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WIP - exxos 4MB RAM upgrade on MEGA ST1

Posted: Fri Jul 05, 2019 9:39 pm
by Marsupilami
I'm trying to upgrade my MEGA 1 with the great Exxos KIT #35.
It's my first attempt so i may have made some mistakes :?

First the kit out of the box :
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Then reading the links provided may help. Yes, well...if you know what is the part number of the components like shifter, glue etc...If you don't have any idea, search the part numbers with google. I found mine here.
The Mega 1 board
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Before soldering :
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Soldered (part 1)
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Once soldered, the pins in the center needs to be trimmed (with cutting pliers) otherwise the 40 pin socket won't fit.
Notice the little component soldered to the pin 40 of the "shifter" (in my case CO70713)
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Remove this component from the shifter. We'll need to solder it again to the kit later. Then remove the shifter.
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Solder the 40 pins socket to the adapter then put the shifter on it.
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Now solder back the [hum...whatever] to the pin 40 of the kit once plugged into the motherboard.
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Now you need to find the MMU, for me it was the "C100109". Notice that there is no number "26" or else written on the (or at least on my) my kit so you'll need a bit of imagination to find the good position :)
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Gently push it into position.
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Now add the cable, take care, it's not very long but it fits :
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I hope i did everything the right way. If someone can confirm.. :)

But now...I'm stuck. I don't find the R59 and i don't know if i need to lift others R#...ie what am i supposed to do ?
If i don't find the good resistances to lift up, i will remove the existing RAM. But it's unclear for me. I mean just removing the 8 RAM chip is enough ? If i remove the 8 (only 8 so i suppose it's 8x128k) do i still have to remove anything else ?
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Thanks for your help :)

Re: WIP - exxos 4MB RAM upgrade on MEGA ST1

Posted: Fri Jul 05, 2019 9:45 pm
by exxos
Have you read the install page ? http://www.exxoshost.co.uk/atari/last/4MBMMU/index.htm

MEGA ST resistors are listed on that page...

Re: WIP - exxos 4MB RAM upgrade on MEGA ST1

Posted: Fri Jul 05, 2019 10:18 pm
by Marsupilami
exxos wrote:
Fri Jul 05, 2019 9:45 pm
Have you read the install page ? http://www.exxoshost.co.uk/atari/last/4MBMMU/index.htm

MEGA ST resistors are listed on that page...
Yes i did and it was really helpfull. But since the title is "OLD RAM ISOLATION MEGA ST" and the MB part # is different, i don't want to do any mistakes :)

So just to be sure, should i do like that (even if the MB rev # is different):
Image
or
Remove the 8 RAM chips.

Re: WIP - exxos 4MB RAM upgrade on MEGA ST1

Posted: Fri Jul 05, 2019 10:24 pm
by exxos
Marsupilami wrote:
Fri Jul 05, 2019 10:18 pm
But since the title is "OLD RAM ISOLATION MEGA ST" and the MB part # is different, i don't want to do any mistakes :)
The version of the board doesn't really matter, or the resistor numbers really.. its the location on the board which is the main thing.. so you can follow that image for initial testing.. once working, I would cut out the old RAM.

Re: WIP - exxos 4MB RAM upgrade on MEGA ST1

Posted: Fri Jul 05, 2019 10:46 pm
by Marsupilami
Ok thanks a lot, i'll try tomorrow. Once the old RAM removed, should the resistors be kept with the 2 added wires or removed or be soldered back in initial state ?