- The value at FCC051 is always different every time I try to read it, is that a good sign?
Yes and no... it probably means the 6504 is running and reading the EPROM correctly, which is good, but means you don't have a simple problem to solve.
plugged in an ESProfile emulator into the 26 pin port right next to the lite adapter board
That's an easy mistake to make. Back in the 80's we didn't have the plethora of inexpensive connectors available today, so it was more difficult to make all connectors unique (eg. the serial and parallel back panel connectors both using DB-25). However, having been made in those 'simpler' times, the Lisa is also much more repairable than modern computers.
The pinout of the Twiggy drive cable can be observed from the Twiggy Digital Board schematic that it once plugged into.
https://lisalist2.com/index.php/topic,524.msg3712.html#msg3712The pinout of the parallel port connector (that the ESProFile expects) is nicely presented in Patrick's IDEfile documents
http://john.ccac.rwth-aachen.de:8000/patrick/idefile.htmSince TTL is generally tolerant of misconnections between 0 and 5V, I'd guess the problem on the Lisa side was caused by the ground pins of the ESProFile shorting +12V to something. (You might find more issues beyond this.)
On the parallel port 26 pin header as used by a Widget, these pins are connected together for ground: 2,3,7,12,14,17,19,22,26 I don't know if all of them are used for ground by the ESProFile but for some other device they are likely to be, so we will consider them all.
On the Twiggy Digital Board Schematic, +12 is connected to pins 1,3,5,7.
In addition we have -5V on pin 25.
So plugging those devices together is likely to put +12V on what would normally be Widget ground pins (but are not ground for the floppy connector).
The pins suffering this potential injustice are:
2 - Phi A
12 - /WREQ
14 - RData
17 - -12V
19 - (n/c)
22 - MClk
26 - (n/c)
-12V is weak supply, but the circuit to the PSU may have been damaged, so first check that:
a) all the voltages from the PSU are within tolerance (measure at points on the I/O Board), and
b) +12 and -5 still make it to the end of the Twiggy connector ribbon cable
Tracing those signals to the I/O Board:
Phi A comes from the 8T97 U2F, which is used by the FDC to interrogate the floppy drive for disk-in-place, write protect, move the head etc. I imagine that if this were damaged, the FDC might hang trying to access the floppy, resulting in error 57.
/WREQ comes from U3F-10, but is only used for writing to the floppy, so maybe U3F is damaged; you may not find out until you try to write to a floppy.
RData goes to U5B-13. Again you may not find out if U5B is damaged until you try to read data from a floppy.
MClk is called MT0 or MT1 (depending on upper or lower drive cable) on the Motherboard and I/O Board schematics. These are driven by U4F. If the motor spindle doesn't run when the FDC tries to read or write to the disk, then U4F would be the suspect. It could be that only the upper drive output is damaged, in which case you may never know until you plug in a set of Twiggies.
On the Lite Adapter, Phi A and MClk go into U6F, so it may be damaged.
(There is the possibility that the connection was made with a connector backwards / 180 degrees around, so the notes above are assuming the connection was made in the normal orientation, not backwards. If the ESProFile header is polarized, that might ensure this.)
And there is the possibility that a high current opened a trace somewhere (like blowing a fuse); I think this is unlikely for this situation, but you could look around for a scorched trace and check the continuity of any suspects.
Starting with those possibilities, you could replace them all or if you have some test equipment, do some troubleshooting (eg. watch each signal with a voltmeter or oscilloscope to see if there is any activity) to determine which ones are still ok.
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Topic: Will the Lisa return an IO error without the "Lite" Interface Card (Read 14975 times)