Apple II CPU Hardware and Hardware Projects

Csa2 FAQs-on-Ground file: Csa2HDWHACK.txt  rev012

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 1997 - 1999.

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 001- What's a good hardware project book for the Apple IIe?
 002- How can I use a thermistor to read temperature on my A2?
 003- Will a prototyping Slot Board fit all Apple II's with Slots?
 004- What is the pin-out for the Apple II series Slots? 
 005- I've been getting Fatal System Error 0911. Is there a fix?
 006- Why does my GS Control Panel keep resetting to the defaults? 
 007- How do I replace my GS "BatRAM" battery?
 008- Is there a program to record/restore Control Panel settings?
 009- How I can safely clean out dust from my Apple II?
 010- How can I safely remove oxidation from IC pins? 
 011- After smoke came from my GS the KB doesn't work. What's wrong?
 012- What is the mini circuit board near the front of my GS for?
 013- How do I add RAM & set jumpers on the IIgs 1MB Memory Card?
 014- How can I move my IIgs to a PC tower case?
 015- How can I convert a IIgs into a portable IIgs?
 016- Where can I get Robot kits to use with my Apple II?
 017- Where can I get the chips to expand memory on my AE GS-RAM III?
 018- What is a TrackStar? Does it need special software?
 019- Could someone please post a resistor color code chart?
 020- What advantages does the ROM 3 GS offer vs. the ROM-01 GS?
 021- How can my ROM 3 GS + 8MB Sirius card do large file copying? 
 022- Where can I find a listing of Apple II socket, etc. pinouts?
 023- Where can I find Apple II diagrams?
 024- How do I add a video output level adjustment to my TrackStar?

From: Paul Guertin

001- Could anyone suggest a good project book for the Apple IIe.
     I'm interested in using an old box for tracking the
     temperature in a water bath.

Vernier software publishes a book called "How to Build a Better
Mousetrap" which contains 14 hardware projects for the Apple II. Project
#6 is a temperature probe connected to PDL0.

ISBN for the book is 0-918731-16-X.
Vernier Software ( )  
2920 S.W. 89th Street
Portland, Oregon  97225 USA
(503) 297-5317


From: Sheldon Simms

A good book is _Inside The Apple IIe_ by Gary B. Little. It isn't a
project book, but it does have a good chapter on using the Game I/O
connector for "electronics experiments."


From: Cyrus Roton

002- How can I use a thermistor (a resistor which has a variable
     resistance related to ambient temperature)  to read temperature
     on my Apple II?

You can connect a thermistor to a paddle input and supply a voltage to
the other end. Current flows through the thermistor to charge a .022 mfd
capacitor inside the apple2. When the paddle is read, the apple2
discharges the capacitor and resets a timmer. Then the cap is allowed to
charge. When the charge reaches the trigger level (3.2 volts) the timmer
is stopped and the count is read out.

The lower the value of the thermistor, the faster the charge and the
lower the count. Also, the higher the voltage, the faster the charge.  A
resistance of about 120K with a 5 Volt supply will give a count of about
250. You can add an external capacitor across the paddle input (to
ground) to increase the charging time (if needed)

 The formula is (charge) = (input volts) * (1 - exp(-t/RC))

So, you can use a supply voltage and external capitor as required to fit
the resistance value of the thermister (or other resistive component).
Probably, the best way to find the correct values woud be to try a
variety of values and plot the "count" as a function of the variable
resistance. Then compare the plot against the resistance curves for the
thermistor (probably not linear), and work out some conversion formula
to use in your program to correlate "count" to temperature.


From: David Empson

003- Can I use the same prototyping Slot Board for all of the
     different Apple II's with Slots?

Prototyping boards certainly would be the same for the II, II+, IIe, and
IIgs. The slots on all slotted Apple IIs are physically identical

There are minor differences between the slot signals on the various
machines and on some slots in the same machine, mostly affecting rarely
used special pins. (See Question 004 for more details on signal


004- What is the pin-out for the Apple II series Slots; and, what
     differences are there in Slot signals from machine to machine?
Here is a quick summary of the Apple II series Slot signals:

Pin 1: I/O Select ($Cn00-$CnFF, where n is the slot number).

Pins 2-17: Address bus A0-A15.

Pin 18: Read/Write.

Pin 19: unused on the II and II+.  On the IIe and IIgs, this has
composite horizontal and vertical sync on slot 7, and is unused on other
slots, except for slot 1 on the IIe only, which has a diagnostic
function to disable the oscillator on the motherboard.

Pin 20: I/O Strobe ($C800-$CFFF).

Pin 21: this is the RDY input to the micro on all machines, but it
behaves a little differently in the IIgs, or in a machine with a 65802

Pin 22: this is the DMA pin on all machines.  Again, there are special
issues for doing DMA on the IIgs which can cause compatibility problems.

Pin 23: this is used for the interrupt daisy chain (out) on all Slots
except 7. In the IIe only, this pin can be connected to the GR signal
(graphics mode enabled) via a motherboard modificatoin.

Pin 24: DMA daisy chain out.

Pin 25: +5V.

Pin 26: Ground.

Pin 27: DMA daisy chain in.

Pin 28: Interrupt daisy chain in.

Pin 29: Non Maskable Interrupt.

Pin 30: Interrupt Request.

Pin 31: Reset.

Pin 32: this is the INHIBIT pin on all machines.  This behaves
differently on all three machines: the II and II+ only allow the
$D000-$FFFF ROM area to be inhibited.  The IIe allows RAM to be
inhibited as well, but has strange interaction with main and auxiliary
memory.  The IIgs only allows this signal to be used if the machine is
running in slow mode.

Pin 33: -12V.

Pin 34: -5V.

Pin 35: unused on the II and II+.  On the IIe and IIgs, this is the
colour reference signal on slot 7 only.  It is unused for other slots in
the IIe, except for slot 1 where it provides a poorly documented
facility to disable the keyboard address decoding.  On the original
IIgs, slot 3 provides the M2B0 signal (Mega II Bank 0) via this pin and
it is unused on other slots.  The ROM 3 provides M2B0 for slots 1 to 6.

Pin 36: 7 MHz system clock.

Pin 37: Q3 - Asymmetrical 2 MHz clock.

Pin 38: Phase 1 clock (1.023 MHz).

Pin 39: something called "USER 1" on the II and II+, which can be used
to disable all I/O decoding if a modification is made on the
motherboard.  On the IIe, this pin provides the SYNC signal from the
micro, which indicates an opcode fetch.  On the IIgs, this pin provides
the M2SEL signal, which indicates that a valid slow memory access is in
progress.  This pin must be used by IIgs cards that decode the address
without use of the IOSEL, IOSTRB or DEVSEL pins.

Pin 40: Phase 0 clock (1.023 MHz).

Pin 41: Device Select ($C0n0-$C0nF, where n is the slot number plus 8).

Pins 42-49: Data bus D7-D0.

Pin 50: +12V.


from Rubywand

005- I've been getting Fatal System Error 0911 and when I do the
     internal diagnostic it gives a system bad : 09010001.
     Is there a fix?

     Fatal System Error 0911 and Self-Diagnostic Test 09010001 mean the
same thing: You are, very likely, experiencing an ADB Controller

     A guess would be that you are running a ROM-01 GS, probably a
ROM-00 machine which has the ROM-01 upgrade. If this is the first time
you've noticed the '0911 problem, it is likely that this is the first
summer you've owned and used this particular machine.

     Many early GS's come with an ADB IC which malfunctions over a
narrow range of relatively low temperatures. Rooms are normally cooler
during summer; so, this is when the error pops up most frequently. Some
users first notice a plague of '0911 crashes after adding a System
Saver-GS (which increases cooling).

    '0911 bombs can occur 'any time' but they usually happen at startup
and when doing OpenApple-CTRL-ESC accesses to the Desk Accessories
(CDA's, Control Panel, ...) menu. As the machine warms up, '0911 crashes
tend to become less likely.
     The bad news is that there is no 100% fix except to replace the
temp sensitive ADB IC-- hard to do since it is soldered to the
motherboard and, in any case, known-good replacements are difficult to

     As to _which_ ADB IC-- there are two, the ADB Controller and the
ADB GLU-- our notes say the ADB Controller; but, we could have easily
misidentified the function back then and the ADB GLU IC 'clicks' better
with memories of the fix. (The ADB GLU IC is a bit larger and easier to

Note: The easiest way to identify the temp sensitive IC is to apply the
fix (below) and see if it works. If it does, fine. If not, it is easy to
move the fix to the other IC. For now, my suggestion is to try the ADB
GLU IC first.

     Since the problem is coolness, a decent cure is to tape a small 12V
bulb (e.g. a 20-30 ma. panel light bulb) to the top of the ADB IC (a
square IC near the right front of the motherboard). Use duct tape and
try to enclose the bulb and IC in a kind of mini-oven. Run the leads
from the bulb to the +12V Fan power pins near the back left area of the

     The idea is to quickly warm up the IC. I used a scheme like this on
our early GS and 0911 bombs dropped from 4-5 per day to 2-3 per week. If
you can safely power the bulb via an external power module (e.g. a
calculator or radio 'AC adapter') so that the bulb can be ON at least a
few minutes before powering up the computer, 0911 bombs might disappear


006- My GS control panel keeps resetting to the defaults and
     forgetting the date between power-ups. What's wrong?

     Most likely, your battery-- also called the "BatRAM  battery" needs
to be replaced.  When the GS is OFF, the battery supplies power to the
clock and its attached 256-byte RAM. This small RAM is where Control
Panel settings are 'remembered'.

     If, upon power-up, the GS believes the Control Panel settings have
been messed up due to a low battery, it will reset the settings to their
default (check-marked) positions.


007- How do I replace my GS "BatRAM battery"?

     The standard GS battery is a 3.6V Lithium type rated at 1.2AH. It
is called the "BatRAM" battery because it keeps the Battery RAM and
Clock IC going when you turn OFF power. To get to the battery, you must
pop out the Power Supply.

     If you have a ROM 03 GS, you can slip out the old battery and slip
in 'one like it'. On the ROM 01 GS, you will need a Lithium battery with
leads you can connect to cut-off leads from the old battery-- about 3/4"
each-- remaining on the motherboard. Be sure to mark the "+" lead on the
motherboard with white-out.

     Night Owl Productions used to sell a convenient "Slide-On" Lithium
battery made by Tadiran. It came with springy ends that would slip over
the cut-off leads from the original GS battery.

     Radio Shack sells a few models of 3.6V Tadiran Lithium batteries.
Mostly, these have smooth ends and are intended to fit into a holder--
for example, one model is "AA" size. Connecting an insulated size AA
holder and using a size AA 3.6V battery is one way to handle BatRAM
replacement now while making future replacements easier.

     Another Radio Shack 3.6V Tadiran Lithium battery comes as a small
rectangular insulated pack with red and black wires going to a plug.
From the catalog illustration, it appears that the plug could be fitted
onto the cut-off leads if these were long enough to be shaped to match
the plug's connectors. (If you decide to have long cut-off leads, it's a
good idea to slip heat-shrinkable tubing over the leads to insulate them
for most of their length.)

     It may be that your best bet for getting a good BatRAM replacement
battery is All Electronics (800-826-5432; ).
Their last catalog lists two 3.6V 2.5AH Lithium batteries with wire
leads which should fit well in a ROM-01 GS for $3.50 each. They also
offer a 3.6V "AA size Lithium battery" ($3.50) which looks good for
computers with AA size holders.

     If you like, you can always solder, crimp, etc. insulated leads
going to some plug or socket which matches the connector of a particular
battery you'd like to use.  For connecting bare leads, Duncan Entwisle
suggested using the springy connectors from a Radio Shack electronics
experimenter kit to connect a new battery's leads.  Another way is to
use "wire nuts". Should you do any soldering to the cut-off leads, try
to avoid long heat exposure-- you do not want to melt the connection at
the motherboard.

     Make sure that the new battery's "+" lead connects to the "+" lead
on the motherboard. Since, possibly, you will be joining bare leads to
bare leads, you could end up with more bare wire than you are
comfortable with. Check that the bare leads do not touch anything they
should not. Bend the leads as required and position the new battery so
that nothing will bump into the Power Supply when it is replaced.

     The usual recommendation for this kind of work is that the computer
be OFF. This reduces the risk of damage should a bit of solder, a wire,
etc. fall onto the motherboard.

     GS users are sometimes shocked to discover that a replacement
battery may cost $8 to $13. This has led to suggestions that 2-3
standard 1.5V cells in a holder be used. While any number of lower-cost
replacement setups can work, this is pretty close to a classic 'you get
what you pay for' situation.  Regular 1.5V cell combos reportedly crater
in about a year. A 3.6V 1.2AH Lithium battery is routinely good for at
least 5 years.

     Our old Nite Owl battery is going on year 7 or 8. That's a lot of
years without having to worry about burst and leaking cells or needing
to pull the Power Supply and mess with swapping-in replacement cells.


008- Is there a program to record my Control Panel, etc. settings
     and restore them after the GS BatRAM battery is replaced?

Reference: FAQs Resource file R007BATRAMM.SHK

     Yes. A number of users have created programs to Save and Restore
BatRAM values. The one included as a FAQs Resources file is named
"BATRAMMER". It is in file R007BATRAMM.SHK. Use ShrinkIt or GS-ShrinkIt
to unpack the file.


From: Adalbert Goertz

009- How can safely clean out dust from my Apple II's
     motherboard, case, and expansion cards?

     I use a Dustbuster. Block one exit vent and aim the other vent as a
blower into the computer. That Dustbuster has strong lungs!


From: George Rentovich

010- I'm afraid that oxidation on pins may be causing bad
     contacts and memory problems. How can I remove the
     oxidation without resorting to sand paper?

     Tarn-X works great for removing oxididation from chip pins without
a lot of work or risk in harming the chips.

     Soak the chips in a shot glass until all black oxidation is gone;
then, remove the chips and put them in another shot glass with alcohol
to rinse. I use a third shot glass with alchol again to be sure and,
then, take out the chips and let dry.


From: Rubywand

011- Recently I was using my GS and smoke started coming from the
     inside. Now my ADB peripherals (KB and mouse) don't work! It
     looks like the smoke came from an 8-legged module in the upper
     leftmost corner right behind the composite video connector and
     ADB jack. What's wrong? How can I fix my GS?

     The module you are talking about is L2 "D-15C". This is an 8-pin
thing containing four inductors (coils). Three inductors are used. They
are in series with the ADB Desktop connector. Evidently, one of the
inductors burned out. This would explain the smoke and the loss of ADB

     The three inductors run ...

     pin 1 to  pin 8
     pin 2 to  pin 7
     pin 3 to  pin 6

     You can use an Ohm meter to detect which one is open. (Example: the
correct reading from pin 2 to pin 7 would, probably, be less than an
Ohm.) Since the pin2-pin7 inductor connects to +5V on the pin7 side, it
is the best candidate for a burn out should pin2 some how have been
shorted to ground.

Note: Jon Christopher reported that when his L2 module bombed it was due
to a short in a spliced-on KB cable. It turned out that the resulting
burn out fused some of the inductors together inside the module. So, if
you detect any break after such a burn out, it is probably best to just
remove the module and replace all three inductors.

     Replacing the inductors should be fairly easy, although it will
probably be necessary to remove the motherboard. The value of the
inductors is not critical, so 15-20 turns of small wire-- like wirewrap
wire-- wrapped on a pencil or screwdriver shaft will make a small coil
you can use. Make three coils.

     After removing the damaged L2 module, use an Ohm meter to check for
a short to ground at pins 1, 2, and 3. (If, as in the case of a short in
a spliced-on KB cable, you know where the short is/was, you can skip
this check.)  Eliminate the short before continuing.

     Solder your home-brew coils in place (pin 1 to pin 8 for the first
coil, etc.), put everything together, and your GS should be as good as


012- My ROM-01 GS has an odd postage stamp size circuit board
     tacked onto the motherboard near the front edge. What is the
     board for?

     The circuit on the mini-board is a low-gain 1-transistor amplifier
which seems intended mainly as a buffer/voltage-level shifter between
the 'old Apple' sound output of the Mega Chip and Op Amps which drive
the Speaker and Sound jack.

     On the underside of the motherboard, beneath the boardlette, a
surface-mounted resistor (SR1) has been scratched out. Leads from the
mini-board run to SR1's connection points as well as Ground and a +12V
supply point near Op Amp UM12.

     The circuit does not appear in the GS 'Hardware Reference ROM-01
schematics; but, it is shown in ROM-03 schematics. Some ROM-01 GS's do
not have the mini board; so, it seems likely that the circuit was
included on-motherboard in later ROM-01's and all ROM-03's. By the way,
the circuit was certainly installed at the time of manufacture and was
not part of the standard ROM-00 to ROM-01 upgrade.


013- I have 256kB on my 1MB Apple IIgs Memory Expansion Card.
     How do I add more memory and set the jumpers?

     The standard Apple IIgs 1MB Memory Expansion Card can be usefully
configured for 256kB, 512kB, and 1MB.

     For 256kB, the top left 8 sockets (i.e. the left half of the top
row) should be filled. No jumpers should be placed on the pins near the
lower right end of the board.

                         O O (no Jumpers)
                         0 0

     For 512kB, the entire top row of sockets should be filled. The
pair of pins should be jumpered.

                         O O
                         0-0 Jumper bottom pair

     For 1MB, all sockets should be filled. The top and bottom pairs of 
pins should be jumpered.

                        O-O Jumper top and bottom pairs

     To get the full IIgs mem card upgrade to 1MB you can order a kit of
24 256k x 1 41256 DRAM mem IC's from Alltech (760-724-2404) for


From: SuperTimer

014- I've heard that some have moved their IIgs's to PC tower cases.
     Is this hard to do?

     It is not hard to do at all...

     I mounted the motherboard with the expansion cards going horizontal
in relation to the ground (you need to drill some extra holes in the
tower case because the GS has different mounting holes than the PC). The
cards are light enough that they stay put this way.  The only time this
could be a problem is with unusually heavy cards, like the Focus or
MicroDrive units...

     The cards don't line up with the openings on the case, but that's
not a problem because Apple cards, unlike PC cards, have ribbon cable
extended DB connectors that can be mounted on the openings at the back
of the case...

     For the power supply, I rewired a PC power supply to feed the GS.
The voltages are the same, so simply match +5V with +5V, +12V with +12V,
-5V with -5V, -12V with -12V, and the grounds and your GS will be ready
to run!

     The PC power supply (250 watts) and fans have a GS is
more stable now than it was in its native case.  I recommend this
upgrade for those who feel up to it.  Use a full tower case for the best
results and most room to work with.


015- I recently picked up a spare GS from a flea market and
     would like to convert it into a portable. Has anyone done this?

     Yes. Tony Diaz has an article describing a couple conversions on
his web site at .


From: Erick Wagner

016- Where can I get Robot kits to use with my Apple II?

     If you have a an RS-232 interface (2400 or 9600bps) you might
consider a kit from Lynxmotion ( ). They sell
various robot and robotic arm kits that utilize hobby R/C servo motors.
Scott Edwards Electronics and several other companies sell devices that
allow you to control up to 8 servos per board.

     You'll have to write all of the software yourself (sending commands
to identify a servo and a position value).


From: Rubywand

     A good source of current information on robot making, Parallax
BASIC stamp programming, and related projects is Nuts & Volts Magazine
(800-783-4624; ).


From: Dick Pirong

017- Where can I get the chips to expand my AE GS-RAM III memory
     Expansion card to 4MB?
     The Applied Engineering GS-RAM III uses 20-pin "Zip" package 1M x 4
DRAMs (NEC D424400V-80 or OKI H5144024-70). Mike Morton led me to a
supplier in the Computer Shopper magazine.  (Thanks Mike.) The supplier
is L.A.Trade (800-433-3726; ).  I
now have a total of 5 megs in my ROM 3 and all is well.


From: Bill Whitson 

Related FAQs Resource: R022TRKSTAR.TXT (text file)

018- What is a TrackStar? Does it need special software?

     A TrackStar is a single board Apple 2 computer that plugs into an
expansion slot in a PC Clone. With this board (and an A2 disk drive) a
PC can run Apple II software. See the FAQs Resource file R022TRKSTAR.TXT
for details.



     Yes, TrackStar does need some software. I have it; it's less than
30k in a zipped file.


From: Rubywand

019- Could someone please post a resistor color code chart?

Color   Digit   Multiplier (when 3rd band)  Example 

Black     0       x1              --  Red Red Black =         22 Ohms
Brown     1       x10             --  Blue Grey Brown =      680 Ohms
Red       2       x100            --  Orange White Red =    3900 Ohms
Orange    3       x1000           --  Yellow Violet Orange = 47k Ohms
Yellow    4       x10000          --  Red Green Yellow =    250k Ohms
Green     5       x100000         --  Orange Orange Green = 3.3M Ohms 
Blue      6       x1000000        --  Red Yellow Blue =      24M Ohms
Violet    7       x10000000       --  ...
Grey      8       x100000000
White     9       x1000000000

Gold      -       x 0.1           -- Brown Brown Gold =      1.1 Ohms
Silver    -       x 0.01          -- Orange White Silver =  0.39 Ohms

Tolerance (4th band)

Red is           <5% (courtesy of Edhel Iaur)
Gold is           5%
Silver is        10%
no color is      20%

Example: Grey Red Orange Gold      is 82k Ohms  +/- 5%
Example: Brown Black Green Silver  is  1M Ohms  +/- 10%

Note: carbon resistors almost always err on the high side.


From: Mitchell Spector

020- What advantages does the ROM 3 GS offer vs. the ROM-01 GS?

     The ROM 3 Apple IIgs offers many minor enhancements vs. the ROM-01
which make the machine more functional and pleasant to use:

- You get a machine that is about 5-10% faster for GUI, floppy disk
  loading and RAM Disk operations (due to updated smartport firmware
  and System 5 tools being in ROM).

- A machine that is more flexible when working with AppleTalk and
  slots (you don't have to give up an extra slot and you can stick a
  card in slot 4 and still use the mouse in GS/OS).

- A nicer text Control Panel that lets you resize RAM Disk with a
  warm-boot and a cleaner way to size it too (no min/max size junk).
  Also a 'Mouse' menu and other existing things cleaned up and made

- A just over 1 megabyte of RAM built-in to start off with; so, you
  can have 5 MB of DMA compatible memory in total.

- The MB0 signal provided in slots 1 through 6, so you can stick
  in a Video Overlay Card _and_ Second Sight in together, and not
  worry about having to reserve slot 3.

- Hardware shadowing of text page 2 with Alternative Display Mode
 (no slowing down your system to a crawl when you see a screen full
  of 2's running 8-bit software).

- A newer ADB keyboard microcontroller with built-in sticky keys,
  keyboard mouse and compatibility with the indicator LEDs
  on extended keyboards.

- A removable Lithum battery (in a snap case. Just pop the old one
  out when your clock and Control Panel settings stop working).

- Less power consumption and electrical noise from the motherboard,

- A set of pins (location 'S1') on the motherboard to make the text
  Control Panel disappear, making your GS settings tamper proof where
  young children are around

    There are even a couple of more goodies, like the Step/Trace
commands in Monitor or the improved disassembler. Even if you are not a
programmer, they're handy for peeking at SHR graphics still in memory
(from Monitor hit 'S' and then the return key).

    Things like sticky keys and mouse keyboard come in handy too-- like
if you are eating or drinking with one hand, you can still reset the
computer using the other.

    The down side is that some old GS games and demos won't run. However
many of the more worthwhile ones have been patched.


From: Scott G

021- How can my ROM 3 GS + 8MB Sirius card do large file copying?

     An error in the Sirius manual (a 1 page paper) recommends that ROM
3 users remove one of the SIMM modules since the ROM 3 has 1MB and 8MB
is max. When I did this, the GS reported 8MB, but copying large groups
of files or large files (>800k) failed.  When I put the missing SIMM
back, the GS still reported 8MB, but the file copy problems vanished. 
It appears that the Sirius needs eight 1MB SIMM modules for 8MB even on
a ROM 3.


From: Charles T. Turley

Related FAQs Resource: R023PINOUTS.TXT (text file)

022- Where can I find a listing of Apple II socket, etc. pinouts?

     See the FAQs Resource file R023PINOUTS.TXT.


From: David Wilson

023- I have several different model Apple II computers ranging from
     a II+ up through a IIgs. Does anyone know where I can get
     diagrams for these machines?

     I know of three books with Apple ][+ schematics:

     Jim Sather's "Understanding the Apple ]["

    "The Apple II Circuit Description" by Winston D. Gayler
      published by Howard W. Sams & Co (ISBN 0-672-21959-X)

     Apple II Reference Manual (1979)


From: Mike Westerfield

    "Understanding the Apple II," by Jim Sather, has a complete set of
II+ schematics, as well as more information about putting them to use
than the official Apple manual.

     It's available from Byte Works  for $14.95. Check out our list of
software and books at And if you'd like a
printed copy of our catalog, just send me a snail-mail address.


From: Rubywand

     The IIe Technical Reference 1986 edition includes diagrams and an
annotated firmware listing. Probably, the IIc and IIc/IIc+ Technical
Reference manuals are similar to the IIe Technical Reference-- not sure,
since I have not seen a IIc manual.

     The Apple IIgs Hardware Reference has a good set of schematics. The
First Edition covers the ROM-01. The Second Edition covers ROM-01 and
ROM 3.  Unfortunately, there is no firmware listing.


From: Rubywand

024- I got a TrackStar E and plugged it into our old PC. It seems to
     be booting a diskette okay from an attacked Disk ][ drive; but,
     the composite video doesn't give any kind of display on a
     monitor I know is good. Someone said I need to add a video
     output adjustment. How do I do this? 

     Most likely, the video level from TrackStar's composite output is
too high. On an Apple II+, this would be no special problem because
there is a mini-pot to adjust the video output level. If either monitor
had an adjustment for video level input, it would not be a problem,

     A check of the TrackStar board revealed that composite video comes
from the emitter of a transistor connected to ground via a 75 Ohm
resistor. This output goes through a small RF choke to the RCA socket on
the back of the board.

     The cure is to replace the 75 Ohm resistor with a pot. Here are
step-by-step directions for swapping in a Video Output adjustment ...

1. On the back of the board, find the trace going to the 75 Ohm resistor
and the choke. (The choke is close to the RCA socket. The 75 Ohm
resistor is near the choke.)  Cut the portion of the trace going to the

2. De-solder and remove the 75 Ohm resistor. (You can snip it off if you

3. On a 200-300 Ohm potentiometer-- I used a, roughly, 250 Ohm
mini-pot-- connect three leads. (The length of the leads depends upon
whether you have some place on the back of the PC to mount the pot or
just plan to put some tape around the pot and let it flop around near
the board. I don't know how long the leads can be before noise pickup is
a problem. It seems like a good idea to keep length within about 8" or

Use three different color wires-- say White, Green, Black. Viewing the
pot from the back, connect White to the Left tab, Green to the middle
tab, and Black to the right tab. (Mainly, the Green wire needs to be on
the middle tab.)

4. Solder the Green wire to the end of the choke which used to be
connected to the 75 Ohm resistor-- i.e. the end _not_ going to the RCA

Solder the White wire to the place the 75 Ohm resistor used to be
connected which used to connect to the choke before the trace to the
choke was cut-- i.e. this is the point which goes to the emitter of a
nearby transistor.

Solder the Black wire to the other place the 75 Ohm resistor used to be
connected. This is the Ground end.

Note: Mixing up the White and Black leads is okay. The only reason for
connecting them a certain way is so that a clockwise turn of the pot =
increased Video Output.

The circuit you end up with looks like this ...

 Pot                         /
  _______ White_____________/ emitter of transistor
 Z <----- Green -----------UUUUUUUUU-------- to RCA socket center pin
 Z                          Choke             Composite Video Output
 Z_______ Black____

5. Insert the board. Find some place safe to mount the pot or let it sit
so no leads or metal parts touch any circuit. Connect the monitor and
power up the computer. Start TrackStar and adjust the pot and monitor
for a good display.