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  • #1

    behringer pmp5000

    i see this mixer is known for this, so here it is channel b blew out, so i replaced all the output transistors on that side (channel b) powered it up and the main power transistor on channel a blew. to make a long story short i ordered all new replacement transistors but on the speakon pcb board (pm out) 2 current sensing resistors seem to have blown, C3 and L1.
    i ordered replacement power transistors but i dont know the value of C3 and L1.
    schematics for this thing are hard to find
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  • #2
    Well, C3 and L1 would not be resistors.

    Even if you had the factory schematics, the Speakon board is not in them. First thing I would check on there is for a shorted triac. I am working from memory, ther is a TO220 triac on each speakon out is there not? As to what those smaller parts might be, all I can suggest is read them off the undamaged side.

    IS hot shorted to ground on either speakon out?

    When you rebuild the amp module, connect your bench speaker or test load right to the wires, leave the wires off the speakon board to verify function.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      theres nothing stamped or printed on ant of the current sensors.
      the speakon terminals are not shorted anywhere, but i will try to test it with the speakon board bypassed.
      thank you for your help.

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      • #4
        Can't help you, that speakon board is not covered in the schematic set. That is the case on most of their amps. Well, there is a series inductor on the PMH200 output that is 3uH. I bet that would work here.

        Don't know about C3, can you determine looking at the one for the other channel?
        Education is what you're left with after you have forgotten what you have learned.

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        • #5
          Speakon board blown.

          I have identical fault on my PMP3000. I firstly replaced 2 diodes in the SMPS and a wire wound ceramic resistor, and switched it on without connecting the power amp or mixer top. Super result, I measures the output voltages which will supply the power amp and mixer top and they are also spot on.
          Now....when I connected the power amp, ......POP.....goes the wire wound ceramic resistor (22ohm) so replaced that again, and dismantled the Power Amp to find IRFP250N was completely shorted at all pins. I replaced that and had another go....GREAT, it fires up wonderfully, that is...through the headphones and channel A into a PA speaker....but sounding like a toasted output transistor on channel B.
          I decided to change all 4 IRF9640's. Still had the same result, so thought I would try changing the Red/Black wires from speakon A to output B. Here is where the fault was. After taking out the Speakon module, I discovered an exact image as the previous thread.
          The question is, what effect will it have on the amp running the PA speakers straight onto the wires bypassing the speakon socket and once again, what exactly is L1. I'm sure it's easy to say....don't need it!!!!!!..is it fused thermal link....I can measure the capacitor easy enough by simple comparrison to output A's cap's 4,5 and 6.

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          • #6
            We have determined that the inductor is a 3uH with a 22 ohm resistor in parallel. it is in series with the output and serves to keep the amp stable. The zobel stability network is a 22 ohm resistor and 100nf cap in series ACROSS the output. These are critical to the stability of the amp. If you bypass those parts, you run the risk of the amp going into oscillation and burning itself up.

            And check for triacs across each speakon output. They have put protective "crowbar" triacs there to short the output when DC is detected. This is done to prvent your speakers from CATCHING FIRE. When an amp channel blows, itoften shorts out the triac, which must be replaced.
            Education is what you're left with after you have forgotten what you have learned.

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            • #7
              Behringer Q05-56506-10277

              Thanks for the information there. Can you help me and give me an exact designation of that part so I can order one. When I look up 3UH inductor, I don't really get anywhere. The surface mount caps are simple to source. I see that I can buy the whole PCB (as designated in the title of the thread) in the States for $26 but the shipping is a crazy £300...get that!!!!
              Can you send me a link which shows the L1 in some online catalogue, I'd really appreciate it. By the way, channel A comes out really great and when I swap over channel B wires onto channel A on the speakon board, it also sounds great....it just comes down to replacing that Inductor and blown cap. Please help.
              you can send link to saranden@yahoo.co.uk.....

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              • #8
                before settling on a parts order, on that burnt channel PLEASE check for short across the speakon. The jack itself won't be shorted, but the triac across it might be.

                Mouser lists the part, stock #: 875-CM3322X630R-10

                The part is a Steward CM3322X630R-10. Mouser shows them as on-order, out of stock, expecting shipping the end of this month.
                Education is what you're left with after you have forgotten what you have learned.

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