Mac Forum / General / Hardware / October 2007

But that could mean anything.  You aren't very descriptive.  I seem to recall
that if memory is bad, you will see some sort of number underneat the sad
Mac to indicate the problem.  If there's no number, I suspect things are
in good enough shape that there may be no problem.

Note the Mac Plus would display a sad Mac if you kept the mouse button
pressed down while booting (I had something on top of the mouse).  

You also get a sad Mac if there's no bootable OS on the system (or
to that effect).  There's no hard drive in there, if you don't have
a floppy with the OS in the drive, it will display a sad Mac.  Note
also that it's a pretty old unit, and the drive may be so gunked up
(dried grease or whatever) that the drive can't work to read the
floppy.

The fact that you lack a mouse or keyboard may be the issue, I can't
say I ever tried to start a Mac Plus without either, since you can't
do anything without them, the sad Mac may be a result of them not
being there.

Make sure there's an even number of RAM ICs.

I had a 512KE, and it was like a 128 board.  There was a little daughter
board plugged into a header near the RAM, and of course the RAM were
256K rather than the 64K in the 128 Mac.  It was basically the same
setup as what one had to do to expand the Mac 128 to a Fat Mac.

Connectors mean absolutely nothing.  I've never seen anything to indicate
the keyboard matched anything else.  The Mac Plus keyboard will work on it,
it's the same thing.  It's a standard Mac keyboard until they switched
over to the ADB bus, which means it didn't last that long.  I can't
remember if the SE had an ADB bus or not.

The mouse is easier.  It's basically the raw information from the inside
of the mouse.  (There are two slotted wheels, one for up/down the other
for left right, and each has an optocoupler straddling the wheel.  The
mouse ball moves the slotted wheel, and thus pulses are generated off
the optocoupler.  Depending on the up/down or left/right, one optocoupler
issues the signal before the other.  Thus direction is determined by
seeing which optocoupler goes high first.) The signals are buffered
with schmitt triggers, but the four signals are directly brought to
the Mac, along with the button press (and ground and five volts to
the mouse).  Hence, one can open up any mouse, grab the signal, buffer
it, and send it to the Mac.  After all, any mouse has the basic circuitry,
it just has extra to put that information into the serial signal needed
by the bus it connects to.

  Michael

 I used to repair them old Macs back in the 80's and 90's.  Started
at an Apple dealer in '82.  So well before the Mac even came out.
Sounds like someone remove a RAM chip and pulled a couple of traces
with it.  That's why there are the extra wires, to attempt to repair
the traces they pulled.  Yes, you need a chip there, but if the traces
are not connected, the chip won't do any good.

 The original 128K machines could be upgraded by replacing the 16 RAM
chips, and there was s small circuit board that soldered into the 7
holes at the end of the processor.  That was to add addressing to the
new chips.  The later 128K board just needed the jumper, trace cut,
etc...  I did maybe a hundred of them upgrades.

 The MacRescue was my favorite memory piggyback board.  Went up to 6
MB, although only 4 would be recognized by the OS. Dove was another
popular one, but I didn't like it. I used to solder sockets to the
tops of the piggybacked chips to get a better connection.  There was
also SCSI upgrades by several manufacturers, and even some processor
speedup chips I used to sell.  Only to 16 Mhz, but back then, it was
fast...  I want to say the MacRescue added memory and a SCSI port at
the same time.  The Rescue used SIMMs, the Dove had a bunch of 256M
chips on it.  Up to 2MB on the original Dove board.

 I used to add a fan into the back of the 128k - Plus machines.  I
cut a 3" hole or so, and put a 220V fan and filter on the back.  Ran
at 110v, but ran very quiet at that voltage.  Made lots of money for a
number of years servicing them machines.

Raymond