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Thread: Altec Models 4/6/8 (Model 9813B) "Automatic Power Control" Crossover schematic

  1. #1
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    Altec Models 4/6/8 (Model 9813B) "Automatic Power Control" Crossover schematic

    Hello, anybody familiar with the Alec Model 6 also called the "9813B Monitor Loudspeaker) ?


    The crossover has the "Automatic Power Control" that has a passive bulb that lights up to indicate when the power control is about to lower the speaker volume to avoid "excessive power"

    The "Network Assembly" has a part number 35490 (listed on pg-2 of the Model 9813B Brochure) although the PCBoard from my speaker has part number 21-06-045479.

    I was hoping someone may have some information on this.

    Thanks

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    I've never seen this particular model but the light bulb in series with a speaker driver is a widely used trick to prevent burn out. As the current thru the bulb rises the resistance increases and the bulb lights up turning the excess power into heat and limiting the current flow to the voice coil.

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    Thanks

    Thank you for that bit of info.

    Hopefully someone has the schematic.

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    Are the components potted in tar or something that prevents you from simply reconstructing the crossover schematic from the crossover in hand? Even complex passive networks are fairly simply electrically. This drawing is from a B&C suggested crossover for one of their coax drivers that uses 12V automotive light bulbs in a protection configuration.

    Quote Originally Posted by Brick View Post
    Thank you for that bit of info.

    Hopefully someone has the schematic.
    Attached Images Attached Images  

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    Riley,

    No, the board is crystal clean (no potting of any kind) I need to get off my butt and draw this thing out on paper.

    Heck, it's only;
    3 Capacitors,
    4 hi-wattage resistors,
    1 circuit breaker (based on the printing on the board "CB-1",
    1 incandescent bulb
    4 transformers (inductors)

    But there is one component marked "W-1" that looks like a diode, (non-glass type, no markings at all) Looked up that designation "W" online and only found it stands for wire. So I am not sure what that item is.

    Thanks for your reply, I will get out my drawing board and make a nice schematic sketch before reinstalling it into the cabinet.
    I really like the sound of these speakers and want to make them last a few more years.

    So far I've had this work done; re-edged the woofers, re-coiled 1-mid, and replaced 1 of those kooky "Manta-Ray" tweeters. (found a working pair on Ebay)

    Cheers

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    Post a picture of the network with the mystery part and perhaps someone will recognize it. Maybe someone got too enthusiastic about zener diodes. Stranger things have happened.

    Quote Originally Posted by Brick View Post
    Riley,

    No, the board is crystal clean (no potting of any kind) I need to get off my butt and draw this thing out on paper.

    ...
    But there is one component marked "W-1" that looks like a diode, (non-glass type, no markings at all) Looked up that designation "W" online and only found it stands for wire. So I am not sure what that item is.

    ...

    Cheers

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    Attached photos of crossover, front and rear.
    Attached Images Attached Images   

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    The photo of the component side still has the plastic panel installed.

    I will upload another photo of the board without panel.

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    W1 is a jumper allowing Altec to change configurations easily. Literally a piece of wire with a plastic sleeve around it. When you diagram the crossover you'll find that it shorts something out or connects something differently than it would if the jumper was in in the W2 position.

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    Riley,
    Yes, so in this case "W" is correct. Meaning a wire.


    I am starting to learn about drawing schematics. Takes a bit of forethought instead of just drawing a paper copy of the traces on the board.

    There are a couple of good primers online I have seen so far.

    A new adventure!

    Now to find some good poly caps to replace the old Callin ones on the board.

    Thanks again!

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