Re: UNIDISK 3.5 800K DRIVE: metal shield

[supertimer@aol.com (Supertimer)]

buggie@ben07.unm.edu (stephen e buggie) wrote:

>       I have successfully repaired the 65C02 processor chip in two
>Unidisk 3.5" drives!  They were junk before, but now they WORK!
>
>But I added a socket for the 40-pin processor, and this increases the
>vertical height to such an extent that the metal shielding wont fit.
>The drive casings are held together now by DUCT TAPE ---- looks bad, but
>works okay.
>
>Am considering for the next repair on a Unidisk 3.5, to cut the center out
>of the metal shielding cap, so that the case can be reassembled with the
>corner screws being used --- eliminating the duct tape.
>
>But is the metal shielding very vital?   The drive works fine when
>operated as a naked unit outside the housing.   How serious is RF
>interference on radios in the house???

Dr. Buggie, I've removed metal shielding from Apple brand
devices before to no ill effect.  The thing about today's
electronic devices is that they are all shielded.  So unless
you remove the shielding from TWO of your computers,
they won't likely interfere.  The second thing about the
shielding is that it is grounded but since the voltages are
low and the case is plastic, there is very little danger to
the user or the device itself.

If some of your Unidisk 3.5s can't be repaired in this way,
I suggest bypassing the internal 65C02 completely and
turning them into standard Apple 3.5 IIGS daisychain
drives that work on both the IIGS and Mac.  See below:

http://ground.ecn.uiowa.edu/apple2/MiscInfo/Drives/unidisk35.labotomy

By the way, your post about failing 65C02s in Unidisk
3.5s and the seeming increasing failures of 65C816
chips in early TransWarp GS units indicates that the
CPUs may be failing due to age.  This has been fairly
well documented in the PC world, where the average life
expectancy of a chip is 10 years.  It is usage (electricity
going through the chip) that causes the electromigration
that eventually causes the chip to fail.

This is not saying that there won't be chips that last a
lot longer.  The less a chip is used, the longer it will run.
But those units turned on 7 days/24 hours better watch
out!