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Cobra 29 from 1995.. see any mods?

Discussion in 'CB Radio Modifications' started by PA770, Nov 4, 2018.

  1. PA770

    PA770 W9WDX Member

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    Here the insides of my new to me 29..



    Anyone see any mods?? This thing seems to have good ears on it too..

    IMG_20181104_171224885_LL.jpg IMG_20181104_171242593_LL.jpg IMG_20181104_171248610_LL.jpg IMG_20181104_171328886_LL.jpg IMG_20181104_171413386_LL.jpg
     

  2. sp5it

    sp5it Master of puppets

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    Keep it stock. Best choice IMO.
    Mike
     
    jon666 and Captain Kilowatt like this.
  3. PA770

    PA770 W9WDX Member

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    Planned on it. I don't see anything done to it.

    But I am not a tech either..
     
  4. sonoma

    sonoma Sr. Member

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    I can not find D11 in place. the location is covered by wires. is by the large transformer towards the front of the radio. about 1 inch
     
  5. PA770

    PA770 W9WDX Member

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    Left side or right?? Again I am not a tech
     
  6. PA770

    PA770 W9WDX Member

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    Found D11.. someone cut one leg.

    IMG_20181104_192442128.jpg
     
  7. kopcicle

    kopcicle Sr. Member

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    If used ahead of an amplifier see Nomadradio about a "lick and stick" power adjust.
    I'd reinstall the limiter.
     
    Robb likes this.
  8. PA770

    PA770 W9WDX Member

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    That's the plan, to reinstall it in a few weeks as I am broke from buying this 29 and the 148 GTL..

    Will be sending to local guy in Carlisle PA.

    Currently dk is like 2w and swings up from there..
     
  9. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Most of the time the reason why it works as well as it does, even receiver wise, is because they don't spend a lot of time in there ---

    Typical Clip n' Run
    D11.jpg
    Aside from that I wanted to point out something else too - that many newer boards don't use...
    D11Plus.jpg

    It's nice to see "The real thing" come across my desk very now and then. This one is legit but it has had some changes done to it.

    The "genuine article" from those years used a jumper along with JP36 - this still has both.

    D2 and D1 - part of the front end, and perhaps the reason why your receive is good, is one of those is the genuine article of 4148 diodes used in these board. They worked in this section - just can't tell why unless I can locate D3 part of the RF gain lead trace going back there - C11 was part of this too.

    Sorry about the D11 thing. But for that you have and how it performs - D11 is a moot point - you can fix that. But it no longer is pristine OEM - just OEM - they kept the diode in there.
     
  10. sonoma

    sonoma Sr. Member

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    the top of the board looks fairly clean. D11 is the way most do it to get more audio out. back when I worked on radios that was the most common item that was clipped just to make the radio swing. I always liked the JP36 mod myself to get more audio out of the radio.
    just my opinion.
     
  11. sunbulls

    sunbulls Well-Known Member

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    It looks like someone turned the VR 1 pot all the way up (max). VR 1 calibrates the S meter reading during receive. If you think your radio is receiving great, directly compare it to other radios until it can be adjusted with proper equipment. You’re merely being deceived by looking at a misadjusted meter. Meter trickery, especially deliberately misadjusted watt meters is common among dishonest techs.
     
  12. PA770

    PA770 W9WDX Member

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    Actually with RF gain knob below noon I hear almost nothing and the meter is zilched. I run about 2 oclock and get just below 1s unit of static floor.

    What I meant was distant stations seem to come in great and clear over my other radios ability to RX then without a ton of static hiding the signal.

    When I get like $50 I'll be sending it out for repair and proper tune. It's $25 for tune and shipping.. hence $50
     
  13. kopcicle

    kopcicle Sr. Member

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    Part of what us cantankerous old farts here do is attempt to convince you to do the work yourself. With an am radio frequency isn't that critical and replacing/repairing the diode is entry level shiznit. Consider it anyway
     
  14. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    It's ok - you don't need to explain the cost, we're trying to help you...

    Found other things that in comparison - some call these revisions, others call it a "Cheapening"

    Here's a "montage" of some of the older board, that I used to work on, that I miss...
    R28VR1OLD.jpg
    Upper corner photo? With the hole? Is where the 52MHz trap goes - some other parts appear to be reworked as revisions that are "modern" which I am suprized to see for that era - e.g. - why upgrade when they could keep it like the older style. (Meaning manufactured later in time?) Another - the rework of the SWR section (R5C83) - but in this case - it looks like they took an older board and just repopulated it - like a refurbished board would be (Canada import type of thing) only revised with newer parts.

    You mentioned the receive of the radio - well, look at the position of VR 2 - Mid-point - this controls more IF than receiver - and it's like, not "set" or even messed with. Like direct - from the original factory off the assembly line tune and check. The only other reason why I posted that pic is because of the R28 location - anyone whom has used these boards for oddballs, needed R28 as a swamp resistor to broaden the IF curve for receiver performance OOB. (Pirate radio)

    The other two clips of the yellow IF can, is for the RF gain control - your radio still uses the typical 1N4148 - but for one of them to be swapped with a different case assembly design versus the "black band - saturated color" design - tells me something - like perhaps it's a Schottky diode inserted to help with performance for VR1s' sake.

    Why the above, well - here's the newer version boards...
    Cobra29LXLEVR1.jpg
    This one is that same VR1 location - expanded to include more of the IF strip - the R28 is missing in later revisions. Sigh - you just have to remember where to place the R28 and even if the IF can, can take the mod.

    Another section...
    D11PlusLXLE.jpg
    This one is the RF Gain section - D3 typical 1N4148 and D11 is intact - note the "saturated colors" these two diodes have - that's what I'm talking about. Different manufacturing origin.

    So this radio "survived" - at least the dating of the parts are from that era in time - the PLL 958 number tells me 95 is a good bet and the pre-driver is an older silkscreened C941 - meaning it's stock more than not - so it really is a keeper - they may have done work to upgrade it as a refurbished - but that places the radio in a questionable category when it comes to the Electrolytic caps failing prematurely.

    Here's is another example of the JP36 and a second jumper on the other side - now revised to a simple cap reoriented and routed differently...
    CobraLXLED11PLUS.jpg

    To me this is a good radio to own - for it' has the older board that you can work with soldering wise as well as durability - better than the newer ones.

    I'd be happy with it - someone took the time to go thru it but left it stock as much as possible - which would be a credit to you for that - the only place I see any wear and tear is off on the "white core" IF can showing some re-tweaking - more from the secondary alignment than the factory one. Hence the VR1 hard over issue. They didn't know how to tune in tandem with VR2.

    The less it's messed with the better off the new owner is...
     
    #14 Handy Andy, Nov 5, 2018
    Last edited: Nov 5, 2018
    PA770 likes this.
  15. kopcicle

    kopcicle Sr. Member

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    remind me to take pics of my 29 :) . It' "modified" heh
     

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