Obsolete challenge...

Discussion in 'Wireless & RF Design' started by PackratKing, Jun 26, 2014.

  1. PackratKing

    Thread Starter Well-Known Member

    Jul 13, 2008
    850
    215
    Greetings Gals and Guys !!

    I usually hang around pestering the people on GenChat... Now it's your turn :D

    I have an age-old Audiovox 40 channel CB radio, -- Model MCB5000A that the prior owner tells me *works*... though he was in a hurry to retrieve it from a car being junked, and chopped the power-in Noise-out wiring, and there is no "roadmap" anywhere on the unit..

    Edit : Checked google to see if old "Sams" manuals would have anything , they do, for a fee, tho' I think it may be worth it for the whole schmere... does any one have the wiring roadmap ???

    Thanx in advance ......PICTURES ARE NOW IN # 13
     
    Last edited: Jul 2, 2014
  2. vk6zgo

    Active Member

    Jul 21, 2012
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    Are there wire stubs left that you can investigate?
    The speaker wiring usually looks a bit different to the power stuff,which is normally thicker,with one lead being Black,or Red with a Black stripe.

    Many CBs have a diode connected across the incoming supply wires.
    It is normally reverse biased,but if you connect the supply backward,will
    conduct,blowing the fuse which is normally in the external wiring.

    Hang your DMM across the wires in the diode position,& if you see one,that is pretty much certain to be the power connection.
    When you then connect the supply,make sure that it is in the polarity that doesn't show diode conductivity.
     
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  3. vk6zgo

    Active Member

    Jul 21, 2012
    677
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    But wait! there's more.:D

    For some strange reason,CB radios are wired so you can't hear the receiver unless a microphone is plugged in.(Remember this when you get to the point of a receiver test)

    From memory, this is done by simply looping the speaker connection through a loop in the mic,so you can probably see continuity between one of the speaker leads & a pin on the mic socket.

    Another point is,a lot of CBs are similar,so if you can have a look at the connections of another brand,you may be "good to go".
     
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  4. BR-549

    Well-Known Member

    Sep 22, 2013
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    Breaker one nine. Hey good buddy.....I'm not sure what "power-in Noise-out wiring" means. And I have never seen a cb that you couldn't listen to without a mic plugged in. It has been quite a while, but I have been in a million cbs. Can you show me general pics of unit and a close up of where "power-in Noise-out wiring" is missing? Maybe I can help you out.
    Your turn.
     
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  5. Art

    Distinguished Member

    Sep 10, 2007
    785
    61
    Power in - speaker out? Though it should have a speaker inside it.. PA maybe?

    I thought it was going to be some "usage of obsolete gear" thread, and was ready to get started. Damn!
     
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  6. BR-549

    Well-Known Member

    Sep 22, 2013
    2,004
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    Rodger dodger Art, do you mean the power connector is missing? That should be easy to take care of. br-549 on the side.
     
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  7. Art

    Distinguished Member

    Sep 10, 2007
    785
    61
    I'm assuming the OP has four wire pigtails and doesn't know which is which.

    If we get a pic with the cover off there will be no mistake.
     
  8. alfacliff

    Well-Known Member

    Dec 13, 2013
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    some of the audiovox radios were in dash mounted am fm cassette and cb combos. the wireing on these was a mess, however, I have a large pile of sams cb photofax at home. possibly I can scan the page on the wireing connections when I get off work and home this evneing. other than that, I have never heard of a cb with an external speaker that was hardwired to the radio.
     
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  9. alfacliff

    Well-Known Member

    Dec 13, 2013
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    and if you check the cobra 19 (all versions) it would not recieve without the mic, but the cobra 29 would, along with all other relay switched radios.
     
  10. vk6zgo

    Active Member

    Jul 21, 2012
    677
    85
    Vey common among CBs in Australia----can't remember seeing any that didn't need the mic.
     
  11. vk6zgo

    Active Member

    Jul 21, 2012
    677
    85
    Good point about the internal speaker,alfacliff.
    Maybe he had it set up as a PA---always thought that was a silly idea,though!
     
  12. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
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    the external speakers and pa speakers plugged in
     
  13. PackratKing

    Thread Starter Well-Known Member

    Jul 13, 2008
    850
    215
    FWIW... Art Yes, there is approx 1 1/2 " of all wires left protruding, and you likely know that this model has the channel selector in the mike... whether a power mike I haven't investigated yet... I've had this languishing in a box on a shelf for years, and need to get it rolling for a drive across country in the near future...

    The long red wire, hanging down, has half of a fuseholder on it, so I assume a + power connect... The original wiring sticker is useless...

    The insides all look good and clean.. The mike socket is in the upper right of the PCB pic.... last is the unit ID tag...
     
    Last edited: Jul 6, 2014
  14. vk6zgo

    Active Member

    Jul 21, 2012
    677
    85
    How many wires come out the back?
    What colours are they?
    Are there a black & a red wire which are thicker than the others?
    Have you tried the "diode test" trick?

    What can you see if you take the cover off?
     
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  15. vk6zgo

    Active Member

    Jul 21, 2012
    677
    85
    It looks like it is one of those ones that alfacliff mentioned in post#8.

    Can you trace where the red & black wires go inside,or alternately,do the "diode test" trick I mentioned in post#2.

    Is there any sign of an internal speaker?
    Does it have a microphone socket?

    Some general pictures of the front,sides,& back of the thing may be helpful,so we can get an idea what it looks like complete.
    (Just stick the lids back on temporarily)
     
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  16. PackratKing

    Thread Starter Well-Known Member

    Jul 13, 2008
    850
    215
    :eek:
    This one is a plain radio... No casette... Any literature you could offer would be greatly appreciated... I am light on pictures, not wanting to tie up a lot of space...

    The radio does have a jack on the rear, labelled extension speaker...

    Whether that is for a PA, I won't speculate... b'cuz a PA is the absolute last thing I need in my truck, :D for some unknown reason... :D
     
  17. BR-549

    Well-Known Member

    Sep 22, 2013
    2,004
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    Could you take one more picture? I would like to see the front panel clearly. I have never seen a cb only radio with that many wires. It's a mystery to me.
     
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  18. vk6zgo

    Active Member

    Jul 21, 2012
    677
    85
    I've never seen one like that,either!
     
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  19. PackratKing

    Thread Starter Well-Known Member

    Jul 13, 2008
    850
    215
    Yes... I will get a pic in here asap... As shown, the only thing on the front panel is the multi-function mike jack...


    Edit: YES BeerBelly, you are right... ALL CONTROLS ARE ON THE MIKE.. pic.
     
    Last edited: Jul 13, 2014
  20. BeerBelly

    New Member

    Dec 16, 2013
    29
    5
    From the picture you provided It looks like one of the CBs that have the
    volume control, squelch, channel selector, and readout built into the mic.
     
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