Re: IIgs MB repair info

["Bill Garber" <willy46pa@comcast.net>]

> If I remember correctly (and that's a *big* if), the drives are supposed
to
> start the spin-up cycle as soon as power is applied, whether or not the
> motherboard starts talking.  The 'grunt' from the drive sounds like one of
> the voltage lines from the power supply is no good.

Hoped everyone would realize power supply has already been ruled out.

> That could either be due to a bad power supply or a short on the board.  I
> would suggest:
> 1) bench the power supply and check the voltage of each power line while
> driving a test load
> 2) remove any peripheral cards in case one is misaligned
> 3) also disconnect any 'unnecessary' peripherals in case, for example,
> somebody mis-indexed a pin when the drives were plugged
> and if that doesn't turn anything up:
> 4) try a different power supply.

Running a bare board with drive on smart port, no cards, power supply
is known good. Short on the board is suspected, hoped someone would
have an idea which area on the board to zero in on.

> The most likely failure modes:
> #1:  90% - something is misaligned such as a Disk II cable connection or a
> socketed chip
> #2:  9% - bad power supply
> #3:  1% - failure of one of the unsocketed chips (expressly assuming that
> all socketed chips are 100%)
>
> Problem #3 is far more likely to occur in combination with #1 than by
> itself.

Yes, I assume the same is most likely. Anyone with an idea which
area to pinpoint would help tremendously. Of course at $5-$20 for
a IIgs CPU with PS, it may be time to just dump this one and get a
replacement. I like to mess with them though.

> Post-infancy chip failure usually does not occur unless induced by an
> electrical short circuit.  I've seen #3 occur only twice, once when
somebody
> was hot-plugging peripheral cards on the bus and once when a defective
> peripheral cable shorted the power supply.

I agree, there definitely was some careless activity going on here, not by
me, this GS came to me this way. ;-)
Thanks.

Bill @ GarberStreet Enterprises };-)
Web Site - http://garberstreet.netfirms.com
Email - willy46pa@comcast.net



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