6 Jan
2013
6 Jan
'13
3:54 p.m.
On Sun, 6 Jan 2013, Win Heagy wrote:
A quick update on my Apple III. I used the BNK, ADR
and Exp/Got info from
the Apple III RAM test to narrow down the bad RAM chip. I replaced it with
one from an Apple II and it worked. The RAM test completes successfully,
but it does do one odd thing shown in this pic...
http://i.imgur.com/VP98h.jpg
Row 7 gets dashes across it during the second pass and all subsequent
passes. The test, however, continues normally. I ran it over 10 passes
with no problems. Any ideas what the dashes mean?
On the downside, my III still doesn't boot. It does pretty much what it did
before. WIth an SOS disk in the drive, it spins for about 3 seconds, then
nothing. The demo disk does the same thing. The III+ diagnostic disk that
used to boot, doesn't boot anymore and fails with an IO error message.
This makes me think again that there may be a floppy drive issue. Is the
drive calibration method that was mentioned previously the one that is
outlined in the Sun Remarketing Do It Yourself Guide for adjusting Apple
III drive speed...that uses a 60 Hz light source? If so, I guess that's my
next task to try to revive this machine.
Almost all the A3 drives that have come my way were malfunctioning. Best
bet is to disassemble them and carefully clean and lube. First, use some
canned air to blow out all the dust bunnies. The original grease used on
the head assembly rails and the spiral-cut plastic stepper wheel
solidifies over the years. I usually use a tiny bit of WD-40 on a swab to
remove the old lubricant, then a bit of Tri-Flow to replace it.
A speed adjustment may very well be needed, but another problem area is
the two trimpots on the top of the drive circuit board. They tend to grow
oxide and become intermittant. Mark the position of the pots with a
felt-tipped pen, then wiggle them with a screwdriver until the little gob
of locking compound breaks. Squirt a small amount of non-residue control
cleaner in the side and work them through their rotation a few times.
Reset to the marked position. You can lock them in place again with a dab
of nail polish, but don't do this until you know that things are working
again! Reseat all the chips on the board and check closely for "black pin"
syndrome. For some reason, the chips in the disk drives seem more prone
to this (more exposure to humidity?) If you see this, pull all of them
and take a contact cleaning tool to the legs.
Finally, take a swab and carefully clean the head with isopropyl alcohol.
I've successfully repaired four or five drives in this manner.
Steve
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