happymacunhappymac
Well-known member
Hello,
I posted this in the Lounge yesterday but today realized this is probably a much better location. I apologize for duplicate posting.
I've got a Mac II that I'm having trouble with. It was working fine when I put it in storage in about 1990. I recently had it re-capped and had new batteries installed. I also had all the plastic simm sockets replaced with ones with metal clips. The power supply has been re-capped and tested. I've probably got $500 in it at this point.
The machine seems to boot fine, but nubus cards do not work. That means there is no video. I'm no expert, but I think that makes the computer kind of hard to use.
I've sent it to a really competent troubleshooter. This is what he had to say:
"
I think I've made some progress, but hit another roadblock.
I've been comparing the signals on the Nubus slots to my Mac II cx. On the IIcx (with the video card installed) there's activity on all 32 address/data lines as you would expect. On yours, there's absolutely no activity while the computer is running. This tells me it's not detecting the video card.
Just after reset on the IIcx, there's a burst of data on all 32 address/data lines, even with no video card installed. I assume this is when it's polling the bus to see if there are any installed cards.
On yours, I see the same thing, except on AD21, 21,22, and 23. Those are just flat line. This seems very suspicious, but not certain without another identical board to compare to.
I've ruled out the chips that drive the address/data lines by swapping the suspect ones into other locations. The next step up the line gets more complicated.
The schematic I have is for the board 820-0228-A, which is a revised motherboard. Your Mac II has 820-0163-03. Unfortunately, the circuit that drives the Nubus slots is very different.
It looks like I'll need the correct schematic to make any more progress. I haven't found a schematic for this board. Even with one, there's a high likelihood I'll run into a custom Apple chip that I can't conclusively test, or find a replacement for.
"
I'm wondering if anyone out there knows of schematics for the newer version of the II, or if anyone has any tips or suggestions.
Thanks in advance for any leads.
Signed,
Sad Mac Owner
I posted this in the Lounge yesterday but today realized this is probably a much better location. I apologize for duplicate posting.
I've got a Mac II that I'm having trouble with. It was working fine when I put it in storage in about 1990. I recently had it re-capped and had new batteries installed. I also had all the plastic simm sockets replaced with ones with metal clips. The power supply has been re-capped and tested. I've probably got $500 in it at this point.
The machine seems to boot fine, but nubus cards do not work. That means there is no video. I'm no expert, but I think that makes the computer kind of hard to use.
I've sent it to a really competent troubleshooter. This is what he had to say:
"
I think I've made some progress, but hit another roadblock.
I've been comparing the signals on the Nubus slots to my Mac II cx. On the IIcx (with the video card installed) there's activity on all 32 address/data lines as you would expect. On yours, there's absolutely no activity while the computer is running. This tells me it's not detecting the video card.
Just after reset on the IIcx, there's a burst of data on all 32 address/data lines, even with no video card installed. I assume this is when it's polling the bus to see if there are any installed cards.
On yours, I see the same thing, except on AD21, 21,22, and 23. Those are just flat line. This seems very suspicious, but not certain without another identical board to compare to.
I've ruled out the chips that drive the address/data lines by swapping the suspect ones into other locations. The next step up the line gets more complicated.
The schematic I have is for the board 820-0228-A, which is a revised motherboard. Your Mac II has 820-0163-03. Unfortunately, the circuit that drives the Nubus slots is very different.
It looks like I'll need the correct schematic to make any more progress. I haven't found a schematic for this board. Even with one, there's a high likelihood I'll run into a custom Apple chip that I can't conclusively test, or find a replacement for.
"
I'm wondering if anyone out there knows of schematics for the newer version of the II, or if anyone has any tips or suggestions.
Thanks in advance for any leads.
Signed,
Sad Mac Owner