefer to do the 50 watt mod using the 2SC1969 final method, but I realize that those transistors are going to get difficult to find soon. If you want, I can give you the details on how to do it that way. This method will yield about 45-50 peak watts and 10-12 avg watts. You could probably do all the same steps for this mod and incorporate the MOSFet mods for some really good results, but I haven't tried this yet. Maybe I'll have to pick up a 29 to try it with

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Old 12-10-2008, 10:27 AM
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Yeah that's the mod I did

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Old 08-29-2009, 07:25 PM
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Default 50 watt mod

Quote:
Originally Posted by moleculo View Post
Not having done the Mosfet mods on a cobra 29, and not knowing what the tech did on the one radio, it's difficult to say without seeing the radios. For the mosfet mod, did you follow the instructions on cbtricks:
http://www.cbtricks.com/miscellaneou...bra_29_mod.jpg

Also, I don't really agree with removing the tuning slug on L14. The thing to do is remove one of the turns on the coil if it has 5 turns. Most (if not all) the newer 29's have five turns around the coil, but it only needs four. If you take one turn off, you can get better output by tuning the slug instead of just removing it. NOBODY seems to know that you can do it this way, so I just gave you a worthwhile tip there

I prefer to do the 50 watt mod using the 2SC1969 final method, but I realize that those transistors are going to get difficult to find soon. If you want, I can give you the details on how to do it that way. This method will yield about 45-50 peak watts and 10-12 avg watts. You could probably do all the same steps for this mod and incorporate the MOSFet mods for some really good results, but I haven't tried this yet. Maybe I'll have to pick up a 29 to try it with
Please email me with the 50 watt mod using the 2sc1969 transistor thanks. cbwizz2003@yahoo.com

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Old 08-30-2009, 12:49 AM
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Post it on forum. I'm also curious how to get 40W from 16W transistor
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Old 08-30-2009, 06:19 AM
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Old 08-30-2009, 03:05 PM
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it has been discussed many times here on the forum.

the reason the 1969 will do 40-50 watts PEP in an AM "transformer modulated" chassis is because when you modulate, the transformer steps up the voltage to the final and driver way past 13.8 volts.

dont just take my word for it, do a search here on the forum, and you will come across at least a couple of threads dealing with this phenomenon.

oh, and here is the mod for anyone thats looking for it:
http://www.worldwidedx.com/radio-rad...ransistor.html

LC
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