Notes on Cleaning and Repairing an Apple II Plus
D Finnigan
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.
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.
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).
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.
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.
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.
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.
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.
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.
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. :-)
--
Mac GUI Vault - A source for retro Apple II and
Macintosh computing.
http://macgui.com/vault/
Michael J. Mahon
> 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."
D Finnigan
> 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... ;-)
>
Yes, but sometimes I just wish that I could get experience with someone
else's equipment, or with equipment for which I had many spares. (Oops,
broke one; go fetch me a spare and we won't do *that* again...)
>> It had a gold power supply
>> with
>> a serial number in the 100k range.
I checked again last night from a photo, and it was actually lower, in the
81k range. I don't have the Apple II here, nor do I have the sheet on which
I wrote the serial numbers, so it's just my memory.
Actually, I've been checking various dates, and they don't seem to line up.
I already said the motherboard date reads as an early 1979, maybe Feb. But
there's a date stamped on the case that looks like Oct 2 1980, and some of
the chips on the motherboard seem to have date codes from 1980. I wonder if
the motherboard is manufactured earlier, then populated with ICs later, and
then finally put in a case.
>
> 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 wonder if spraying WD-40 into the keyswitch would work well.
>
> I recommend doing an unfamiliar disassembly on a large table covered
> with newsprint or something like it, so that errant pieces are easily
> noticed.
Apparently, the dining room table wasn't large enough! I managed to get the
screws separated out so that I could put them back in the right groups
(power supply, motherboard, keyboard, etc.) I just slipped up with those two
space bar thingies. With my luck, they've probably flown off out a window
somewhere. :-/
>
> You were quite lucky--that cable inversion can do some exciting things!
>
So I've heard, and I was worried that I had in fact fried either the drive
or the controller card. In my haste, I even pulled the card out while the
power was still on, (what was my problem?! I probably needed more sleep) but
the Apple just reset.
> 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. ;-)
>
Well, my thought was that maybe the moisture lead to it getting zapped. I
even tried plugging the keyboard cable in the other way around to see if
that was the problem. It wasn't, but it made an interesting pattern on the
screen when I turned the Apple on!
>
> 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.
Something gave me a strong impression that I do not have a Revision 7 board,
and that was the presence of three 16k memory select blocks. I'm guessing
that it's revision 6 or something, because it has the single wire-wrap video
pin, as well as the color-killer transistor. And it also has all of the
chips to the right of the 6502 CPU. The copyright date below the 6502 is
1978. Unfortunately, I can't check the motherboard part number at the
moment, so that will have to wait.
D Finnigan
> goofy CH paddles with 16-pin to DB-9
> adapter,
> the
> goofy CH paddles (so described because they did not have a knob, but
rather
> a 1-axis stick).
>
Sean Fahey was curious to know about these, and other people may be too.
Since I couldn't find any pictures online, and I don't have my own handy, I
made a crude ASCII art from memory:
||
/------------\
|\ ch /|
| \ |---| / |
| \ |---|/ |
| / \ |
| / \ |
|/ ---- \|
| [[[===||} |
| ---- |
\------------/
The general dimension is rectangular, in a portrait style. The button is at
near the top, at the center, and the plastic slopes down on 4 sides around
it. Movement is made by a single-axis joystick that moves only from left to
right. In this diagram, it has been moved all the way to the left. The cable
comes out at the top end of the paddle. It says CH Products either at the
top corner or the bottom corner. I couldn't remember, so I just put it at
the top.
Michael J. Mahon
> Michael J. Mahon wrote:
>
>>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... ;-)
>>
>
>
> Yes, but sometimes I just wish that I could get experience with someone
> else's equipment, or with equipment for which I had many spares. (Oops,
> broke one; go fetch me a spare and we won't do *that* again...)
This is part of the "practice on things that don't matter" rule. ;-)
>>>It had a gold power supply
>>>with
>>>a serial number in the 100k range.
>
>
> I checked again last night from a photo, and it was actually lower, in the
> 81k range. I don't have the Apple II here, nor do I have the sheet on which
> I wrote the serial numbers, so it's just my memory.
>
> Actually, I've been checking various dates, and they don't seem to line up.
> I already said the motherboard date reads as an early 1979, maybe Feb. But
> there's a date stamped on the case that looks like Oct 2 1980, and some of
> the chips on the motherboard seem to have date codes from 1980. I wonder if
> the motherboard is manufactured earlier, then populated with ICs later, and
> then finally put in a case.
Exactly.
The manufacturer procures chips from various sources and in various
quantities, so some stock is older than others. When a board is built,
it will contain the "current" chips in stock, but, of course, none will
be newer than the build date. ;-)
If you inventory the chip dates on a board and find a distribution of
dates, the build date is most likely not long after the latest chip--
unless there are a few chips with significantly later dates than the
rest. In that case, the later chips were probably replacements made
after the build date.
>>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 wonder if spraying WD-40 into the keyswitch would work well.
Dangerous. WD-40 contains ingredients which can cause some plastics
to expand. It is also *not* a contact cleaner nor a de-oxidizer.
Avoid using *any* liquids on keyswitches unless nothing else works,
and then use only electronic contact cleaner/lubricant, and very
sparingly.
Once you spray or wash something into a keyswitch, any non-volatile
components (including dissolved dirt) will stay there forever--unless
you enjoy disassembling keyswitches and manually cleaning them. ;-)
>>I recommend doing an unfamiliar disassembly on a large table covered
>>with newsprint or something like it, so that errant pieces are easily
>>noticed.
>
>
> Apparently, the dining room table wasn't large enough! I managed to get the
> screws separated out so that I could put them back in the right groups
> (power supply, motherboard, keyboard, etc.) I just slipped up with those two
> space bar thingies. With my luck, they've probably flown off out a window
> somewhere. :-/
I'm betting they will turn up--hopefully before the next vacuuming. ;-)
I've sometimes put a handkerchief "pouched" between vacuum cleaner
hose fittings, then vacuumed an area (being careful to hold the "pouch"
upright inside the fittings before turning off the airflow. Careful
opening of the fittings and perusal of the contents of the pouch has
revealed the missing parts (and much else ;-).
It's easier if the missing parts are magnetic...then a sweep with a
strong magnet usually does the trick.
>>You were quite lucky--that cable inversion can do some exciting things!
>>
>
>
> So I've heard, and I was worried that I had in fact fried either the drive
> or the controller card. In my haste, I even pulled the card out while the
> power was still on, (what was my problem?! I probably needed more sleep) but
> the Apple just reset.
You are indeed golden!
>>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. ;-)
>>
>
>
> Well, my thought was that maybe the moisture lead to it getting zapped. I
> even tried plugging the keyboard cable in the other way around to see if
> that was the problem. It wasn't, but it made an interesting pattern on the
> screen when I turned the Apple on!
That's always a possibility, but the thing to do, then, is to wait a
*long* time (2-3 days?) so you're *absolutely sure* that no moisture
remains, and 1) try again--all may be well, or 2) then try replacing
the encoder, since now you can be reasonably sure that any moisture
path that killed the first one won't kill another.
>>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.
>
>
> Something gave me a strong impression that I do not have a Revision 7 board,
> and that was the presence of three 16k memory select blocks. I'm guessing
> that it's revision 6 or something, because it has the single wire-wrap video
> pin, as well as the color-killer transistor. And it also has all of the
> chips to the right of the 6502 CPU. The copyright date below the 6502 is
> 1978. Unfortunately, I can't check the motherboard part number at the
> moment, so that will have to wait.
Bingo.
It is definitely pre-rev 7. You can either use the proto area in the
lower right corner of the board (slots on top) to wire up the enhanced
color burst gating that was pre-installed on the rev 7 board, or you
can try a different color monitor, hoping for one that is less sensitive
to color burst leakage.
Or you can use a monochrome monitor wired directly to the video output
jack and ignore the color monitor when using text modes. (That was my
standard mode of operation).
D Finnigan
>>
>> Something gave me a strong impression that I do not have a Revision 7
>> board,
>> and that was the presence of three 16k memory select blocks. I'm guessing
>> that it's revision 6 or something, because it has the single wire-wrap
>> video
>> pin, as well as the color-killer transistor. And it also has all of the
>> chips to the right of the 6502 CPU. The copyright date below the 6502 is
>> 1978. Unfortunately, I can't check the motherboard part number at the
>> moment, so that will have to wait.
>
> Bingo.
>
> It is definitely pre-rev 7. You can either use the proto area in the
> lower right corner of the board (slots on top) to wire up the enhanced
> color burst gating that was pre-installed on the rev 7 board,
I did more reading, and it looks like there wasn't a rev 6, but my board may
well be a revision 3. The description matched mine: 16k memory select blocks
that are not soldered down. Mine were removable.
Apple II/IIplus production dates by spacealbum:
Rev. 3 board 820-0001-03 silkscreened under the CPU, CPU has to be
removed to see it, handwritten numbers on the boards are production
dates, used from 78?? until 7930 (=30th week of 1979), memory select
blocks can be removed, lowest Apple serial number I have seen is
A2S1-14282, highest A2S1-31907, maybe very early IIplus models used
this board as well.
My board looks like this one:
http://i158.photobucket.com/albums/t118/bradandjennifer_2007/80251-1.jpg
Ack, I need to get back to that Apple so I can say for sure what it is.
Unfortunately, it's been put away (there's no room for it here; put it
away!).
> or you
> can try a different color monitor, hoping for one that is less sensitive
> to color burst leakage.
>
> Or you can use a monochrome monitor wired directly to the video output
> jack and ignore the color monitor when using text modes. (That was my
> standard mode of operation).
>
I'm still using the color television set in the living room that's about 10
years old. I haven't got a dedicated monitor yet. :-(
Linards Ticmanis
> Once you spray or wash something into a keyswitch, any non-volatile
> components (including dissolved dirt) will stay there forever--unless
> you enjoy disassembling keyswitches and manually cleaning them. ;-)
Which isn't all that hard with the black-and-gray switch type Apple or
their keyboard supplier seem to have used most commonly. Just unsolder
the problematic switch, remove the caps of the surrounding keys, press
the snap-in thingies towards the center and carefully pull it out
(upwards). Then it's easy to take it apart, it's all just snapped
together, no screws, no glues. As long as you remember where each part
goes and take care that the spring doesn't propel itself away, you can
then get a small screwdriver or something similar between the two actual
contacts and carefully scratch a bit, then reverse the whole process.
That way I recently revived some switches which simply weren't willing
to work right - I'd get either no character on screen or several at
once, no matter how many hundreds of times I had pressed the key. Turns
out the culprit was a bit of verdigris which had formed on the contacts,
probably too much of it to be removed without disassembly.
> It is definitely pre-rev 7. You can either use the proto area in the
> lower right corner of the board (slots on top) to wire up the enhanced
> color burst gating that was pre-installed on the rev 7 board, or you
> can try a different color monitor, hoping for one that is less sensitive
> to color burst leakage.
Actually the reliable interim fix didn't happen until Rev. 8 or 9
according to Jim Sather, and the final fix came with the RFI board. I
had to do the fix on my Rev. 7 board to get it to play with a particular
TV set, putting in an extra 74LS04 if I remember correctly. Which I then
also used to get rid of the infamous "orange line" at the left edge of
the screen.
--
Linards Ticmanis
Michael J. Mahon
> On 04/25/2011 11:22 PM, Michael J. Mahon wrote:
>
>
>>Once you spray or wash something into a keyswitch, any non-volatile
>>components (including dissolved dirt) will stay there forever--unless
>>you enjoy disassembling keyswitches and manually cleaning them. ;-)
>
>
> Which isn't all that hard with the black-and-gray switch type Apple or
> their keyboard supplier seem to have used most commonly. Just unsolder
> the problematic switch, remove the caps of the surrounding keys, press
> the snap-in thingies towards the center and carefully pull it out
> (upwards). Then it's easy to take it apart, it's all just snapped
> together, no screws, no glues.
Each switch is not too bad, but a few dozen is a real grind. ;-)
> As long as you remember where each part
> goes and take care that the spring doesn't propel itself away, you can
> then get a small screwdriver or something similar between the two actual
> contacts and carefully scratch a bit, then reverse the whole process.
> That way I recently revived some switches which simply weren't willing
> to work right - I'd get either no character on screen or several at
> once, no matter how many hundreds of times I had pressed the key. Turns
> out the culprit was a bit of verdigris which had formed on the contacts,
> probably too much of it to be removed without disassembly.
This kind of "direct intervention" is certainly effective, but there
is a danger that it will accelerate future failures.
The switch contacts are typically phosphor bronze (for springiness)
plated with silver (for low contact resistance) and sometimes "flashed"
with a thin plating of rhodium or other corrosion-resistant metal. The
contacts are then lubricated with a dry, non-corroding lubricant for
longer life.
Scratching or sanding the contacts removes the plating(s), exposing
the base contact metal. This will certainly work, especially if the
switch is used regularly so that the wiping action of the contacts keeps
them oxide-free. But it also makes the contact more vulnerable to
oxidation.
If necessary, contacts should be burnished lightly with a silver
polishing cloth or a thin wood shaving. The mild abrasion will remove
tarnish from the silver plating while leaving it (hopefully) intact.
In the case of your green-corroded contact, the silver was clearly
already breached, since the green coloration indicates the presence
of copper salts from the bronze. This is usually the result of some
prolonged exposure to moisture. Hopefully, it indicates that only one
keyswitch was affected, but maybe not.
A keyboard with several corroded switch contacts is a pretty good sign
that a new keyboard is in your future.
D Finnigan
>
>> It is definitely pre-rev 7. You can either use the proto area in the
>> lower right corner of the board (slots on top) to wire up the enhanced
>> color burst gating that was pre-installed on the rev 7 board, or you
>> can try a different color monitor, hoping for one that is less sensitive
>> to color burst leakage.
>
> Actually the reliable interim fix didn't happen until Rev. 8 or 9
> according to Jim Sather, and the final fix came with the RFI board. I
> had to do the fix on my Rev. 7 board to get it to play with a particular
> TV set, putting in an extra 74LS04 if I remember correctly. Which I then
> also used to get rid of the infamous "orange line" at the left edge of
> the screen.
>
I finally got the II Plus back last weekend, and I pulled out the 6502 to
check. It's definitely a revision 3 board.
820-0001-03
Old-school, a little out of date, but who cares? That's the whole point of
the Apple II. If it's easy, then you're doing it wrong. :-)
--
]DF$