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Thread: IBM 5150 Model A - 120 to 220V PSU Conversion

  1. #1

    Default IBM 5150 Model A - 120 to 220V PSU Conversion

    Heya folks

    I live in the UK and I've got a 5150 Model A which has a black 120V PSU. I am quite keen to get it running from 220V without a step-down transformer.

    I've spent the last few days studying the schematic and can see that is very likely possible. There very clearly is not any switch, jumper or even a set of fitting options to convert it but theoretically it looks possible.

    Does anyone have even a photograph of the insides of the black 63W 220V supply? Did one even exist?

  2. #2
    Join Date
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    Quote Originally Posted by inaxeon View Post
    Heya folks
    "Heya" back. Welcome to these forums.

    Quote Originally Posted by inaxeon View Post
    Did one even exist?
    Mine is pictured at [here].

    And I am pretty sure that a forum member here in Australia acquired one recently via eBay.

    Quote Originally Posted by inaxeon View Post
    Does anyone have even a photograph of the insides of the black 63W 220V supply?
    I have added your request to my to-do-list.

  3. #3

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    Quote Originally Posted by modem7 View Post
    "Heya" back. Welcome to these forums.


    Mine is pictured at [here].

    And I am pretty sure that a forum member here in Australia acquired one recently via eBay.


    I have added your request to my to-do-list.

    Thanks for the response.

    From looking at the schematic it is clear that the 120V edition was designed with 230V operation in mind, and it seems possible that there is a variant of it out there which accepts 230V input. Quite possible that you may have one there. Question is what exactly are the differences. I suspect not very much...

    Would definitely appreciate photos. If you are going to go to the hassle, start with the top of the PCB. I had quite a job removing the PCB from mine, and there is little point in you going to that length if it is fundamentally a different design!

    Thanks!

  4. #4

    Default

    Thanks for the response

    From looking at the schematic I can see that the 120V edition was designed with 230V operation in mind. It seems quite possible that there is a variant out there which accepts 230V input. Quite possible, that is exactly what you have there. Question is what exactly are the differences, I suspect not much...

    If you are going to take pictures - start with the inside "top" shot. I had quite a job getting the PCB out of mine. No point in you expending that effort if it is a fundamentally different design!

    Thanks

  5. #5

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    Quote Originally Posted by modem7 View Post
    "Heya" back. Welcome to these forums.


    Mine is pictured at [here].
    Apologies if I'm hijacking the thread, but that link makes for some interesting reading regarding my 5150. Mine seems to identify as an early 5150 (2 screws at back, lack of 'B' in circle, 16KB-64KB motherboard, black wide brackets on the expansion cards) but then there are signs it came a little bit after (silver PSU, second BIOS revision "5700671", TM100-2A floppy drives, plastic speaker holder). Interesting to see the little changes they made along the way.
    AtariPC.net
    Atari PC | IBM Compatible Series

  6. #6

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    Quote Originally Posted by inaxeon View Post
    I am quite keen to get it running from 220V without a step-down transformer.
    It might be your lucky day. I had the same problem, a messy step-down transformer and knowing I (or someone) would eventually forget and blow it up.

    After a couple of years thinking about it and studying the schematic, I designed a modification and updated my two (chrome) 120V 63.5W units a few months ago, and they now work fine at 230-240V. I've also fully documented the process including the engineering.

    Post a photo of the inside so that I can see if it's the same PCB. You may have an AC fan which obviously would need to be replaced.

    Yes, you are right that the primary DC portion of the circuit is wired as a voltage doubler and as such could run at 230 V under full wave rectification, but not the support components. I've never seen a schematic for the 240V unit so have no idea how that works, or even if it's the same concept.
    Attached Images Attached Images
    Last edited by paul; January 10th, 2017 at 11:01 AM.

  7. #7
    Join Date
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    Quote Originally Posted by Flamin Joe View Post
    Apologies if I'm hijacking the thread, but that link makes for some interesting reading regarding my 5150.
    Then you should take a look at the remaining 5150 information at that web site: http://minuszerodegrees.net

  8. #8

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    Quote Originally Posted by paul View Post
    I've also fully documented the process including the engineering.
    Would certainly be good if you could share that.

    It's a work in progress, but I have attached my proposed changes so far. Perhaps you could compare that to your changes?

    psu.jpg

  9. #9
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    Sevenoaks, Kent, United Kingdom
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    Were is the schematic ? I will take a look.

  10. #10

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    Quote Originally Posted by Clint View Post
    Were is the schematic ? I will take a look.
    I have combined the several page PDF commonly floating around into a single image - here

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