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Browning Mark 4A receiver-socket follies.

Discussion in 'CB Radio Modifications' started by nomadradio, Jul 6, 2018.

  1. nomadradio

    nomadradio Analog Retentive

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    Ah, the Browning Mark 4A.

    So, just exactly why does it take two cabinets? Every Browning base radio before the Mark 4 had a separate transmitter. And they were all true transmitters, each with its own separate AC power cord. You could plug it up and transmit without the receiver. Not sure why you might want to, but there it is.



    The Mark 4 was different. The receiver contains the one and only power transformer for this radio. It powers every function in the transmitter. No AC power cord, just the fat 10-conductor cable. Won't do one thing but hold down the desk without the receiver. And without a power transformer in it, the desk might need more ballast than that alone.

    And that's the subject of today's annoying bad habit. The way some folks will decide to "clean" the blades on the transmitter's 10-pin plug.

    The type 310 Cinch-Jones connector's contacts are made with some sort of shiny electroplating over the brass body of each blade. This is a pretty thin layer. If it is allowed to oxidize in a humid environment, you'll get a haze on the surface that a solvent just won't remove, no matter how hard you scrub. This plug will have to be replaced, you say. That 'haze' is just the metal that used to be so shiny, now converted to an insulating compound. Oxygen and humidity, most likely.

    But hope is eternal, and this guy didn't just pull out the sandpaper. Looks as if he used a file.

    [​IMG]

    This exposes the brass base metal of the blade. It will oxidize regularly, and you will find yourself pulling it out to clean again every few weeks or less.

    This guy took the other approach. The plug was cutting in and out when you wiggle it, so he plumped up the blade surfaces with some solder.

    [​IMG]

    This wallows out the spring contacts in the receiver socket. Makes the problem worse soon if not right away. The receiver that this got plugged into now has a new socket, as well as the new plug.

    But wait, you ask. I have a Mark 4, not a 4A. It has a plug that looks like this.

    [​IMG]\

    This "Molex" connector was a fatal flaw. If yours looks clean and white like this one, it's probably because the transmitter failed before any wear and tear occurred. This connector uses tiny cylindrical pins with a diameter of .063 in. Too small for the current load on the heater and ground pins. The plug heats up, darkens the white plastic, and begins to cut out. This is one basis for the legendary "poof chip" fault in the Mark 4. If the ground connection comes loose, those chips can get their polarity reversed. Even if this occurs for only a tiny fraction of a second while you wiggled the plug, it's long enough to fry one or more chips. And the Mark 4 has a lot of them.

    We have had a long-standing policy that no Mark 4 radio goes home fixed with that white-nylon Molex connector still on it. Any radio that's going back on the air gets converted to the larger, flat-bladed "Jones" plug. And socket.

    Browning came to their senses, and the last Mark 4 radios built had the Jones plug. And every genuine Mark 4A had this connector.

    Nothing lasts forever, and we seem to replace a higher percentage of these Jones plugs than we used to.
    But if you look at one of these radios with a chance of buying it, take a close look at this plug. But if the plug looks bad, there's a good chance that the socket where it was plugged in will also have enough wear and tear to merit getting changed out. Shiny, clean contact surfaces are always a good sign for anything that's 40 years old.

    73
     

  2. Klondike Mike

    Klondike Mike Well-Known Member

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    Thanks for the info. I've got a 4 here that somehow ended up with a 4A badge. I checked my "Jones" and it looks pretty good!

    [​IMG]
     
    Shadetree Mechanic likes this.
  3. nomadradio

    nomadradio Analog Retentive

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    The laminated badge tells you it was converted to a 4A. Most likely by Phil Nichols in the 80s or 90s. He provided factory service after Browning closed down. The only way he would repair a Mark 4 was to convert it to a 4A.

    The transmitter should have the single-chip channel selector/display board and a MC145106 chip on the PLL board.

    Once that has been installed, it's not a "4" any more. And when the surface of the plug's blades goes from 'shiny' to 'fuzzy' it's time for a new plug.

    73
     
    Shadetree Mechanic and Dmans like this.
  4. Dmans

    Dmans Well-Known Member

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    I have been half heartedly looking for a replacement Jones plug and socket for the Regency Range Gain restoration I am considering. It is an 8 pin with the male plug on the chassis and the female socket on the line cord. (4 horizontal and 4 vertical pins on each half) Can't seem to put my eyes or hands on an exact replacement for this and am considering other options. I would like to change it to a 3 prong cord as well. Don't know that I will need all 8 pins as it won't be 12vdc powered. Any ideas?

    I had Phil's number around here awhile back(1990ish). He supplied me with a new channel 16 transmitter crystal for the "tricked out" MarkIII that I had (for a short time until the next radio called!). Nice guy too! Is he still around?

    73's
    David
     
  5. nomadradio

    nomadradio Analog Retentive

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    The Cinch-Jones type for this one would be "S308CCT".

    An Ebay search for that number showed nada.

    A search on "Jones Plug" turned up every size and gender but that one. Plenty of the male-side "P308" cable and chassis-mount to choose from.

    Did find this on page two of the search.

    https://www.ebay.com/itm/Power-Plug...771048?hash=item569d82a028:g:kbkAAOSw4shX~stU

    Combo deal for the plug and socket both is the closest I found.

    Here's another, much cheaper. Pretty sure the one with the cable clamp is the female socket side.

    https://www.ebay.com/itm/2X-12pcs-T...901773?hash=item3d6b76054d:g:19MAAOSwweRbPRyl

    Lost patience at page four of the search.

    73
     

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