Apple II Minus Question
Bryan Parkoff
model that it starts with Old Monitor Routines rather than AutoStart
Routines. Do white horizontal block like GR (low resolution) appears in the
screen? Or...Do white horizontal block like TEXT ("@@@@" and "??????")
appears in the screen?
If it is GR, must you always press RESET before it returns to "*"
prompt?
First, you turn on Apple II Minus.
Second, odd lines (1, 3, 5, 7, 9, etc) appears "@@@@@@@@" and even lines
(2, 4, 6, 8, 10, etc) appears "????????". They are all inverse.
Third, "*" prompt appears in 24th line.
Sometimes, "???>@.?1??<??" show. Do you suspect that it may be bad RAM?
Or it may be static leakage?
Are all "00 00 00 00 00 00 00 00" store in odd pages between $0000 and
$BFFF and "FF FF FF FF FF FF FF FF" store in even pages between $0000 and
$BFFF? If each page do show like "01 01 01 01", "7F 7F 7F 7F", "E1 E1 E1
E1", "FE FE FE FE", or etc. I claim that all static RAM chips are bad. It
is why I have Apple II Minus and Apple II Plus motherboards that are
defective in my hand except extra Apple II Plus is working OK.
I bought all 7xxxx chips and RAM chips from electronic store. I removed
all old chips out of all sockets. I threw them in the trash. I put new
7xxxx chips and RAM chips in all sockets. I did test, but the result is
still the SAME. Such as GR and HGR are not working (never turn on, but stay
in TEXT only).
It may be motherboard that is bad. Probably some resistors, capicators,
and other electronic parts are bad however all chips are working fine on
another Apple II+ motherboard. I do have Apple II+ repair manual. It does
provide me a lot of information, but it does not specify where defective
occurs. It suggests to use electronic diagnostic tools to measure voltage,
resistors, currents, etc on the motherboard.
Please suggest which electronic diagnostic tools that is very worth for
me to buy before I can be able to isoslate defective parts. If I have found
defective, I would be ABLE to repair. Please advise.
--
Bryan Parkoff
Bryan Parkoff
Rubywand
The best diagnostic tool is usually the computer itself-- you try
different things and notice what it does.
Maybe some RAM interface IC is loose or defective. Try pulling and
cleaning the pins of the 74LS174's at B5 and B8 (near the front of the
motherboard). Do the same for the 74LS257's at B6 and B7.
If that doesn't fix things, try pulling and resocketting every IC. It's
pretty common for old computers to develop problems due to loose IC's or IC's
which have developed corrosion on pins. (Out II+ did that about a month ago.
Pulled and cleaned the IC's and the II+ has been working fine since.)
Rubywand
Bryan Parkoff
Didn't you understand? I trashed all old 74xxx chips and static RAM
chips. Cleaning chip's pin is not worth. I bought new 74xxx chips and
static RAM chips from electronic store a month ago. They are IDENTICAL to
the OLDEST 74xxx chips and static RAM chips.
How do I clean each socket's hole (Not Pin)?
--
Bryan Parkoff
"Rubywand" <ruby...@swbell.net> wrote in message
news:403E7B43...@swbell.net...
Vince Briel
> chips. Cleaning chip's pin is not worth. I bought new 74xxx chips and
> static RAM chips from electronic store a month ago. They are IDENTICAL to
> the OLDEST 74xxx chips and static RAM chips.
> How do I clean each socket's hole (Not Pin)?
Inserting IC's into the sockets creates a friction that cleans and almost
scrapes the contacts. It's the only way I know to clean sockets. You've
replaced the RAM and 74xxx series IC's, so I'd try swapping out more, like
the CPU, and anything else you can find. It might not be an IC but a
component like a blown cap, or maybe even a bad solderpoint. Check over all
solder spots with a magnifying glass. Look for cracks in the solder.
Cheers,
Vince
--
Replica I
The Apple I clone
http://www.applefritter.com/apple1/members/replica1/index.htm
Michael J. Mahon
>Inserting IC's into the sockets creates a friction that cleans and almost
>scrapes the contacts. It's the only way I know to clean sockets. You've
>replaced the RAM and 74xxx series IC's, so I'd try swapping out more, like
>the CPU, and anything else you can find. It might not be an IC but a
>component like a blown cap, or maybe even a bad solderpoint. Check over all
>solder spots with a magnifying glass. Look for cracks in the solder.
All good suggestions.
I once had a //e that failed in strange ways, and it turned out to
be a bypass capacitor near the 65C02. One wire had become
fatigued (too many Zip Chip swaps ;-) and was broken right at
the board.
A ][+ (please, there is no such thing as a "minus"), once
stopped displaying color because the crystal went out of
spec.
Hairline PC trace cracks can also be an issue, depending on
the mechanical history of the board.
Swapping chips wholesale is generally not a good idea--"If it
ain't broke, don't fix it."
Rubywand's suggestion that diagnosis should proceed from
an observation of the symptom(s) is always good advice.
As you have observed, the Apple ][ does not have a hardware
reset (unless a Disk ][ controller is present), and must be
manually reset to get into the monitor.
Don't worry about DRAMs (dynamic, not static) coming up
in funny states--that's common.
-michael
Check out amazing quality sound for 8-bit Apples on my
Home page: http://members.aol.com/MJMahon/
Wayne Stewart
What you see on screen on a machine with the monitor ROM doesn't seem
to be too indicative of anything. Different machines that function
flawlessly and pass all the tests I've ever given them seem to have
different gargage on the screen when I turn them on.
When you were replacing chips, did you lift up and press down the 6502
and ROMs.
What is the machine doing or not doing? If you do a Control-B then press
Return do you get into basic? Can you boot and rum a program? If you can
run a program, have you tried any RAM test software?
Wayne
Rubywand
>
> Rubywand,
>
> Didn't you understand? I trashed all old 74xxx chips and static RAM
> chips. Cleaning chip's pin is not worth. I bought new 74xxx chips and
> static RAM chips from electronic store a month ago. They are IDENTICAL to
> the OLDEST 74xxx chips and static RAM chips.
> How do I clean each socket's hole (Not Pin)?
>
Missed the part about chucking all of the 74xxx chips. Usually, that isn't
a good idea. When you do a wholesale swap of so many chips, the chances that a
74xxx on a motherboard is bad are about the same as getting a messed up 'new'
74xxx chip.
Since you say the computer acts the same, it looks like you lucked out and
got good IC's.
Does the computer do anything when you press RESET? If not, the RESET
switch may not be working Or the connection between the RESET key and the 6502
RESET pin may be broken (Or, the connection may be shorted to Ground).
If pressing RESET doesn't have any effect, try pressing the key several
times quickly-- if the switch is dirty or slightly defective, that may get you
a connect and a RESET.
BTW, also try doing a CTRL-RESET.
A quick check for your RESET switch and connecting lines is to use a Volt
meter. With power ON, check to see whether or not pressing RESET causes pin 40
on the 6502 to go to from about 5V (RESET not pressed) to 0V (RESET pressed).
Rubywand
Bill Garber
: Bryan Parkoff writes ...
: >
: > Rubywand,
: >
: > Didn't you understand? I trashed all old 74xxx chips and
: > static RAM chips. Cleaning chip's pin is not worth.
: > I bought new 74xxx chips and static RAM chips from electronic
: > store a month ago. They are IDENTICAL to the OLDEST 74xxx
: > chips and static RAM chips.
: > How do I clean each socket's hole (Not Pin)?
: Missed the part about chucking all of the 74xxx chips.
: Usually, that isn't a good idea. When you do a wholesale
: swap of so many chips, the chances that a 74xxx on a
: motherboard is bad are about the same as getting a messed
: up 'new' 74xxx chip.
I have a II+ with some new plastic 4116 rams and some of
the old gold pinned rams, and it runs fine. What I mean is
that I agree with Jeff whole-heartedly.
: Since you say the computer acts the same, it looks like
: you lucked out and got good IC's.
I agree again, however, if a new ram is bad and placed into
the very same bank, then it is possible, although highly
unlikely, that a bad ram could still be the problem. Have
you tried running on 4K or 8K ram and NO cards in the slots?
This may or may not help, but I recently received
a Platinum //e in which someone had installed a
Character Generator on a programmed 2732A. It was
a 450ns eprom, too slow for the Apple II to use.
According to my source, 390ns MAX is acceptable.
I found the ROM CharGen, read it, burned it to a
new 250ns 2732A, installed it and VOILA!, the //e
runs like a charm. For clarification, with the slow
eprom CharGen, the //e booted, but nothing displayed
on screen and would not continue after checking the
drive for a disk. Once a good CharGen was in place,
the disk loaded as usual.
Bill @ GarberStreet Enterprizez };-)
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Bryan Parkoff
> >Inserting IC's into the sockets creates a friction that cleans and almost
> >scrapes the contacts. It's the only way I know to clean sockets. You've
> >replaced the RAM and 74xxx series IC's, so I'd try swapping out more,
like
> >the CPU, and anything else you can find. It might not be an IC but a
> >component like a blown cap, or maybe even a bad solderpoint. Check over
all
> >solder spots with a magnifying glass. Look for cracks in the solder.
RAM chips, ROM chips and CPU chips are working fine on other Apple II
motherboards. They are in fair condition. I suspect that motherboard is
very bad, but it is in a VERY GOOD CONDITION. Didn't it make sense? It has
to do with resistors, capicators, and other electronic parts including
broken traces.
>
> A ][+ (please, there is no such thing as a "minus"), once
> stopped displaying color because the crystal went out of
> spec.
not really Apple II Plus. I do understand that there is no such label that
says "Apple II Minus". It always says "Apple II" It helps us to recognize
"Apple II Minus" and "Apple II Plus" rather than "Apple II" and "Apple II
Plus".
> As you have observed, the Apple ][ does not have a hardware
> reset (unless a Disk ][ controller is present), and must be
> manually reset to get into the monitor.
Can you explain, "Apple II Minus does not have RESET hardware?" Do you
mean that 6502 CPU does have RESET built in, but Apple II's keyboard has
RESET key while it is not WIRED to 6502 CPU? It is why RESET key is not
working that is never hooked up to 6502 CPU. Does it mean that everyone
owns Apple II Minus must always turn off and on power every time to reboot
Apple II Minus?
I turned on Apple II Minus before HGR is turned on with both 12 black
and white horizontal lines in the screen. No assembly prompt, Integer /
AppleSoft BASIC prompts are shown. I tried to hold and press CTRL-B keys to
return to Integer BASIC from Old Monitor Routines, but nothing is working.
Is it true that AutoStart Monitor Routine and Old Monitor Routine zeroes
"FF FF FF FF" in each even page and "00 00 00 00" in each old page? Or...Is
it the way how RAM chip zeroes "FF FF FF FF" and "00 00 00 00" in both
even/odd pages before power is turned on? It is impossible to show garbage
characters in each RAM chips. On unenhanced Apple //e has "FF FF FF FF" and
"00 00 00 00" in both even/odd pages, but it NEVER has any garbage
characters unlike Apple II does. I don't know if it is true that it is done
to z尻｢ by neither RAM chip or Monitor Routines.
--
Bryan Parkoff
Wayne Stewart
> I turned on Apple II Minus before HGR is turned on with both 12 black
> and white horizontal lines in the screen. No assembly prompt, Integer /
> AppleSoft BASIC prompts are shown. I tried to hold and press CTRL-B keys to
> return to Integer BASIC from Old Monitor Routines, but nothing is working.
If you don't get a * with a flashing square beside it then Control-B
and Return won't do anything. If you do then maybe some of the keys
aren't working. You should be able to see if those three keys are
working, provided of course you have a monitor prompt.
Have you tried swapping in an autostart ROM to see if it'll boot a
utility disk?
Wayne
Bill Garber
"Wayne Stewart" <way...@telus.dotnet> wrote in message
news:ZTU%b.23970$A12.17873@edtnps84...
I already told him that if he is seeing the checkerboard
pattern that the cpu is not getting power. It is the same
on all Apple IIs. Take out your cpu and turn it on. You'll
see what he is getting.
Michael J. Mahon
>> A ][+ (please, there is no such thing as a "minus"), once
>> stopped displaying color because the crystal went out of
>> spec.
> It is OKAY for me to say "Apple II Minus" or "Original Apple II". It is
>not really Apple II Plus. I do understand that there is no such label that
>says "Apple II Minus". It always says "Apple II" It helps us to recognize
>"Apple II Minus" and "Apple II Plus" rather than "Apple II" and "Apple II
>Plus".
The reason for nomenclature is clear communication. Making up
new names for old things is not generally a good idea. I know
what you mean, but "Apple II" already carries that meaning.
>> As you have observed, the Apple ][ does not have a hardware
>> reset (unless a Disk ][ controller is present), and must be
>> manually reset to get into the monitor.
> Can you explain, "Apple II Minus does not have RESET hardware?" Do you
>mean that 6502 CPU does have RESET built in, but Apple II's keyboard has
>RESET key while it is not WIRED to 6502 CPU? It is why RESET key is not
>working that is never hooked up to 6502 CPU. Does it mean that everyone
>owns Apple II Minus must always turn off and on power every time to reboot
>Apple II Minus?
I should have said the original Apple II doesn't have a _power on_ RESET.
The RESET key works just as on any other Apple.
What it means is that the original Apple II is not in a well-defined
state when you turn it on. You must manually press RESET to
put it in a well-defined state.
When the Disk ][ Controller was designed, it incorporated a power on
RESET circuit which resets an original Apple II at power on--and
automatically boots a disk if the Autostart ROM is installed.
> I turned on Apple II Minus before HGR is turned on with both 12 black
>and white horizontal lines in the screen. No assembly prompt, Integer /
>AppleSoft BASIC prompts are shown. I tried to hold and press CTRL-B keys to
>return to Integer BASIC from Old Monitor Routines, but nothing is working.
You must first press RESET.
> Is it true that AutoStart Monitor Routine and Old Monitor Routine zeroes
>"FF FF FF FF" in each even page and "00 00 00 00" in each old page? Or...Is
>it the way how RAM chip zeroes "FF FF FF FF" and "00 00 00 00" in both
>even/odd pages before power is turned on? It is impossible to show garbage
>characters in each RAM chips. On unenhanced Apple //e has "FF FF FF FF" and
>"00 00 00 00" in both even/odd pages, but it NEVER has any garbage
>characters unlike Apple II does. I don't know if it is true that it is done
>to z K¢ by neither RAM chip or Monitor Routines.
No, those are just the power-up states of the DRAM chips.
Bryan Parkoff
> > I turned on Apple II Minus before HGR is turned on with both 12 black
> >and white horizontal lines in the screen. No assembly prompt, Integer /
> >AppleSoft BASIC prompts are shown. I tried to hold and press CTRL-B keys
to
> >return to Integer BASIC from Old Monitor Routines, but nothing is
working.
>
> You must first press RESET.
Are you saying that I press and hold Reset key before turn on Apple II's
power supply?
> > Is it true that AutoStart Monitor Routine and Old Monitor Routine
zeroes
> >"FF FF FF FF" in each even page and "00 00 00 00" in each old page?
Or...Is
> >it the way how RAM chip zeroes "FF FF FF FF" and "00 00 00 00" in both
> >even/odd pages before power is turned on? It is impossible to show
garbage
> >characters in each RAM chips. On unenhanced Apple //e has "FF FF FF FF"
and
> >"00 00 00 00" in both even/odd pages, but it NEVER has any garbage
> >characters unlike Apple II does. I don't know if it is true that it is
done
> >to z尻｢ by neither RAM chip or Monitor Routines.
>
> No, those are just the power-up states of the DRAM chips.
So you say that DRAM chips zero "FF FF FF FF" and "00 00 00 00" in both
even/odd pages?
--
Bryan Parkoff
Wayne Stewart
> I already told him that if he is seeing the checkerboard
> pattern that the cpu is not getting power. It is the same
> on all Apple IIs. Take out your cpu and turn it on. You'll
> see what he is getting.
It isn't the same on all Apple IIs. You're describing what happens
in an autostart machine. With my non autostart machines the only
difference between what I get on screen is that when the processor
is present I get a the monitor prompt at the bottom of that
checkerboard pattern
Wayne
Bill Garber
"Wayne Stewart" <way...@telus.dotnet> wrote in message
Well, I can't really check what the non-autostart
ROM does, I only have autostart machines, and a ROM
card. Would it do that with the ROM card and no CPU?
Bill @ GarberStreet Enterprizez };-)
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Wayne Stewart
> Well, I can't really check what the non-autostart
> ROM does, I only have autostart machines, and a ROM
> card. Would it do that with the ROM card and no CPU?
With the ROMcard the Apple II will use the ROMs on the card instead
of the ROMs on the motherboard. Provided of course that the switch
is flipped. So if the ROMcard has the nonautostart ROM (3410004-00)
then it'll go to the monitor instead of into basic. If you want to
use the F8 on the ROMcard then the solder pads marked F8 should be
bridged.
If you use a ROMcard containing a non autostart F8 then the screen
will look pretty much the same with or without a CPU on powerup
Wayne
Michael J. Mahon
>> > I turned on Apple II Minus before HGR is turned on with both 12 black
>> >and white horizontal lines in the screen. No assembly prompt, Integer /
>> >AppleSoft BASIC prompts are shown. I tried to hold and press CTRL-B keys
to
>> >return to Integer BASIC from Old Monitor Routines, but nothing is working.
>>
>> You must first press RESET.
> Are you saying that I press and hold Reset key before turn on Apple II's
>power supply?
No, I'm saying that after you turn on the power, you must manually
reset the machine before pressing crtl-B <return>. (Depending on the
keyboard type/setting, this may mean simply pressing the RESET key
or holding Ctrl and pressing the RESET key.)
>> > Is it true that AutoStart Monitor Routine and Old Monitor Routine
>zeroes
>> >"FF FF FF FF" in each even page and "00 00 00 00" in each old page?
>Or...Is
>> >it the way how RAM chip zeroes "FF FF FF FF" and "00 00 00 00" in both
>> >even/odd pages before power is turned on? It is impossible to show
>garbage
>> >characters in each RAM chips. On unenhanced Apple //e has "FF FF FF FF"
>and
>> >"00 00 00 00" in both even/odd pages, but it NEVER has any garbage
>> >characters unlike Apple II does. I don't know if it is true that it is
>done
>> >to z K¢ by neither RAM chip or Monitor Routines.
>>
>> No, those are just the power-up states of the DRAM chips.
> So you say that DRAM chips zero "FF FF FF FF" and "00 00 00 00" in both
>even/odd pages?
Yes.
The Apple Monitor routines _never_ touched memory except incidentally
(some zero page locations and the text screen) until the //e, which tromps
on a couple of bytes per page on a reset to make capturing single-load
games more difficult. ;-)
Bill Garber
"Wayne Stewart" <way...@telus.dotnet> wrote in message
So, therefore, if Bryan is starting up and
no monitor prompt comes up on RESET, then
the CPU is probably at fault, but since it
works in another board, then the fault is
a trace on the 5v line somewhere. This is
provided the RESET key is working at all.
I wonder now if he has tested the keyboard
on another motherboard.
Michael J. Mahon
>"Wayne Stewart" <way...@telus.dotnet> wrote in message
>news:MPV%b.23987$A12.3961@edtnps84...
>: Bill Garber wrote:
>:
>: > I already told him that if he is seeing the checkerboard
>: > pattern that the cpu is not getting power. It is the same
>: > on all Apple IIs. Take out your cpu and turn it on. You'll
>: > see what he is getting.
>:
>: It isn't the same on all Apple IIs. You're describing what
>happens
>: in an autostart machine. With my non autostart machines the
>only
>: difference between what I get on screen is that when the
>processor
>: is present I get a the monitor prompt at the bottom of that
>: checkerboard pattern
>
>Well, I can't really check what the non-autostart
>ROM does, I only have autostart machines, and a ROM
>card. Would it do that with the ROM card and no CPU?
The Autostart ROM, and all subsequent Apple II ROMs,
clear the text screen before "signing on" for a power-on or
cold reset.
The non-Autostart ROM does not initialize the text screen,
but simply enters the monitor upon RESET. Before a RESET,
the state of the text screen is however the DRAMs powered
up. After a RESET, the screen is changed only by the
writing of the monitor prompt.
If, for some reason, the CPU does not reset, or does not
run the ROM code, then all Apple II's will display the power-up
state of the text screen DRAMs.
So, an original Apple II's screen after power up looks pretty
much the way _any_ Apple's screen will look if the processor
does not run the ROM cold reset code.
Michael J. Mahon
All it means is that the processor is, for some reason, not running
the reset code.
This could be caused by many things, since a normal reset requires
that page zero RAM and the text page RAM (plus its decoders and
buffers) must be working, the F8 ROM (plus its decoders) must be
working, the processor must be working, and reset must be working.
In short, if an Apple II resets properly, then all but the video refresh
and the I/O decoding are pretty well shown to be working. (And if you
can see the screen, the video refresh is working. ;-)
Since the processor chip is known to be working, a static check
of its power and ground connections is in order, followed by a
check of its receipt of the reset signal, followed by checks of
the memory buffers/transceivers and the decode logic. The failure
of any address or data wire or buffer or a chip select line will
effectively prevent the processor from running the reset code.
A simple check for a fault in the reset line is momentarily grounding
the /RESET pin of the 6502. This cannot harm the system, and if
it causes it to reset successfully, then the fault is isolated to the
reset signal.
Since the chips have been replaced without alteration of the symptoms,
the sockets, solder joints, and traces of the main board are called
into question, as well as any chips which have not been swapped
(like the F8 ROM, for example).
Bryan Parkoff
> So, therefore, if Bryan is starting up and
> no monitor prompt comes up on RESET, then
> the CPU is probably at fault, but since it
> works in another board, then the fault is
> a trace on the 5v line somewhere. This is
> provided the RESET key is working at all.
> I wonder now if he has tested the keyboard
> on another motherboard.
motherboard. They are functioning fine.
I give you an example. GR and HGR are not working on second motherboard
while Old Monitor Routine is not powered up on first motherboard. I tried
to swap ALL 74xxxx and DRAM chips from working motherboard to both defective
motherboards. The status is still the same. There is no solution for Old
Monitor Routine Start-Up and GR & HGR working.
I must admit that it is necessary for me to purchase electronic
diagnostic equipment to test three defective motherboards. I still have
voltimeter. Is it worth to obtain several different diagnostic tools?
--
Bryan Parkoff
Vince Briel
ground to pin 40 of the CPU. This is exactly more or less what the reset key
does.
--
Replica I
The Apple I clone
http://www.applefritter.com/apple1/members/replica1/index.htm
"Bryan Parkoff" <bryan.nosp...@nospam.com> wrote in message
news:aq30c.16730$OH4....@fe2.texas.rr.com...
Michael J. Mahon
> I give you an example. GR and HGR are not working on second motherboard
>while Old Monitor Routine is not powered up on first motherboard. I tried
>to swap ALL 74xxxx and DRAM chips from working motherboard to both defective
>motherboards. The status is still the same. There is no solution for Old
>Monitor Routine Start-Up and GR & HGR working.
If you have properly switched the chips with a working main board
and the fault did not "follow the chips", then you have demonstrated
that the chips are OK and are not the problem.
The problem is in what was _not_ different in the non-functioning
system--the main board.
> I must admit that it is necessary for me to purchase electronic
>diagnostic equipment to test three defective motherboards. I still have
>voltimeter. Is it worth to obtain several different diagnostic tools?
Hardware "diagnostic tools" are needed to diagnose hardware
problems that make the system incapable of running software
diagnostics.
I assume that you already have a Volt-Ohm-Milliammeter,
preferably with an audible continuity test capability.
If you know your way around digital circuits, I'd suggest at least
a logic probe and a logic pulser. An oscilloscope is essential for
more advanced work.
Since many board problems are mechanical in origin, I'd also
suggest a good light and a magnifying lens. For temperature-
related problems (not so common on an Apple main board) some
canned "freeze spray" is a good investment.
And, of course, a good, temperature-controlled soldering iron
with a clean damp sponge, some good fluxed solder wick, and
some small-guage rosin core 60/40 (or 63/37) solder is essential
to make repairs once you've found the problem.
Eric Smith
> I would like to know Apple II Minus history that it is the earliest
> model that it starts with Old Monitor Routines rather than AutoStart
> Routines.
There isn't a model called an "Apple II Minus". The earliest machine in
the family is the "Apple ][".
> Do white horizontal block like GR (low resolution) appears in the
> screen? Or...Do white horizontal block like TEXT ("@@@@" and "??????")
> appears in the screen?
It's usually somewhat random text, although graphics is also possible.
I say "somewhat" random, because on any given machine the display at
power-up varies a little but is strongly biased toward a particular pattern,
determined by the most probably power-up state of the DRAM. Each bit in
each DRAM has a tendency to power up in a particular state, but won't do
so 100% consistently.
> If it is GR, must you always press RESET before it returns to "*"
> prompt?
You must press RESET before you can do much of anything. This is why
they added an automatic power-on reset on later models.
> Sometimes, "???>@.?1??<??" show. Do you suspect that it may be bad RAM?
> Or it may be static leakage?
No, that's just the way it is.
> Are all "00 00 00 00 00 00 00 00" store in odd pages between $0000 and
> $BFFF and "FF FF FF FF FF FF FF FF" store in even pages between $0000 and
> $BFFF? If each page do show like "01 01 01 01", "7F 7F 7F 7F", "E1 E1 E1
> E1", "FE FE FE FE", or etc. I claim that all static RAM chips are bad.
There are no static RAM chips in an Apple ][. Nor in an Apple ][+. There
are only dynamic RAM chips. The power-on state of dynamic RAM chips is
undefined, so the fact that you get patterns does not mean that the RAM
is bad.
> I bought all 7xxxx chips and RAM chips from electronic store. I removed
> all old chips out of all sockets. I threw them in the trash. I put new
> 7xxxx chips and RAM chips in all sockets. I did test, but the result is
> still the SAME. Such as GR and HGR are not working (never turn on, but stay
> in TEXT only).
Why did you throw away the old chips? Most of them were probably fine.
The first thing I would have suspected with a problem like that would be
the 9334 or 74LS259 chip that implements the "soft switches". Since you
apparently replaced that without fixing the problem, the next thing that
comes to mind would be the address multiplexers that take the video counter
outputs and produce the DRAM row/column address. But if you've replaced
those too, I start to wonder if one of the contacts of a socket might
be bad.
> Probably some resistors, capicators, and other electronic parts are bad
> however all chips are working fine on another Apple II+ motherboard.
Although I won't claim that it's impossible, it seems somewhat unlikely
that a passive component failure would cause the symptom you describe.
> Please suggest which electronic diagnostic tools that is very worth for
> me to buy before I can be able to isoslate defective parts. If I have found
> defective, I would be ABLE to repair. Please advise.
The most important electronic diagnostic tool is your brain. You need to
understand the design, come up with a hypothesis as to what might cause the
observed behavior, and a plan to test the hypothesis. All the fancy
electronic diagnostic tools in the world are just a waste of money if you
can't do that.
Throwing away all the chips and replacing them with new ones is a "shotgun"
approach suggests that you are not very serious about troubleshooting the
machine.
However, if you ARE serious about it, what you probably need is an
oscilliscope with at least 20 MHz bandwidth. That will allow you to
examine waveforms of signals. However, it will require you to figure
out what signals to examine, and what the waveforms should be.
A logic analyzer is another tool that would be useful. Generally they
cost more money than oscilliscopes. Logic analyzers are great for
debugging digital problems, but if you need to determine analog signal
levels or waveforms they won't help. (Unless they're really high-end
ones that have integrated oscilliscope functionality.) There are,
however, some inexpensive limited-function logic analyzers for PCs, such
as the ones from http://www.usbee.com/
If I had very limited money to spend on such things, I'd probably try
to buy a used Tektronix 465 oscilliscope. That's a two-channel 100 MHz
analog scope with all of the basic features you need. They were very
expensive in their day (late 1970s), but can usually be found for under
$250 now.
Eric Smith
> So you say that DRAM chips zero "FF FF FF FF" and "00 00 00 00" in both
> even/odd pages?
It varies depending on the manufacturer, part number, and sometimes even the
individual part. DRAMs don't have a defined power-up state, so it depends
on the internal topology of the array, how the cells are mapped, which
sense amplifiers are inverting vs. non-inverting, and various other
characteristics.
Michael Black
> "Bryan Parkoff" <bryan.nosp...@nospam.com> writes:
>> I would like to know Apple II Minus history that it is the earliest
>> model that it starts with Old Monitor Routines rather than AutoStart
>> Routines.
>
> There isn't a model called an "Apple II Minus". The earliest machine in
> the family is the "Apple ][".
>
which of course wouldn't have been called "Apple I" until there was a II.
After all, "Plus" suggests better than the Apple II, so "minus" suggests
something lesser than the Apple II. The only thing lesser from Apple
was the original Apple.
Michael
Michael J. Mahon
<snip>
>If I had very limited money to spend on such things, I'd probably try
>to buy a used Tektronix 465 oscilliscope. That's a two-channel 100 MHz
>analog scope with all of the basic features you need. They were very
>expensive in their day (late 1970s), but can usually be found for under
>$250 now.
I second that. I found one for $200 in a local store about two years
ago, and I use it all the time.
They often go even cheaper on eBay, but then there's shipping
and uncertain calibration and condition...