Swapping your Drives on a Disk ][ Controller

Hello MarkO,
nice gimmick.....
today i´m out of home, but in the evening i´ll draw the plan and circuit and publish it here.
of course i guess you know the answer by just flipping the interface...
so it´s at least like a crosswordgame in the sunday magazin.... - but the mod is rather simple....

in short words: its a flip by switch of the pin 14 at both cable connectors by cut of signals from pin 8 and pin 6
at the 74LS132 in position A2 ( in the circuitplan ENABLE1 and ENABLE2 )....

but for the other members i´ll publish a scetch this evening....
speedyG

Update: here is the drawing:

This is also the reason for the extra "spare-cable at the 20pin to 19DB Adapter used to connect new "daisy chained"
drives to old DiskIIcontrollers ( but recognize the adapter only works with maximum of 2 drives ! )

see below:

was that the answer you expected Mark ?
sincerely
speedyG

In Amstrad world, this is called the ABBA switch. Here's a link to the document that explains the principle.

In Amstrad world, this is called the ABBA switch.

Oh, thanks for that. Now I've got that song in my head.

Hello Mark,
"Master" is too much.... rather better "the dinosaur".....
your allways welcome in the dinosaur cage...
( just a joke reminding to a cartoon in the book "beneath Apple Dos"
displaying the dungeons for the assembler programmers in chapter 6 page 1 .... LOL )
speedyG

Thank you very much for posting that. I'll give it a try as soon as I get the parts and time!

can this be done on the iic? if so, please post it.

Hello Mr.Fix,
i have not inspected the IIc yet for a possible modification,
this modification is as explained above related to the DISK II controllercard in regular
Apple II series ( the thread started with a link to the picture of the card and the switch ).
If i understand you correct, your question is:
"is there a mod that permits switching between internal and external drive at the IIC as
startup drive - so the user can switch if he wants to boot from internal drive or external drive?"
is that correct ?
speedyG

Hello Mr.Fix,
allthough your reply to previous post is missing i have examined the circuitplans of the IIc.
By that examination i can reply: There is a chance of 98% to add such a mod to the IIc.
But due to the fact that i don´t have a IIc here in my place i would urgently need
2 very good closeup pictures of the related area with perfect lighting and perfect focus.
I have taken a snapshot from SAM´s repairmanual to explain the requested area
and i have marked up the specific area i need 2 or 3 closeup pictures by light red shading:

The 2 pictures must be one or 2 from the vertical top side ( population area ) and one
from the soldering side of the PCB. If i get links to such pictures i can examine
the PCB and make a description by use of that pictures. The pictures must be hires
( meaning that their resolution must be something approx. to 5000 x 4000 pixels ! )
to enable me to zoom in for details.

If you or any other member replies here with the link to such demanded pictures i can
add here such a mod description for the IIc.

sincerely speedyG

In Amstrad world, this is called the ABBA switch.

Oh, thanks for that. Now I've got that song in my head.

What song?????

UPDATE: There are quite large differences between the different IIC models.
Therefor it would be usefull to get the demanded 3 pictures from each Model:
the IIc and the IIc ROM4

I´ve got rather good pictures in the meantime from the IIc Plus so i´ll start on those
pictures first.

First a picture of rearside of the IIC to ensure same numbering of the output pins at the diskport
according to the numbering at SAMs documentation:

resulting from that pictures i´ve been following the relevant traces at the solderside:

and then also following traces at the topside and adding virtualy partially the traces
found at the solderingside and markung the important point with Alphabet or Numbers:

and the using the notation of the picture above added to the shematic from SAMs
and adding the wiring instruction to the switch in the picture below :

Note: DR2 signal is signal of second external drive while Int/Ext is used for
first external drive and DR1 is used for internal drive !

sincerely
speedyG

SpeedyG: thanks for your quick assistance and procedure for the iic. Here are a couple of pictures of my Rom 3 iic. Basically your assumption is correct, using a toggle switch between the internal IDC20 connection and the DB19 connection which will make either one the primary boot drive at a flick of a switch.

http://e21.tricord.be/members/Misc/pic1.jpg
http://e21.tricord.be/members/Misc/pic2.jpg

Hello Mr.Fix,

according to your pictures of the regular IIc i´ve marked up the changes the exact
same way as in the pictures above so you may use the same explenations like in the
pictures above and the same wiring at the switch.

The only difference:
In the pictures above both mods are performed at the top side of the PCB and HERE
at this pictures the steps 3 and 5 and 6 are performed at the SOLDERING SIDE !
( recognize the second picture below is from that solderingside.

The Letters and numbers are same points like markings used in the picture and Circuitplan above.....

here the top:

and here the soldering side:

Remark: examining the circuitplan you will detect that Q1 and R19 has been deducted from
this later models and the INT / EXT signal is directed straight to the plug.
There might be a Q1 or R19 but not in use like in this circuitplan !

another remark:

there is still another model not explained yet, where below the IWM chip is only one logic chip
instead of the two logic chips besides eachother in this model.'
The mod at that model would request another set of pictures to be posted here.

sincerely speedyG