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IIgs memory expansion board HELP! 670-0025


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I am hitting my head against a wall and need some help. I have been dealing with a IIGs memory expansion board model 670-0025 for over a year and a half and enough is enough. I need help. I cant find a schematic for this board.

 

I got the boad and it was not working, It was a bit crusty but but nothing otherwise of note. I determined to TTL logic chips failed and replaced them. But since the solder was so old and crusty desoldering was a problem and a few traces lifted and broke. I bodge wire fixed 3 bad traces but here is the problem. The card "works" but only up to 512KB, it WILL NOT detect the other 512KB of chips in the card. Yes those chips are 100% working I already checked that. I have other working boards of the same model and I have been trying to continuity check every connection but its intolerable. I need a schematic and some advice as to what possible line is broke to inhibit the other (lower) 512KB of RAM from being seen.

 

Please help, I want to be done with this card!!!

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See this is what bothers me. No one chiming in means there ARE NO schematics out there...  It is beyond stupid and promotes a throw away culture if things aren't given a chance to be repaired. Its infuriating. I have already ran into this problem with Apple Color composite monitors.

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I buy alot of old apple equipment. In various stages of neglect. I like the repairing. And truthfully id say of all the many Apple branded ram IIgs cards I have come across, maybe only 10% had problems. Its usually the TTL logic. I think I have only seen bad ram chips twice maybe 3 times; and thats no problem as they are all socked (yes the first 256KB is soldered on but I don't think I have ever had a card with the first 256KB being faulty.

 

I will say a MAX of 1MB in 1986 or 1987 whenever the card was made was really not forward thinking at all. Why wouldn't they have set a 2MB or 4MB limit? Or released a better card.... The nice thing is the RAM chips can be found easily and relatively cheaply, I have an AE RAM works card that only maxed out at 6MB but the chips alone to populate that would be well over $100.00 as they are not all that abundant.

 

Keep in mind, I do this as a hobby, This is not for my main IIgs. This is for one of the many in my collection I am fixing up. I already own a GGlabs 8MB module I bought a couple years back. But I like fixing these cards when I can. If I give this machine to someone who only wants to play some basic games or use it in apple II 8 bit mode, they don't need much RAM at all and its period correct which some purists like.

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