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Peavey Minx II Bass amp transformer replacement questions

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  • Peavey Minx II Bass amp transformer replacement questions

    I purchased this Peavey MINX-II bass amp with a 220V transformer, I don't own a step up transformer to be able to use it. I contacted peavey for a 110v transformer but they don't stock this item anymore.
    Can someone suggest a replacement 110v CT transformer that would match up with the circuitry? I need to supply +/-35V and +/-15V rails. Would something like a hammond 166L24(48Vac) or 166L25 (50Vac) work or other brand suggestions?
    anything else to consider?
    thank you

    Click image for larger version

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  • #2
    110v CT??? That would be 55v a side, and that would make +/- 75vDC or so one rectified and filtered. I'd say you need more like 50v CT. Or do I misunderstand?

    Oh, your possibles look more in line.

    Look at the dimensions of yours, then compare to the ones you consider. A new one has to fit in the space available and come reasonably close t0 the mounting holes.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Sorry, re-phrase, I meant to say a 110v transformer that needs a 50Vac CT output to supply the rails.
      Other than dimensions, do I need to take into account anything else because I do not have the specs of the original 110V transformer.
      webber
      Junior Member
      Last edited by webber; 01-13-2022, 03:41 AM.

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      • #4
        Originally posted by webber View Post
        I purchased this Peavey MINX-II bass amp with a 220V transformer, I don't own a step up transformer to be able to use it. I contacted peavey for a 110v transformer but they don't stock this item anymore.
        Can someone suggest a replacement 110v CT transformer that would match up with the circuitry? I need to supply +/-35V and +/-15V rails. Would something like a hammond 166L24(48Vac) or 166L25 (50Vac) work or other brand suggestions?
        anything else to consider?
        thank you

        Click image for larger version

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        166L24 and 166L25 will NOT do, they are respectively 24V CT and 25V CT , you need 48V CT or 50V CT.
        From the Hammond line, you need :
        Model: 166L50 - 100VA - 115V primary 60 Hz. - 50V C.T. - 2 Ampere
        which fits the specs,is excellent quality, but probably somewhat expensive at U$57

        AnTek has gobs of toroid transformers at excellent price, this one will do:
        https://www.antekinc.com/as-0525-50v...r-transformer/

        Somewhat tight specs but I guess (specially given Covid restrictions) that your amp will see more use-at-home type than regular club use.

        U$19 sounds like a good price

        Mounting requires a center bolt (easy) but specially a top "cup" washer and a rubber disk "sandwich" , half for electric insulation, half to protect wiring.
        I mean ask AnTek for it , to avoid ordering from somewhere else and needlessly paying extra postage.

        Click image for larger version

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        Juan Manuel Fahey

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        • #5
          Assuming there is room for it.
          Education is what you're left with after you have forgotten what you have learned.

          Comment


          • #6
            J M Fahey, I wasn't too sure of what I needed, and I looked at the Hammond line and they are expensive. So, I need to know the dimensions of the antek to see if it will fit in the chassis, anyway to find out?
            thank you
            edit: never mind, I just saw on the specs on their page.. I will check in the chassis.

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            • #7
              I'm afraid it wont fit. The original is 3" and there isn't enough room to fit a bigger one. Otherwise, I just sourced locally another transformer 54VCT (27-0-27), but I'm not sure of the output current, Would that voltage be excessive and would 2A be the Max I can use?

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              • #8
                Originally posted by webber View Post
                I'm afraid it wont fit. The original is 3" and there isn't enough room to fit a bigger one. Otherwise, I just sourced locally another transformer 54VCT (27-0-27), but I'm not sure of the output current, Would that voltage be excessive and would 2A be the Max I can use?

                Click image for larger version  Name:	Minx-II chassis.jpg Views:	0 Size:	221.2 KB ID:	949504
                I assume you mean the original one,seen from above, is 3" wide.

                Please measure ABC, both in original transformer and the one you found.

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                Please use Metric: cm and or mm

                Also measure chassis height.

                Thanks
                Juan Manuel Fahey

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                • #9
                  Be aware, on this model, the chassis slides into a small slot in the cab top, so the transformer must fit within the chassis dimensions. The Antek does look like a good deal, and it is short enough if the girth fits.
                  Education is what you're left with after you have forgotten what you have learned.

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                  • #10
                    Yes.

                    I also think the toroid mentioned "should" fit but .... but hard numbers will help us focus better, so we need them.

                    Dimensions will not only answer "space" but "ratings", go figure.

                    Please answer post #8
                    Juan Manuel Fahey

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                    • #11
                      Here are the dimensions and spacings between other components, like Enzo said this chassis slides into the cabinet so space is restricted. Also, the $19US transformer may be a good deal but the shipping costs of $33US (UPS standard) and the $50 broker fees to Canada kills the good deal, I don't think this will be a viable solution since this amp is worth about $100 CAD on the used market.. Seeing how much trouble it is to find a suitable replacement, I may end up buying a step up transformer which I think will be less headaches and cheaper solution..



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                      • #12
                        Ignoring the shipping issue for now, the Antek is only supposed to be about 40mm tall, will it squeeze under the AC cord socket?
                        Aside from that, there will be the question of the bolt sticking out under the chassis, and how tight it fits in the cab with the bolt there.
                        "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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                        • #13
                          Originally posted by webber View Post
                          Click image for larger version Name:	Minx-II transformer.jpg Views:	0 Size:	239.3 KB ID:	949590
                          Ok,you answered A (70 mm) and B (60 mm), we still need C which is the iron lamination pack thickness.

                          I am not that interested in "available space" yet but in core size, which describes power handling

                          Same for the replacement transformer you found:
                          I just sourced locally another transformer 54VCT (27-0-27), but I'm not sure of the output current,
                          And we still need internal chassis height.
                          Juan Manuel Fahey

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                          • #14
                            Originally posted by J M Fahey View Post
                            I am not that interested in "available space" yet but in core size, which describes power handling
                            Not a direct answer to your question, but this is a 35W output amplifier.

                            "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

                            Comment


                            • #15
                              Thanks, I guess itīs similar to Envoy 35, only a Bass version.

                              My questions point to" found replacement" transformer as mentioned on post #7 vs original one VA rating, which quite closely follows iron weight.

                              Being always same material, silicon steel, it will follow iron core volume, so I ask for A-B-C in mm.

                              Thatīs why I ask for physical dimensions for both of them.

                              In fact, strong suspicion than almost any 30-40W SS power Transformer pulled from a dead amp (Peavey-Laney-Crate-"mystery brand") will work there, transistors are more "forgiving" than tubes.
                              As long as voltages are +10/-20% and come from same or larger power rating amp, no big deal.

                              If anybody has a full Minx or Envoy schematic, please post it here, guess it will have more than passing resemblance.
                              Juan Manuel Fahey

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