Trouble with Apple //e & Unidisk 3.5 & 4mhz. ZIP chip

[ehillman@erinet.com (Ed Hillman)]

I have recently gotten interested in my Apple //e extended keyboard
(enhanced) which has been in storage for 5-6 years. It is configured
as follows:

Slot 0 - AE Ramworks III
Slot 1 - Tymac printer card
Slot 2 - Apple Super Serial Card
Slot 3 - Videx Ultraterm
Slot 4 - Microsoft Softcard (Z-80)
Slot 5 - Apple Unidisk 3.5
Slot 6 - Apple Duodisk
Slot 7 - Sider 10meg Hard Drive

No-Slot clock under ROM on Sider interface card.

I set it up and all worked fine. I upgraded to ProDOS 2.0.3 and the
latest No-Slot Clock ".sys" driver and all worked well. (Not having
the NSC patch file for ProDOS 2.0.3.)

Last night I re-installed my 4mhz ZipChip and all seemed to work OK,
though I didn't do a through check-out.

Tonight I performed the capacitor removing mod on the Duodisk analog
board to avoid the disk trashing problem I read about in the FAQ's on
this newsgroup. 

All seemed OK, until I tried to use my Unidisk 3.5. It would try to
read and write, but would mostly just lock up the machine requiring a
reboot. I started backtraking my changes to see what caused the
problem. First I made sure the ZipChip was set to slow speed on Slot
5. It was. Then I tried disabling the Zip in software. Still no good.

Then I completely removed the Duodisk frm the machine and still the
Unidisk 3.5 wouldn't work properly.

Finally, I replaced the Zip with the original 65C02 CPU and the
Unidisk started working again. Reinstalled the Dudisk and all was
still OK.

Evidently the ZipChip, even disabled will not allow the Unidisk to
operate. 

I don't remember there being a conflict between the Zip and Unidisk,
but then for some reason I had pulled the Zip prior to putting the
machine in storage. (My memory doesn't work back that far... I've
unfortuantely hit 50 years old!)

Does anyone know of any such Unidisk/Zip conflict and any possible
workarounds?

Thanks for any info,

Ed