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Re: Notes on Cleaning and Repairing an Apple II Plus

D Finnigan wrote:

I obtained an Apple II Plus yesterday. As is typical of me, a few hours
after I plugged it in and verified it to be working, I managed to break it.
Here are my notes from cleaning and repairing it, for future benefit. Ah,
experience. What a teacher.


Yep.  Good judgement comes from experience, and experience comes
from poor judgement...  ;-)


What arrived was an early-model Apple II Plus, with a motherboard date of
7905 and 5-digit serial number (90k range). It had a gold power supply with
a serial number in the 100k range. Inside was a Language card, Disk II
controller, and Sup-R-Mod II. Also included was 1 Disk II drive (rainbow
cable, serial number in 100k range), goofy CH paddles with 16-pin to DB-9
adapter, some diskettes, 13-sector PROMs, and the usual manuals that one
gets with a II Plus.

When I first plugged it in and turned it on, I noticed that the color killer
circuit was a bit unstable. The text would be color-free for about 10-15
seconds, then would get fringes for awhile, then alternate back. All of the
keys on the keyboard were working except for the B key. It turned out to be
a poor electrical connection. After I pressed the key for about 20-30 times
in a row, with a bit of extra force than usual, the B started working.


Right--your repeated operation of the keyswitch mechanically abraded the
oxides on the surface of the switch contacts.

The best way to keep a keyboard *electrically* clean is to use it
regularly to prevent oxidation from building up.


I also confirmed that the Disk II drive was working, and managed to boot up
one of the disks that was included, and played the Bug Attack game using the
goofy CH paddles (so described because they did not have a knob, but rather
a 1-axis stick).

Then I decided to strip it down and take a bath (the Apple II Plus, that is,
not me).


Here is where you made your mistake...

"Pretty" (externally clean) is not *actually* clean in the places that
matter (like at the contacts of keyswitches or between traces and the
DIP socket traces that straddle them).

Soft brushes, vacuums, and even compressed air for cleaning have
relatively few failure modes (but watch out for loose chips when
using compressed air!).  Cleaning with any liquid has serious risks.

Liquids mobilize dirt, deposits, and corrosion, so that it can move
into hard-to-get-at invisible places where it can cause trouble.  And
any ionic liquid, like anything water-based, will ionize any soluble
residues on the board, forming a conductive path.  Not good, but the
path will generally deionize when all the water is evaporated...

But you can't rush the drying!  There are myriad tiny crevices which
are wet by capillary action, and they can take some time to dry in
warm conditions.  I'd always allow *at least* 24 hours to dry before
applying any power to a board.  Applying power while any trace of
moisture remains is potentially harmful to your board.


Disassembly was fairly straight-forward. I removed the top case, power
supply, and logic board. When washing the case, I noticed that small black
pinholes appeared in the resin. I wonder if they are caused by bubbles. I
decided to not scrub so vigorously.

I board washed the logic board and pressed down on the chips. Most all of
them were loose. I did the usual technique of flinging water off the board,
then placed it on the gas heater to dry out.

Washing the keyboard was a bit more eventful. I pried off all of the keycaps
and placed them in the sink with warm water (over 100 degrees F, I'd
imagine) and soap. I managed to lose the two plastic supports which go on
either end of the space bar. They probably flew off somewhere, and I'll
spend some more time looking before I give up. This keyboard was the newer
style with flat power light and two-part encoder/switch board assembly. I
discovered that there is a switch on the encoder board which I later learned
is for controlling the Reset key behavior.

Next I put the enter keyswitch board in the sink to wash off the cigarette
tar and residue. Yes, the whole thing smelt faintly of vintage cigarette
smoke, but one had to get one's nose down into it to tell. I flung the water
off of the keyboard and placed it on the heater to dry too (I had taken the
motherboard off earlier). This is probably about when the plastic space bar
supports fell off.


I recommend doing an unfamiliar disassembly on a large table covered
with newsprint or something like it, so that errant pieces are easily
noticed.  If they dislodge themselves before you have a chance to see
how they are installed, reassembly becomes guesswork.


The last major thing to clean was the Disk II drive. It too smelt of
cigarette smoke, even inside. I opened the case to wipe out some of the dust
on the white metal "floor" and lubricate the rods on which the head assembly
traveled. In the process, I unplugged the analog board to remove it.

Finally, I reassembled everything, and put all of the keycaps back on. The
entire cleaning took about 2 hours, I'd estimate. I waited an additional
half hour for the last bits of water to dry up. I then plugged back in all
of the cards, the disk drive, and connected the II Plus the TV. When I
turned the machine on, nothing happened. I heard the usual rapid clicking
from the power supply that is indicative of an electrical problem.

I removed the Sup-R-Mod, Language Card, and Disk II controller. When I
powered the Apple on again, it booted successfully. There was a short
circuit somewhere, I supposed. Through process of elimination (I'll skip the
details), I determined that the Disk II drive was at fault. I opened it up,
and sure enough, I had plugged the rainbow-colored data cable in upside down
on the analog board. I fixed it, and the Apple II powered on successfully,
and the Autostart ROM accessed the disk drive. It booted a disk.


You were quite lucky--that cable inversion can do some exciting things!


However, there was another problem. The keyboard first was acting as though
I was holding down the 9 and REPT keys, though I was not. When I reconnected
the disk drive and powered up, random characters were output on the screen,
and sometimes pressing one key character would output a different character.
Some of the keys didn't work at all. Only the Reset key behaved normally.


Residual moisture in the keyswitches...  Be patient!


I consulted the repair documentation that I provided online a few years ago,
and it said that the likely cause was a bad encoder. Well, I disassembled
the keyboard again, and checked all of the connections. I powered down,
waited an hour, and tried again. Still nothing, same results.


If you've just washed the keyboard, the encoder is *not* the most
likely problem (as you discovered).

Nine times out of ten, the problem is with something you just did,
not something else.  ;-)


Finally, as a last ditch effort, I tried a technique which has worked for me
in the past: leave it on for a long time. At 10 PM last evening, I powered
on the Apple II Plus, and went to bed. This morning, at 10 AM, I turned on
the TV and tested the keyboard. It was working just OK! The only key that
does not work is the right shift key. It may simply need some additional
exercise, and it may not have worked when I originally received the Apple.
In any case, it's not such a big deal.


Yes, that key will almost certainly be revived by exercise.


However, I am curious as to what was wrong with the keyboard yesterday. My
first thought was that perhaps there was still a little droplet of water
somewhere making a short or wrong connection.


Bingo!


In addition, the color killer circuit is now working properly, and I have
not had the text occasionally shift between fringe/fringeless modes. I also
learned that you cannot connect the 4 pin header of the Sup-R-Mod to the
output of a Videx 80-column card and get the TV to display 80-column video
that way. Finally, I think that the placement of the Reset key is
hilariously idiotic, and so I have left the switch in the "daredevil mode,"
and will do so until I accidentally hit Reset and get roasted. :-)


Early ][+ main boards did not have sufficient isolation of the color
burst, so enough of it leaked through to trigger sensitive monitors to
go into color mode.

Later revisions (7 and later?) had a mod which fixed this leakage.
So if you have a pre-rev 7 (?) board, the over-eager switching to color
mode is authentic.

In general, "If it ain't broke, don't fix it." is good advice.

Cleaning old electronic gear is seldom helpful to its proper function,
and frequently a risk to its health.

Cleaning a case is safe and cosmetic, but cleaning a board must be
undertaken with care.  Some components are sensitive to moisture
but are not sealed--like trimmer capacitors (the color burst phase
adjustment on the ][ and ][+).  Connectors can also develop problems
when exposed to moisture--particularly if it persists (that's the
actual cause of most visible corrosion).  Every contact of two different
metals or alloys becomes a shorted battery when it is moistened with an
electrolyte--which is what dirty water is.

-michael

NadaNet 3.1 for Apple II parallel computing!
Home page:  http://home.comcast.net/~mjmahon/

"The wastebasket is our most important design
tool--and it's seriously underused."