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IBM EGA Card Memory Expansion Boards

ab0tj

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Hi all. One of the projects I have been working on lately is recreating the PCB for the IBM EGA memory expansion board (part number 6480099). I'm going to have board made either way to expand my own system, but I was wondering if there was a need out there and I should get extras? They seem to be hard to find. You'd have to source your own components to solder on the board.
 

maxtherabbit

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Hi all. One of the projects I have been working on lately is recreating the PCB for the IBM EGA memory expansion board (part number 6480099). I'm going to have board made either way to expand my own system, but I was wondering if there was a need out there and I should get extras? They seem to be hard to find. You'd have to source your own components to solder on the board.

man you and I have a lot of overlapping interests, I'd probably want one or at least the file to get my own if you release it

Great Heirophant had expressed interest as well
 

ab0tj

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man you and I have a lot of overlapping interests, I'd probably want one or at least the file to get my own if you release it

Great Heirophant had expressed interest as well

Apparently we do. Luckily enough this one isn't difficult since the schematics are already available. I just had to transcribe it into KiCad :)
I am definitely willing to share the design files when they're done. Economy of scale helps the costs when ordering PCBs so if others are interested it's nice to make one big order.
 

ab0tj

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By the way, if someone has one of these and could provide some measurements (namely overall dimensions, spacing and diameter of the holes, standoff length) that would be helpful. Otherwise I'll figure it out when my EGA card shows up :D
 

modem7

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By the way, if someone has one of these and could provide some measurements (namely overall dimensions, spacing and diameter of the holes, standoff length) that would be helpful. Otherwise I'll figure it out when my EGA card shows up :D
See [here].

Hole diameter is 4 mm.
 

ab0tj

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Got it.

Where in the PDF, it shows "12.70", I measure 13 mm, so close enough there.

However, the two holes in the IBM EGA card are 4 mm diameter.

Thanks for checking on this. Looks like the holes in the expansion card would need to be 4.8mm to support these standoffs, and they would fit in the 4mm holes of the EGA card. I'll keep looking but if I can't find standoffs that are 4mm on both ends, it looks like there's room in the expansion card design to enlarge the holes a bit.
 

modem7

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The photos at [here] show how close the IBM Graphics Memory Expansion Card comes to the adjacent card in an IBM 5170.
Clearly, that is why the IBM Graphics Memory Expansion Card has a protective sheet over its solder side.

(The photo is not of my 5170's normal slot configuration. I normally leave an empty slot next to the IBM EGA card.)
 

ab0tj

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Good news and bad news...

Good news and bad news...

So the good news is... It works. I soldered it together and it required zero rework. Always nice when that happens.
The bad news is there's some fitment issues. The holes for the standoffs had to be drilled out a bit... Not sure yet if that was a design problem or if I just hit the maximum size the board house can drill. Also I think I need a longer pin header to connect to the EGA card, because I have to bend the board in order to plug it in completely if using the standoffs.

Overall not too bad for a prototype!
 

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mikey99

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You might be able to just use a M-F header to extend the pins and get the proper board spacing.
 
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