Resurrection / Debugging of an Apple II or II+  
  When a Apple II or II+ sytem gets released from a long term storage itīs recommended to examine that system very carefully to avoid damage from the involved parts and interfacecards.  Itīs srictly recommended to followup exactly this line of procedures.
One of the reasons for this procedures is to narrow down possible reasons of malfunction.
That saves a lot of time and besides it also is a kind of standard routine that helps to detect most of the common problems that may occur when a system is resurrected.


The very start is to prepare the tests:

Unplug all interface cards and markup at the card with an adhesive label the slot where the card has been unplugged from.
All cards shall be stored in antistatic bags while remaining unplugged due to the fact that quite a lot of that cards contain static sensitive chips.

Here a picture of the mainboard and some additional informations about the functions of the chips on board:


At this current moment the only information needed is the "location notation":
at the very left side the mainboard contains "notation" starting at bottom ( front side ) with the letter "A"

towards the top ( rear side ) to the letter "K" amd the notation at the very bottom row starting at the left side

with the number "1" towards the right side with the number "14".
All so called "locations" are referring to this notation system. For example:

The 2 transistors of the base oscillator "Q1" and "Q2" are located at A1.

At the Mainboard there are 3 rows of RAM chips:

Row 1 is located from C3 to C10 and itīs responsible for the memory from 0kB to 16 kB.

Row 2 is located from D3 to D10 and itīs responsible for the memory from 16kB to 32 kB.

Row 3 is located from E3 to E10 and itīs responsible for the memory from 32kB to 48 kB.


The rest of the memory from 32 kB to 64 kB is located at the so called languagecard that is normally inserted at slot 0.

For the very beginning of the tests itīs recommended to start with the very basic system that is required to boot up to

the prompt at the display:

This means:

a)  no interfacecard inserted

b)  only first 16 kB of RAM inserted ( row 1 )

c)  keyboard is connected to the mainboard at socket at location A7.


Be careful when uplugging the RAM chips ! They are very sensitive to static discharge and therefor they must be

handled very careful. Immediatly after unplugging a chip it should immediatly be stored at a antistatic foam.
Itīs recommended to keep them in the same order of rows as they have been removed from the mainboard.


Before we start with the testing some additional information about the common RAM chips:

Itīs very strong recommended that all RAM chips in one row are as similar as possible ( same kind, same manufacturer ) !


In general all chips have common kind of marking printed on top of the chip: XX 4116 -nn


      XX = Manufacturer
      4116 / some more rare times only 416
      -nn = timing

All chips in one row shall be from same manufacturer !

4116-15 for example specifies timing to be certified at 150 nano seconds
2 for example specifies timing to be certified at 200 nano seconds
3 for example specifies timing to be certified at 300 nano seconds
so in that group above the
-15 is fastest


All RAM chips within one row must be of same kind of speed ! This rule overrules the following manufacturer rule !
So first order selection is speed and second order selection is manufacturer !

Another point: All chips with rear / front orientation have pin 1 of the chip at the front ( bottom ) right side and

at that chips counting pins is counterclock wise.

So make sure that at the first row this general rules are obeyed.
If your rows are containing mixes of different manufcturers try to get "clean rows" from only one manufacturer.

If you are forced to mix chips - do this with the memory of the language card !
In case of doubt - if you have "clean row" at the languagecard but mixed memory at the mainboard swap that

rows that way that the unmixed row is at the mainboard and the mixed one is at the language card.


"clean rows" towards front - mixed rows towards rear of the computer !

If you have to order memory from any kind of source try to get a "clean row" meaning a set of 8 chips from same

manufacturer and same speed !


So now back to the testing:

Under normal conditions when switching on power at an Apple II or II+ with 16 kB of memory ( only first row of
memory plugged in the mainboard ) the computer should issue a short beep and then display the message
"APPLE ][" in the top row centered and  the promt "]" should be at the left side 2 rows lower blinking and waiting
for input.

If this does not happen the problem may be split in 7 groups of problems:

1 ) Voltage
In most cases such a mistake will result to no display at all.


2) CPU

In most cases such a mistake will result to no display at all.


3) Adressingbus

In such a case in general the display will crash and only display four or eight large vertical

orientated squares or square bars.


4) Databus

In such a case in general the display will crash and only display four or eight large vertical

orientated squares or square bars.



5) RAM chips


In such a case in general you will get a display of "splashing random characters".


6) ROM chips

If the trouble is caused by the ROM in most cases the computer will crash to a monitor promting sign
 "*" and several lines of monitor codes might also be displayed.


Depending to the kind of error related to the number given above and to the tools you have availiable

there will be different kinds of solution to narrow down the problem to a specific chip.

1 )

Well in this case - and itīs one of the very first things to check out - by measuring the voltages direct at the
voltage input plug of the mainboard. You should set your multimeter DC 20 Volt.
The black testing cable shall be positioned eiter at the left od the right lower ( frontside ) of the powerplug

at the pin marked as Ground. The red testing cable shall be used for measurements.
it then should display the demanded voltages in a range within 6% of the specified volts.

             - 12,8 Volt to - 11,2 Volt


              + 4,7 Volt  to + 5, 3 Volt 



   - 4,7 Volt to - 5,3 Volt


   + 11,2 Volt to + 12,8 Volt


If one of the voltages or more do not match within specified values the power supply unit must be corrected in next step

to avoid damage to the ICīs ! This is also valid if the power supply unit itself issues unusual noise or abnormal smell.
In case of smell the problem is normally caused by leaking electrolytic capacitor. In such case itīs recommended to issue a task called "recapping" the power supply - which is a term for exchange of the most electrolytic capacitors.


In a few days i will add / update this page with a detailed description of this specific task.

If you have an oscilloscope and are a bit experienced itīs also not a bad idea to check the voltages at various measurement points

in the front rows B and C and hunt for so called "spikes" that may disturb randomly the function of the computer and indicate that

a capacitor is not any more within its specified limits of ESR value.





In case of a damaged CPU there is only one solution: exchange of the CPU and replacement of the damaged IC.
Itīs recommended to use for replacement -if possible - a CPU of same kind ( type and manufacturer ).




In case of adressing port malfunction one or more of the 3 adressing port chips 8T97 at position H3, H4 or H5 is responsible for the trouble.
The easiest solution would be to swap a spare similar 8T97 chip step by step through all 3 positions and  try by that to identify the damaged chip.
Depending to the version of mainboard in later mainboard versions instead of the 8T97 the chips have been replaced by 74LS367 chips.
In such a case of course the replacement chip also should be a 74LS367.




In case of trouble with the databus there are 4 sources of trouble possible:
a) one of the databus buffering chips 74LS174 at location B5 or B8 might be damaged and must be replaced.
b) one of the databus from RAM to videosection chips 74LS194 at location B4 or B9 is damaged and must be replaced.

c) depending to the version of mainboard you have at the right side from the CPU ( away from the side heading to the power supply )
    is either one chip labeled as 74LS244 at position H10  or 2 chips labeled 8T28 at position H10 and H11 might be damaged and

    by swapping the responsible chip with a spare chip of the exactly same typ  might solve the problem.




In case of this kind of trouble you might swap chip by chip one RAM chip after the next chip in the row C till all chips of the row have been

examined and after each swap trying to boot up by a short power up of the system to examine if the system solves the boot up
procedure with a short beep and display of the expected screen with Apple ][ title and prompt.


While performing this task there are 3 important things to pay attention:
Donīt stress or bend the pins of the chips too tough - this may case a pin to break of the chip !
Pay upmost attention while reinserting the chip that every pin slips exactly in itīs default place at the socket.
Avoid that a pin bends and slips below the chip while insertion od that it slips besides of the socket !
Pay attention to the correct orientation of the chip ! The notch must be at the side towards the keyboard !
These three kind of mistakes are the most commen errors causing a chip to become destroyed !

If you have a complete working row of working chips put the row aside at a special place on the antistatic foam and examine the

next set of chips as a row by the same procedure at row C till you have a complete working row of RAM chips and then repeat his procedure with the third row again in the row C and after that the row of chips from the language card. After you have a final set of 4 working rows of RAM chips you may add the second row of chips in the row D and after a power up checking correct function you may add up back the third row at E again

followed by a check of power up procedure hunting for the correct boot up display.

Then you may add up the languagecard in slot 0 and the chip at position E3 is relocated to the spare socket at the languagecard and the cable must be plugged in at the socket at position H3 and before powerup please check again the correct orientation of the relocated RAM chip and the cableplugs at both ends and then again check by boot up procedure if the correct screen is displayed.




If a ROM is bad in general the adresses displayed in the previous line before the monitor prompt are within a similar range.
This kind of mistake splits in general into 2 different reasons:

1 - the adressing itself

2 - a damaged ROM-chip.
2 can be verified rather easy by swapping the ROM chip with a known good one. The repair might not be that easy....

Itīs nowadays not that easy to get a replacement ROM but at the moment there are still replacements out there.......
the alternate chance for repair would be to replace the ROM chip by a programmed EPROM ( 2516 or 2716 )

- but you must pay attention ! The pinouts of the ROM and the EPROM are not same !
If you perform such a replacement you must perform some minor changes to the ROM to secure correct function.
This part must get completed by the decription....


If the mistake is related to point 1  ( the adressing ) there are in general 2 possible sources for this kind of trouble:
The main trouble might be caused by a damaged 74LS138 located at F12

and the second possible point of trouble might be a damaged 74LS08 at position H1.


The next step after this will be to add the diskcontroller to slot 6 and try to boot from disk !
First try to boot the DOS masterdisk or a ProDOS master disk.
Next if you have a testing disk like the dealers confidence disk or a Master testdisk or a testdisk from XPS then you should

run all tests including the memory tests ( also at the languagecard tests )

then the keyboard test

the display test

the ROM tests.


Before adding additional cards itīs also recommended to check the function and speed of the attached diskdrives.

This kind of procedures is explained at this pages and itīs follow up pages.





Then you may start adding the remaining cards step by step to their slots

preferrably to their default slots:

sloot 0 allready occupied by languagecard or 16 kB RAM card.

slot 1 => Printer Interface card
slot 2 => Serial or super serial interface card

slot 3 => 80 column card

slot 4 => Z80 CPU / CPM card or alternating CPU card.

slot 5 => soundcard or additional card for storage ( RAMdisk card, Controller for Harddisk IDE or SCSI  or second disk controller card )

slot 6 allready occupied by diskcontroller

slot 7 => special videocard or RGB card or additional card for RAMdisk or Harddisk interface.

Just for a hint of interpretation what trouble causes which kind of screen.....
Here some common "crash" boot screens and explenation of the related problems below that screenshot:

( some comments will be added in next days ! )

  This kind of screen or similar black/white screen is displayed in very early bootup stage if adressing line or dataline is not working. This kind of mistake is not related to a single RAM chip but rather more to the chips controlling the data- or adressing busses ! Itīs not even able to display the characters so also that bus between Char ROM and RAM is also affected.   This kind of screen or similar black/white screen is displayed in very early bootup stage if adressing line or dataline is not working. This kind of mistake is not related to a single RAM chip but rather more to the chips controlling the data- or adressing busses ! Itīs able to display the characters so that bus between Char ROM and RAM is OK.  
  This kind of screen or similar black/white screen is displayed in later bootup stage if adressing line or dataline is not working. This kind of mistake is not related to a single RAM chip but rather more to the chips controlling the data- or adressing busses ! Itīs not even able to display the characters so also that bus between Char ROM and RAM is also affected. In such case itīs in most cases related to the Databus and not the adressingbus.      
      This kind of screen appears if the bootup procedure is nearly completed
- but a stuck key feeds the computer input permanent preventing the
systems to finish and remain at the promt waiting for input.
  This kind of crash to memory in monitor mode might occur if a programm crashes to bad RAM by "out of memory"-error and some similar kind of screen may also apear if the system crashes resulting from damaged ROM.      
  This kind of display may show after bootup is completed when starting a game with hires screen and if there is a bad RAM chip within the second or third row of RAM that is containing the Hires drawings of the game.   This kind of screen appears after bootup has completed - but the access to the character ROM is disturbed or damaged and text getīs displayed with wrong characters.  
  This is a problem commen at the German Apple europlus:
Itīs displayed if the Apple II europlus has the German Character Rom inserted without a switch that eneables to choose between US and German characters.
  This screen is displayed if the 72LS02 at position B14 is damaged.  
  This kind of display may show after bootup is completed when starting a game with hires screen and if there is a bad RAM chip within the second or third row of RAM that is containing the Hires drawings of the game.   This is displayed if the Monitor canīt catch the vertical Sync-signal within the videosignal.
In most cases it can be solved by adjusting at the Monitor.









Description of "normal" bootup behaviour:

i remember that several months ago i made in a thread a complex description to the booting process of a computer in general and explaining the steps performed within this process...

for the second question the correct answer is also not that simple...
so in short the row of steps performed when the apple II is switched on ( and that is valid to nearly every computer )
1. power up and CPU starts performing arbitrary cycles of instruction code....
2. the cpu starts to read and perform the instructions in the so called "BIOS"-ROM ( in the apple II the F8-ROM - its called there the "autostart" ROM sometimes... )
BIOS is the abreviation from Basic Input Output System
3. reading this ROM tells the cpu how to operate the accesses with the peripherial devices ( like devices attached in the slots - i.e. interfacecards like the printercard or the DISK II Interfacecard )
4. while the computer performs this reading it performs besides a short memory check...
in modern computers this self check is more complex and ends up with a short "beep"...
at the apple II this task is smaller and ends up with a short "beep" too
5. If no disk-drive-controller is inserted - that will be the point where the computer will display the Basic-prompt and wait for instructions.....
6. If a disk-drive-controller is inserted the computer then will try to load a Disk-Operating-System ( i.e. DOS )from the diskette inserted in the drive .... ( as explained formerly thats the point were the DISK II Drivelight turns on and the motor starts spinning and the door of the drive should be closed gently to protect the centerhole against damage... ) and the drive will then start to read from the disk... thats indicated by the stepping of the read/write-head accompanied by some slight sliding-noise when the head slides backward and forward with its "sled" inside the drive.... before that process starts up you hear a short task of "knocking"-noise with short sled-moves because the head is "recalibrated" drawn back to the very outside of the disk and searching there for the track zero .... this task is repeated every time the disk looks up for a specific track and does not find it immediatly ....
7. After the Disk-Operation-System has been loaded entirely into the RAM of the Computer the conputer will look at the diskette if there is a automatic startup-program that shall be performed....
just as sidemark: DOS is not limmited to the so called DOS at the apple II - in fact proDOS, UCSD and CPM are also
Disk-Operation-Systems ....
If the Disk does not contain a DOS-System or if the System-tracks are damaged ( i.e. are not entirely readable ) the computer remains with that spinning noise for quite a while - before it will suspend from attempting the disk and the computer sometimes (!) generates a error-code to the display... ( that depends to the point where the computer gets stuck in the task .... )
8. If the task of reading the DOS to RAM is completed successfully and no startup program is at the disk the computer stops the tasks and turns up the BASIC-prompt ...
9. If the Diskette has a startup-program ( at the DOS-system called "hello" - it will perform that program and turnup with the results of that program and then display the Basic-prompt.... ( for example - some "hello"-programs perform a catalog-instruction and then list up the files contained in the disk or launch a game )

So if you turn on the computer and do not get the Basic-prompt the computer has stuck up somewhere with in the one or other task listed above....

for example a common trap is trying to launch a CPM-disk and no Z80 Card inside at slot 4....
or inserting a disk with no DOS-System on the disk...
another trap in this time is that diskettes are not equipped with eternal life...
if stored in wrong mannor or due to age a disk might "loose" its contents....
this is related to the fact that magnetic information on the disk surface is not really
"permanent" - it might weaken by age... this can be avoided by using the disks time by time
and rereading and resaving the contents... this "refreshes" the contents of the disk...



when booting from a disk the quality of the used disk ( specially the centering hole )
might be important:

the whiring is in fact the spinning of the motor and the turning of the disk material in the cover.....
with growing experience you might determine if the disk is aligned correct in the drive....
some drives spin up the motor when inserting the disk to help align the disk in proper position ( usually those with half-height construction and some clones of the APPLE DISK II .... the APPLE DISK II does not do this normally....
the spin up of the motor is performed in this drives when the diskette passes an internal light barrier...
the purpose is not to damage the centerhole when closing the drive because most old diskettes ( specially the cheaper ones ) are rather not very hard and mis-aligning the diskette might damage that hole... better and more expensive diskettes have on the one or other side an aditional plastic ring to protect the alignment center hole...
at the apple two it is therefor usefull behavior to close the front door while the motor is spinning - to protect the diskette for expanding the lifetime of the diskette...





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