Its been great watching the progress of this topic... I pulled out an
old photo of my room from I think 1989 when I owned a Lisa (aka Mac XL)
I think I know what you mean now. That TA 7259 is the
chip underneath
the large brown clip/cover at the front of the drive. I'm not sure
how to remove the latter though? I seems solidly glued in covering
the pins of the chip. If I could remove this, I could measure the
signals on these pins when I tap the switch (thereby fooling the drive
into thinking a disk is present).
Or do you need to remove the motor, switches, plugs and then slide the
motor PCB out towards the rear until it's clear of that clip/cover.
Thinking about it, that's probably what's needed. In that case, it
won't be so easy to test as everything will be in bits.
Terry
Now, there seem to be 3 ICs on the motor PCB,
same as the standard one.
tHe 2 SIL packages (black plastic strips with 9 pins in a row along the
bottom edge) are a dual op-amp and the speed control PLL. The modifed
DIL
package at the front labelled TA7259 is the motor controlelr I've been
mentioning. I hve checked, you can get a data sheet on that from
http://www.datasheetarchive.com//