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Electro-Voice EKX-15SP Powered subwoofer

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  • Electro-Voice EKX-15SP Powered subwoofer

    I'm working on an EV EKX-15SP that came in with a description of no power. I pulled the power module from the enclosure and put that on the bench. I then began checking for any obvious signs of damage or blown fuses. No visible damage was seen. There's an internal fuse and it is ok. Since there is no schematic available, I started looking for any test points on the board. As you can see, there is lots of goop on the board.

    I was able to get some readings:
    VBUS read 327VDC
    PSUSW reads 164VDC
    +/-15VDC supplies are good
    +/- 53VDC test points called +VP and -VP on the middle section of the main board.
    VSW1 and VSW2 read -0.39VDC.

    After probing around a few pads on the signal board near the LED screen that weren't marked, I was able to find my signal thru my signal tracer. I then checked with an input signal and I'm getting power and signal to the output terminals (no speaker or load connected at this point).

    Speaker terminals have no DC voltage on them.

    System DSP settings are all default, and the Master Volume is at 0dB. It can go up to +10dB, but I was testing this on the 0dB setting first.

    Now, with 1VAC rms 100Hz sine wave applied at Input 1, with a 0dB on the Master Volume pot, I get only 16.8VAC sine wave on the output driving a 6.8ohm resistor. The subwoofer speaker is 8ohm. This is better than a no power condition, but I'm thinking it seems weak. Same thing using Input 2.

    This unit calls itself 1300W, with the manual saying that the power consumption is 1.8A, with a note that it is at 1/8 of the power. Quick calculation leads me to believe that the unit should then be capable of 162W (1300/8). With a 1VAC input, I'm only getting 42W. What input level should I be inserting to get full power?

    Looking for any suggestions on what to look for next. Thanks!
    Attached Files

  • #2
    Have you tried a factory reset?
    "Yeah, well, you know, that's just, like, your opinion, man."

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    • #3
      Good suggestion, Dude! Just did the factory reset. Originally I didn't as all the settings appeared to match the defaults.

      Now with 1VAC input, I get 24.7VAC output, much better. But, as the output gets higher (above 16V), you can hear a tiny click and the output drops out momentarily then comes back steady. I did notice that the fan never turns on. I tested the fan by applying 12V directly to the fan leads and it spins without issue.

      Any idea how the fans on these are controlled or what might be momentarily dropping the signal? I'm trying to determine if the momentary signal drop is my function generator going between notches, but if so, I would have expected that to happen at the lower levels as well.

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      • #4
        I'm not sure about fan operation on those. It's likely either controlled by heat or could be input level. I've had only one of those come into the shop that needed amp repair, so far. EV wouldn't supply a schematic and the unit was still under warranty, so they simply sent out a new plate amp for swap. I didn't really dive into it too deeply. The only other thing I've done with those units is some driver replacement. One thing you might do is check the resistance of the speaker. I did have a near shorted voice coil in one of the units that was causing the amp to go into shutdown. Or, temporarily try the amp with a different speaker and see if it still has problems.
        Last edited by The Dude; 05-18-2021, 11:32 PM.
        "Yeah, well, you know, that's just, like, your opinion, man."

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        • #5
          Thanks again, Dude! I did measure the speaker and its DC resistance was 7.9 ohm. Seemed a little high for an 8 ohm speaker, but maybe it's ok. It definitely wasn't a short or open circuit.

          Got another question, what would be a normal input level to achieve full power on these? Is 1V considered too high, normal, too low?

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          • #6
            There is a clip indicator on one of the screens that will tell you if there is too much input signal. If I recall correctly, you can also set up a limiter in the DSP section.
            "Yeah, well, you know, that's just, like, your opinion, man."

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            • #7
              Great info, as always! I'll check that out and let you know.

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              • #8
                Whatever they may call it, I'd think to test power output, you want the master set all the way up.
                "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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                • #9
                  After additional testing, the amp was not producing enough power and was cutting out. I contacted another store that is an EV dealer and talked with them for a long time. Even they are not able to get schematics from EV. Got a price on a replacement module, but the customer elected to pass on the repair.

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