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Re: Apple //c, 255 version: rare?



On 8/5/2010 11:03 PM, The Elfe wrote:
"Michael J. Mahon"<mjmahon@aol.com>  wrote in
g7-dndafytxF98bRnZ2dnUVZ_rmdnZ2d@giganews.com:">news:g7-dndafytxF98bRnZ2dnUVZ_rmdnZ2d@giganews.com:

On 8/5/2010 9:23 AM, The Elfe wrote:
Mitchell Spector<mitch2gs@hotmail.com>   wrote in
lk6k569vb7hjf7e35410crf0c48jlhdkcp@4ax.com:">news:lk6k569vb7hjf7e35410crf0c48jlhdkcp@4ax.com:

The Elfe<email@nospam.com>   wrote:

      Less common to find, at least in my experience, is the original
      IIc
motherboard with serial port timing glitch (identified by the
presence of a 72LS161 chip rather than a tin oscillator). Also less
common is a IIc with the 'ROM 4' firmware. Or better yet, 'ROM 5',
which is the IIc Plus. :) None of these are rare per say, just less
common.

I'm living in Europe.
Mine has 2 problems: one is when I press CONTROL+RESET, I could
nothing type, for the cursor was moving endless
>from time to time with some strange patterns and some beeps. Well I
have
to find another motherboard, I think, aye.

      Sounds like certain keys are stuck, either physically or due to
the fault of failed circuit logic, like the keyboard encoder chip.

      The original ROM (255) had no built-in self test diagnostic,
however if you pressed Apple + Control + Solid-Apple you'd
get something like you describe. Could be the Solid-Apple
key is stuck, or shorted because of an attached joystick.

      Could also be bad DRAM's on the motherboard, though
the only way to tell is to run a floppy disk based diagnostic.
I'd recommend the Apple II Diagnostic from Apple.

Mitchell Spector

Well, the original ROM (255) has a "almost"built-in self test
diagnostic... but neverending. I know that I can start the
diagnostic, stop the working disk drive. So it could be a bad ram or
keyboard encoder chip. is there a means to check this chip?

Thank for your help,
The Elfe

First, I'd make sure that there isn't a keyboard keyswitch that's
stuck.

-michael

Well, I tried with another working keyboard. What would happen if I
remove the keyboard chip, then switch on the Apple 2c?

If the encoder is the problem, that should make the machine boot
normally.

-michael

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