Pioneer VSX-7500s voltage selector

Discussion in 'Pioneer Audio' started by Vintagehunt, Feb 4, 2019.

  1. Vintagehunt

    Vintagehunt New Member

    Greetings to all ,

    Picked this up from someone and I need a little help to sort out the wiring.
    I got it home and started cleaning it from inside i saw 2 blown fuses and noticed a problem .

    The voltage selector switch on the rear of the unit has the knob missing and exposing the internal contacts. The switch part number is AKX-507. Apparently it’s a common fault of these switches to just fall apart. My problem is to get this thing going so I can use it and I don’t want to spend $ for a simple switch but instead just go ahead and hard wire it for 220 volts.

    Please check the attached schematic and guide me , any help i would be grateful .


    Attached Files:


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  2. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Glen Burnie Md.
    Looking at the schematic it looks like Pin 2 (@ about 1:30 o'clock) and the next clockwise pin (at 3 oclock) are tied together, and pin 5 7:30 oclock) and the next clockwise pin (at 9 oclock) same thing. Let's get someone in here that reads them better than me and either refute my reading or verify it. The voltage setting appears to be between the pins that get connected by the switch leaves for each voltage spread. If your wall voltage is higher than 225v or so, I'd change it to 240V. It won't hurt the unit, and it'll keep the transformer from heating excessively from overvoltage.
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  3. Vintagehunt

    Vintagehunt New Member

    Thanks , i figured out which pins on the selector to have 220v they are 2 + 5 on the selector itself also the 127v (3+6 , 1+4) so i replaced the blown fuses and tested it on 127v one time and another one on 220v , both voltage input i got dim display with all front panel working fine and speakers relay not open .

    so my conclusion i think the first owner when the voltage selector fail apart maybe it was on 110v or 127v and he connected to 220v which cause a power transformer failure .
    am i right ?
    Last edited: Feb 6, 2019
  4. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Glen Burnie Md.
    Check the individual transformer Windings with a Ohmmeter.

    Check at the selector
    Pins 6 & 4 (bottom 120 winding)
    Pins 6 & 5 (Bottom 110 winding)
    Pins 3 & 2 (Top 110 winding)
    Pin 3 to Transformer wire # 7 (top 120v winding) Wire #7 goes off to the unit. I haven't looked at the full schematic so you'll need to sus that one out. Also Check each pin with the meter set to ohms against chassis ground (red probe on pin, black probe on CLEAN SHINY CHASSIS GROUND (preferably clamped)).

    I just looked at the FULL SCHEMATIC. There is a 120-240 selector switch nearby (probably on the power supply board) that needs to be set to either 120 or 240. This may be set to 120. Check it for correct orientation. But I'd DO THAT LAST after checking the Transformer windings. This switch is on the left side of this schematic (S2- AKX1004).
    ScreenHunter 85.png
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  5. Bob

    Bob AK Subscriber Subscriber

    West coast
    at first glance, correct me if i'm wrong.
    pin 7 (going to the left as one part of the AC feed)
    pin 5 (the other side of the top transformer secondary) goes to pin 3 of the switch
    pin 3 of the switch goes to pin 6 of the switch (fuzzy but I think it's pin 6)

    then pin 6 of the switch goes to the 0v or pin 2 of the bottom transformer secondary.

    this means the two secondary transformer "grounds" (the 0v setting) to each other

    then pin 4 of the bottom secondary transformer tap goes to pin 4 of the switch
    pin 1 of the switch also goes to the left and is joined by the switch at the far left.

    common ground pin 2's (both transformer secondaries) go to pin1 with a fuse
    and then to the AC socket at the far right bottom.

    this means that for the switch settings this is set for 120v.

    you should be able to rotate the switch clockwise to get to 220v as per the label
    diagram at the center top.

    then follow the transformer and switch pin settings to verify.

    you could also set the switch at various settings, measure the resistance
    and 220v should be the second most resistance measurement, 240 being
    the highest, and 110 being the lowest.

    do all checks and if you have access to a step-down transformer then you can
    live verify BUT

    IFF you are aware that any AC voltage can and will be deadly. do not count
    on steady hands for probe use - use clips. stuff left hand in pants pocket.
  6. Vintagehunt

    Vintagehunt New Member


    Thanks for the details , i really appreciated but i couldn't get any reading by that way , i only got ohm readings on the output pins (while it's off) and yes there's another switch for 120-240 it's for the standby transformer .


    Yes you are correct but the selector is damaged already and can not rotate !!
    that's why i need to hard wire it from the rear pins .

    Attached Files:


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  7. Bob

    Bob AK Subscriber Subscriber

    West coast
    visually move the selector clockwise two stops (print out a copy and
    use a red marker to do this) follow the wires (wo and only two
    wires shorted by the selector switch and two such sets) from the selector
    back to the two separate transformers and their respective posts. id
    each set then list and mark the two posts to be tied together.

    then post that picture, and using a different color marker indicate
    for each of the two sets of tie-togethers, which two transformer posts

    then take pictures

    and before you do anything, get a consensus from us on the plan.

    you are literally wiring two sets of two wires.

    with your posted picture we can trace your steps, determine whether
    it is correct and give you further guidance.

    do note I am oversimplifying.
    1. there are another dozen wires to review/disable
    2. the role of the other switch (2 positions) to be decided
    3. removal of broken switch
    4. the exact transformer tie togethers is the most important.
    5. your analysis, word by word, which is your thinking. what you find,
    your plan, and going forward what the whole process is. anything
    you leave out that you eventually do could destroy things. hence the
    need to completely describe things. think aircraft maintenance
    not picture of rebuilt engine. cannot overemphasize this - way too
    many destroyed audio units from incomplete descriptions or bad pix.
    Last edited: Feb 10, 2019

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