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Re: Apple II Minus Question

Bryan Parkoff wrote:

    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.  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.


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