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Thread: Carvin AC120S Power Distribution/Filter (yes, not technically music electronics)

  1. #1
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    Carvin AC120S Power Distribution/Filter (yes, not technically music electronics)

    I've had a Carvin AC120S rack power distribution module for about four years. It's your basic Furman/Juice Goose type thing with one wrinkle - each outlet has its own on/off switch on the front panel, and it has a sequential mode where it will turn them all on or off in sequence with a delay (you have several delay choices) between events.

    It has recently started behaving oddly. It very often activates more than one outlet with a single button push. For example, I'll push button 1, and it powers up. I'll then push button 2, and outlets 2 through 8 simultaneously fire. It will do this whether I'm manually turning them on, or if I use the sequential feature.

    Some observations:

    • It only happens if the device which is being fed is powered on
    • If the device being fed is powered off, frequently when it is powered on, other outlets will activate
    • I have not exhaustively tested this, but it appears as though this behavior does not occur if the device powered is not in the rack with the power supply.


    The pushbuttons actually fire relays, which pull in to activate the outlets. What appears to be happening is that either the inrush from the powered device somehow screws with the control logic, or (since it appears not to happen when the devices aren't racked) some sort of EMF from the device powering up does a similar thing.

    I generally have four items 'in play' - a wireless receiver, an Axe-FX, and two powered monitors. The only one that drives this behavior is the Axe. And it doesn't matter into which outlet it's plugged, or in what order outlets are activated.

    Nothing has 'changed' recently to explain this - it's the same set of components I've used for years.

    Any ideas?

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  2. #2
    Supporting Member Jazz P Bass's Avatar
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    While the outlets may appear to be relay activated, they are controlled by a microprocessor.

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    Quote Originally Posted by Jazz P Bass View Post
    While the outlets may appear to be relay activated, they are controlled by a microprocessor.
    Yes...a microprocessor which fires relays.

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  4. #4
    Supporting Member Jazz P Bass's Avatar
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    So check the microprocessor supply pins.

    If it has power, check that the inputs are valid.

    If they are, then check the outputs.

    Somewhere in there it's getting goofy.

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    Lifetime Member Enzo's Avatar
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    Regardless of how it seems, from the description, a real likelihood is the actual push buttons are intermittent - excess "contact bounce" is happening. In other words, you press a button once, but it sends several pulses through the circuit.

    The logic probably runs on +5vDC, so checking that for level and ripple is a good idea too.

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    Contact bounce is making a bunch of other contacts bounce too?

    That doesn't make sense.

    I appreciate the advice, but it seems like you're ignoring a lot of symptoms. It NEVER happens when the devices attached are powered off. And it nearly always happens - or I can make it happen - when they are.

    I've found some references to other people having the same problem - Carvin basically told them "we'll sell you a new one for half price". Carvin has ignored me, FWIW.

    The most common 'mode' of failure is, I press button two (which turns on the Axe-FX), and buttons 2 through 8 fire (apparently) simultaneously.

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    I've found the problem - not the root cause, but enough to fix it.

    Carvin wired the outlets 'backwards' - neutral to 'short' blade. Correcting this appears to have resolved the problem; I can only assume that some interaction with grounding in attached devices causes some kind of 'problem' for the logic controller.

    Carvin's assembly is...odd. Crimp spade terminals to wire, push spade terminal onto outlet, SOLDER spade terminal to outlet, shrink wrap over all of that...why bother with QDs when you're just going to solder them anyway?

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  8. #8
    Supporting Member Jazz P Bass's Avatar
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    My take on the disconnects is it would be easier to solder them at assembly as opposed to a simple wire.

    Plus, you do get the added terminal to blade connection.

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  9. #9
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    My point is, why solder at all?

    I worked for the DoD for years in aircraft wiring and electrical distribution. If terminal connections are acceptable in F-18s, I think they're OK in consumer-grade audio.

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  10. #10
    Supporting Member Jazz P Bass's Avatar
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    I do agree that it is a bit of overkill.

    In fact, a high current condition would in all probability cause the solder to melt.

    F-18's?
    Cool.

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  11. #11
    Lifetime Member Enzo's Avatar
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    If your mains wires are getting so hot as to melt the solder, you have serious problems.

    Crimps allow them to make up a complete harness, which an assembler can then install in a couple minutes. As to then soldering the crimps, it may be overkill, but if it makes them feel better...

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  12. #12
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    AC120S

    Check the electrolytic filter caps...common failure on this unit

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