Re: Apple floppy adaptor. A little update

[Tristan Mumford <xtristan.xmumford@xgmail.xcom>]

G'day!

Today I had a feeling, which I acted upon. I wondered if the little short
the adaptor board had didn't cause more damage than I thought. It seems it
may well have.

Just to find out, the Atlas 8 was plugged in to do a few tests. It can read
perfectly, as expected. However trying to format a disk results in the same
failure to write I have been seeing.

Based on the assumption* that the short was from -12v to WREQ I traced the
lines to what seems to be an open-collector 74LS06 (M53206P) on the
controller.

Holding my amazing LED and resistor logic probe on the WREQ line and
attempting to perform a write (ProDOS format) results in no difference in
the logic high state.

Does anybody know better than me about the nature of the IC? I'm just making
an educated guess based upon the functionality of a proper disk][ and the
look of the part number on the IC.

At least it only seems to be one dead pin. Now to figure out how to desolder
the chip without destroying everything. It's going to get a nice machined
pin IC socket I think :)

All in all a bit of a shame, as I believe I may have the adaptor correct
enough for it to work.
I found a better hex inverter and plugged it in. It now proudly displays
its "16 SECTOR" message as soon as it reads the disk.

One odd thing to note is the IC in question doesn't seem to have any
continuity between +5 and the signal line (when not powered) as I would
have thought for this problem.

Tristan.

* Visually it looked like a solderbridge was between WREQ and -12v. Also
that was where I had just done an alteration to add a line to monitor WREQ
to know when to use the disk writing code in the uC. So it seems logical
that this was the issue.