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Re: Dead //c

Vincent Quinn <gospodin@indigo.ie> wrote:

> I have an Apple //c [... which] was working fine until around ten days
> ago. Then it died mid-way through a disk access.

[description deleted]

> OK - by a process of elimination, I suspect that the internal power
> converter is dead. Am I right? Does anyone have any other diagnoses?

The most likely candidate is the IWM disk controller chip, or some
associated component.  It might also be something as simple as a
corroded track or dry solder joint.

As far as the power converter is concerned:

The internal power converter only generates three voltages: +5V (which
must be working, or the computer would be totally dead), +12V (used
mainly for powering the disk drives) and -12V.  There is also a
regulator which generates -5V from the -12V rail.

Do the drive motors spin?  (This should be most noticeable on the 5.25"
drive.)  If so, the +12V rail is probably OK.  

The -5V and -12V rails are used by the video and keyboard circuitry, so
they are probably OK.  The serial ports use +12V and -12V, so if you can
send and receive (using the built-in terminal mode, for example) then
both rails are probably OK.

The disk drive is provided with +5V, +12V and -12V.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand