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Peel 'N Stick variable key for the Cobra 29 radios. No joke.

Discussion in 'CB Radio Modifications' started by nomadradio, Mar 20, 2019.

  1. nomadradio

    nomadradio Analog Retentive

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    Here's the first attempt at a "How2" install a gadget we call the "Peel'N Stick Variable Key".


    It's configured for easy installation. Like most of our odd widgets it came about to save labor here performing a popular mod.

    [​IMG]

    It's designed to fit neatly in the Cobra29 type radios, but works in most any AM-only CB. It has two bare wires coming out the bottom. They go into the two holes left by removing the jumper wire that feeds the radio's driver transistor. It's usually marked "JP36".

    [​IMG]

    A ground wire coming out of the top edge of the board goes into a hole in the radio's circuit board at the rear corner.

    [​IMG]

    You may have to scrape mask paint to expose the ground foil, or simply strip enough from the ground wire to reach and lap-solder to a solder point on the board.

    [​IMG]

    The three wires that go to the front-panel control are marked "CW" for clockwise, "Wiper" for the center lug and "CCW" for the minimum end of the control. It's probably easiest to simply unhook the wires from the radio's SWR Cal control and use it as your carrier control. The PNSVK is built to match the 5k pot used for the SWR Cal. Other value pots will work. I'll probably just pack a 5k control that fits the front panel of the 29 radios with the board. You can mount it where you want, or replace the factory control if someone has already roached the pot's resistance element with a bogus hookup in the past.

    [​IMG]

    The heat sink surface should be prepared first, by swabbing it with rubbing alcohol or your favorite non-residue solvent. This insures a good bond with the double-sided foam's adhesive.

    [​IMG]

    The double-sided foam tape we use is a commercial product made by 3M called "VHB". The guy we got it from said it was used to attach serial number plates to diesel engines. We have found that heat strengthens the bond. The drug-store double-stick foam tape tends to harden and come loose when exposed to heat. This stuff doesn't.

    [​IMG]

    Once the bare wires are inserted into the holes where JP36 was removed, line it up first before pressing it against the heat sink. Once it has adhered, it won't want to come loose. I recommend a good squeeze with needle-nose pliers just to be sure of a good bond.

    [​IMG]

    Lordy, it's past my bed time. I'm gonna post this and just come back later to proofread and see that I didn't scramble the order of the images.



    This kit isn't ready for prime time just yet. The first samples are going out to folks who will be the "guinea pigs" to see if we screwed anything up with this first production batch.

    Oh, that trimpot on the board serves to set the minium carrier power. Just seeemed worth the extra bit of trouble to have that.

    More later.

    73
     
    LeapFrog, Redbeard U812, NZ8N and 6 others like this.

  2. sonoma

    sonoma Sr. Member

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    nice setup Nomad. are you selling them?
     
  3. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Very nice!
     
  4. Low_Boy

    Low_Boy Well-Known Member

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    Very nice
     
  5. Mk121

    Mk121 Active Member

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    Awesome job making that widget! Very nice and tidy. Any idea on how much you would be selling it for?
     
  6. Old_Crow

    Old_Crow Active Member

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    Great idea!
     
  7. nomadradio

    nomadradio Analog Retentive

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    Once I know that the setup I ship to the guinea pig users looks good, then comes the hard part. Packaging and pricing. That will include a 5k panel control already wired up.

    Should come in under 35 bucks. Yeah, it's more than the "rabbit turd with wires" versions. Hopefully the labor it saves will justify the sale price. This setup is meant to hold up for customers driving dump trucks. The loose rabbit-turd-with-wires always seemed a bad bet in radios that get hard use. This is probably overkill for 9 out of 10 users, but so be it.

    Thanks for the kind words and 73
     
  8. Eldorado828

    Eldorado828 From the high plains of Texas

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    Nicer work Nomad, I'm in line when they become available!
     
  9. PA770

    PA770 W9WDX Member

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    I'll be in line.. my old C29 from 95 would be nice to have for my various amps..
     
  10. Shockwave

    Shockwave Sr. Member

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    That should help clean up some of the messy installations. If you can solder a mic plug on, you can install that variable too.
     
    Shadetree Mechanic likes this.
  11. 543_Dallas

    543_Dallas Sr. Member

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    I still prefer to mount the transistor to the hestsink with a screw. Since the tab on the transistor is connected to b+ I don't want it flopping around in there.

    I suspect a few people will just wrap the thing in electrical tape and toss it in the radio anyway.
     
  12. Big Kahuna

    Big Kahuna Well-Known Member

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    Nomad - when you are ready to launch let me know and we can put up an article on the CBRadioMagazine website and I'll work with you to produce a video for YouTube.

    I'm sure that will help get kick-off your sales push.

    I love to promote this type of stuff, especially when it comes from a forum member.
     
  13. Cutlass327

    Cutlass327 Active Member

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    If it will work in a Cobra 25WXNWST, I'll go for one. Will have to mount the pot in the lower cover, but I don't care. It will just add to the echo knob that will be there too.
     
    Shadetree Mechanic likes this.
  14. nomadradio

    nomadradio Analog Retentive

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    Hey Big Kahuna, thanks for the offer. Building the boards is just the start. Need to get them wired up to a control and packaged to ship.

    Need another case of "round tuits".

    It works in the Cobra 25 just fine.

    73
     
  15. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Any updates?
     

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