Amiga B2000 PSU Heart Transplant

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ChewChew

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Here’s my B2000 PSU case fitted with the guts from a 500W ATX PSU.

I’m sure this has been done many times before, but I’m pleased with the results so thought I’d share.

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I used the Amiga PSU PCB as a template to mark up a bit of glass fibre sheet for size and mounting holes. I then lined up the ATX PSU PCB with one of the Amiga PSU mounting holes and marked up the three others on the fibre sheet. M3 brass standoffs were fitted to three of the ATX PCB mounting holes.

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The glass fibre sheet was fixed into the Amiga PSU case using two of the original screws and one M3 brass standoff. This final standoff fixes to the Amiga PSU case and provides the earth to ground connection to the ATX PCB.

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The result is a neat and reversible solution to get my B2000 up and running whilst I try to repair the original PSU. If I cannot repair it, I will at some point add -5V to the ATX PSU which is missing, but not essential right now.

Notes -
I can’t comment on other ATX PCBs, but the one I used had connections to the metal case (earth) at two of the fixing holes. Bottom left and upper right. I made sure the bottom left one was attached to the metal case. But the top right is attached to the glass fibre sheet and not connected on the PCB, so I added a short bit of green wire (you can just make out from the picture) to the ground on the PCB. I could have used a piece of wire with two ring crimps between the fixing screw and the earth stud, but I did not have those to hand.
 
Here's a nice picture to help with understanding the earthing arrangement I described in my previous.

ATX_PSU_PCB.jpg


You’ll see the top left and bottom right fixing holes have an exposed pad designed to make electrical contact with the metal case and remember the metal case is connected to earth.

The bottom right pad ties the secondary (LV) GND to earth which I believe helps prevent earth loops. The top left pad connects the primary (HV) side of the transformer to earth via a pair of capacitors which I believe helps filter out high frequency noise to reduce EMI.

Whatever their purpose is, they both were connected to earth when the PCB was fitted in its original case, so I made sure to do the same when I fitted the PCB to the Amiga PSU case.
 
Really nice and proffessional work. I have two A2000z so it could be very useful for me in the future :)
 
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