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Peavey 400BH Module Power Supply Project

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  • Peavey 400BH Module Power Supply Project

    MEF members and Visitors...

    With a day off and waiting for schematics and parts on other fixes, I finally got around to one of my projects. I had parts to a Peavey 400BH board and power transformer 705-18715. The goal was to cut the PC board and salvage the components for the dual power supply (+50, -50, +15, -15). I will be using this for misc projects in the future (and one of those being a small Class D amp project for learning).

    As you can see, I found a logical place to run a hack saw through the board. The cut point did not include CR28 and C41 (used for the 7815 Positive Regulator) and CR29 and C42 (used for the 7915 Negative Regulator). So I had to drill holes, mount those components, and run them to the proper trace. I decided to use new caps and diodes - the old ones had short leads. For those who know this board well, I removed some of the pins on the molex connectors and those will become my outputs. On the bottom side of the board, I cut some traces, added jumpers were needed - and in the end, I have the High and Low supply circuits in tact. Yes, I have +15 and -15 coming off CR20 and CR21 respectively. BTW, I also included a Ground connection between the transformer to the circuit board. Some Peavey amps have a single black wire connecting from the transformer case to the circuit board. This one did not - so I added it. Photo and Schematic attached.

    So... it all works fine. I have +50, -50 and Ground (on the top set of pins). I have +14.8, -15.6, and Ground on the bottom set of pins. I will debug the difference in these two voltages. It is an interesting difference since I have +27 and -27 feeding the respective regulators.

    Now that this is working, I will look for a project box or platform to mount it - including On/Off Switch and Fuse.
    Attached Files

  • #2
    Cool. Nice work, Tom. FWIW, there are cheap class D power amp modules on eBay that work pretty well. I used one for the repair in this thread.
    "Yeah, well, you know, that's just, like, your opinion, man."


    • #3
      Thank you....

      I need to add some pins for the plus and minus 15 volt points (off the high supply at the Zeners CR20 and CR21). Funny thing is, this came from a Peavey XR600C Mixer Amp. I have no idea where they used the plus and minus 16 volt supplies!! I am looking at that schematic carefully.



      • #4
        I have no idea where they used the plus and minus 16 volt supplies
        "Can't see the forest for the trees."

        Look at the whole schematic. The layout shows traces, so you can still follow them even after cutting the board. The two IC regulated supplies go only to the connector for the preamp. The two zener supplies are used only by the power amp circuits.
        Education is what you're left with after you have forgotten what you have learned.


        • #5
          Thanks Enzo...

          I looked at the board layout more carefully and see the Regulated Supplies go to the molex that jumps over to the preamp. I guess at first it was confusing because I saw "16" volts on the schematic. That makes perfect sense now.

          Duh on me!!


          • #6
            If you look at the IC regulators you will see each has a diode in the ground leg. This raises the 15v output almost a volt. SO that is a 16v supply. Technically. Unfortunately they were not consistent, drawing the 15v and 16v as all 15.
            Education is what you're left with after you have forgotten what you have learned.


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