1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice
Dismiss Notice
This forum does not allow a single user to have more than one username. If anyone wants to change their username contact an admin and it will be done. Multiple accounts belonging to the same member will be deleted without warning.

Kraco kcb4007 (what I learned before I let the smoke out)

Discussion in 'CB Radio Modifications' started by Uncle Ronnie 336, Feb 28, 2021.

  1. sunbulls

    sunbulls Sr. Member

    Joined:
    Apr 25, 2017
    Messages:
    805
    Likes Received:
    1,403
    It makes me wonder what dealer sold those Jeepers that radio, either ignorant or unscrupulous. Take your pick. I love refurbishing or improving older radios that few people want, it’s kinda my thang, but I draw the line when even SAM’S catapulted over that radio like a plague infected rat. It’s one of the very few radios that I toss into the parts bin before cracking open the covers. Once was enough. The value for me mainly consists of the LED display and the Pll.


     

  2. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

    Joined:
    Oct 23, 2017
    Messages:
    4,206
    Likes Received:
    6,232
    The AMC release cap really opens up a Cobra 29. I suspect the Kraco has a modulation transformer? You should post some pictures so we can see what you are having fun with.
     
  3. Handy Andy

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

    Joined:
    Apr 23, 2018
    Messages:
    4,536
    Likes Received:
    5,563
    +1

    Hint it does, but the parts driving it - OMG! UGH! - remember the TDA 2003? I think this one has it - much like the Mayday. I had...
     

    Attached Files:

    Shadetree Mechanic likes this.
  4. Uncle Ronnie 336

    Uncle Ronnie 336 Active Member

    Joined:
    Apr 28, 2020
    Messages:
    73
    Likes Received:
    27
    It does have a TDA 2003. Is that schematic the same radio in question? I know there was a resistor on the driver transistor which went from base to collector like it was biased in class A or something. I know I don't have this thing fully tuned out yet with the irf510 driver pushing a irf520 but even so I already got higher peaks and the audio on transmit is much louder than it was.
     
    Shadetree Mechanic likes this.
  5. Uncle Ronnie 336

    Uncle Ronnie 336 Active Member

    Joined:
    Apr 28, 2020
    Messages:
    73
    Likes Received:
    27
    Also to get close to where I'm at with the mos RF section, I basically pulled all of the air wound coils and replaced them with tuning slugs out of some parts pigs. I put the smoke back in and we are back in business as far as getting this thing maximized. I have another question about the modulator, is the TDA 2030 a drop-in replacement?
     
    Shadetree Mechanic likes this.
  6. Handy Andy

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

    Joined:
    Apr 23, 2018
    Messages:
    4,536
    Likes Received:
    5,563
    Need the "clipping Drive" diodes to help clamp the spikes so they don't blow the output Change C36 Electrolytic to a 150ohm 1/2W resistor, install a 4.7uF (475) Electrolytic + towards Pin 2) IN SERIES to/with R40 - R40 to a 47ohm and pull R72 - it can work, just this device isn't for the Cobra 25/29 using the 2005 chip - feedback and biasing is different for those.

    I'm referring to my schematic for that 2030 conversion - the output "floats" due to internal regulation - so the output has a DC bias, which returns to the Pin 2 of the IC, don't try to shunt it (R72) for it will drive the thing to clip because of the DC offset bias is pulled low, it will try to push it back up - ruining your effort.
     

    Attached Files:

    Shadetree Mechanic likes this.
  7. Uncle Ronnie 336

    Uncle Ronnie 336 Active Member

    Joined:
    Apr 28, 2020
    Messages:
    73
    Likes Received:
    27
    Very good thank you for the info. I will let you guys know when I order that part what the translation of that circuit comes out to on this radio.
     
  8. Uncle Ronnie 336

    Uncle Ronnie 336 Active Member

    Joined:
    Apr 28, 2020
    Messages:
    73
    Likes Received:
    27
    Also if anyone is watching this has this model radio please send it to Handy Andy (and pay the guy if you get the radio back screaming)
     
    Shadetree Mechanic likes this.
  9. Uncle Ronnie 336

    Uncle Ronnie 336 Active Member

    Joined:
    Apr 28, 2020
    Messages:
    73
    Likes Received:
    27
    Locals here just tend to find a cheap radio at a tag sale or on eBay not always knowing what they are buying. The 4x4 Bros tend to prefer smaller sized radios.
     
  10. 9C1Driver

    9C1Driver Sr. Member

    Joined:
    Aug 13, 2008
    Messages:
    3,490
    Likes Received:
    1,313
    There are some Jeep and 4x4 camping locals that had good luck adding a KL60 or KL203 to the smaller cb radio's. The Uniden 980 and 122xl were the choice for the few that also wanted SSB.
     
  11. Uncle Ronnie 336

    Uncle Ronnie 336 Active Member

    Joined:
    Apr 28, 2020
    Messages:
    73
    Likes Received:
    27
    Yeah unfortunately the bearcat 980 is roughly the size of a Cobra 29. I have one in my truck.
     
  12. Uncle Ronnie 336

    Uncle Ronnie 336 Active Member

    Joined:
    Apr 28, 2020
    Messages:
    73
    Likes Received:
    27
    :: UPDATE:: I*R 520 FET has been dropped in and now I have about 3.25w carrier, and 25w peak! This little junk box is SCREAMIN with an 80s realistic microphone. So I'm thinking I will be making the checklist for this model radio. A 4pin Cobra wired microphone connector is getting slapped on and I'm thinking I might order a ranger SRA 198 for a microphone. I basically rebuilt the whole driver and final stage.
     
    Handy Andy likes this.
  13. Handy Andy

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

    Joined:
    Apr 23, 2018
    Messages:
    4,536
    Likes Received:
    5,563
    AWESOME!

    Glad you kept at it!
     
  14. Uncle Ronnie 336

    Uncle Ronnie 336 Active Member

    Joined:
    Apr 28, 2020
    Messages:
    73
    Likes Received:
    27
    The vishays were alright, but the I*R def gave me a couple more peak whiskeys
     
  15. Uncle Ronnie 336

    Uncle Ronnie 336 Active Member

    Joined:
    Apr 28, 2020
    Messages:
    73
    Likes Received:
    27
    Stock vs. hot.
     

    Attached Files:

    Shadetree Mechanic likes this.

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!