Q: Starting a Mac II

Hi, Dennis -

It's your power supply.  The usual suspects are the electrolytic capacitors inside that go bad (by drying up and/or expanding/leaking) and prevent it from working any more.  Rebuilding the one you have or sourcing a rebuilt one will get you on the road to recovery.  The soft-start (power key on the keyboard) in particular needs a healthy power supply to get going.

Well, you can't buy the off the shelf any more, of course.  You could watch big auction sites - even a whole machine might be an economical replacement.  There's also the Low End Mac swap site as a possibility:

http://lowendmac.com/lists/swap.html

There are also fora dedicated specifically to the Mac II and friends - like this one:

http://68kmla.org/forums/viewforum.php?f=8

Dennis,

Check for capacitor leaks.  Next, more than anything else, contacts need to be cleaned and restored.  We disassemble everything and reinsert every card and RAM stick, etc..

Test the power supply separate from the machine.  On a PC power supply, the green lead is the motherboard relay power lead.  On a PC power supply, if you take a paper clip and jump from the green to the black wire beside it you will have power turn on in the power supply.  I will have to dig up some old files to refresh my memory on what the Mac II wire color is.  It would be too easy if it was the same as a PC.  Then again, we are glad that the Mac was not like a PC back then.

Ji~m

I figured the battery was dead, so I replaced it,

I think that Mac or the IIfx had TWO of those little batteries. Check under the drive shelf, I think they are mounted at 90 degrees to each other.

http://macgurus.com/products/motherboards/mbmacII.php

Grant,

Reading your macgurus link made me wonder, what was the modification that allowed 64meg of RAM on the Mac II?  MacGurus indicate that only 8 meg is achievable in an unmodified machine.  I know that it was advertised as an 64meg machine and that is how FoxPro configured the Mac II to test drive their database in a RAM drive.

Jim

Apple did not ship it that way because there was a "test mode" in some of the chips of that day. If you attempted to access addresses that were not present on the chips, it went into test mode and cycled through all its addresses, never to return.

If my recollection is correct, updated memory modules had a one-chip add-on that made sure the pattern than invoked test mode would get intercepted, not passed to the chips (and keeping them from entering test mode and becoming useless).

I bought and still have four HUGE modules for (I think) the IIfx that have literally four rows of chips each. I am not sure whether they have the "fix" or whether they were built with chips that did not do test mode. They are so big will only fit in a case the size of a Mac II or IIfx, with its enormous amount of headroom over the memory modules.