7 Dec
2010
7 Dec
'10
9:48 a.m.
Hi Tony and others. Progress and pin readings from the Lisa 2 project...
I've cleaned a couple of the 400k Drives thouroughly just in case the
machine was struggling with the mechanisms. No change. The drives still
sit there on boot in stubborn silence, although the LEDs inside are lit. No
sound or attempt at disk ejection when there is a disk present.
I did some measurements on the Lisa Lite board input connector, and here's
what I found. I used the circuit diagram at
http://www.freeinfosociety.com/electronics/schemview.php?id=1417 . The
signals in brackets represent the corresponding pins on the sony floppy
drive. A disk was in the drive at the time.
PH0 (CA0) - 0.2v but rises to 3.5v momentarily when the machine is first
switched on
PH1 (CA1) - 0,2v normally but every 4-5 seconds this pulses to 3.5v
PH2 (CA2) - Same as PH1
PH3 (LSTRB) - 0.2v
WRQ (WRTGATE) - 4.9v
HDS (SEL) - 4.3v but pulses to 0.2 v every 4-5 seconds
DEN (ENBL) - 0.2v
RDA (RD) - 4.9v but pulses to 0.2 v every 4-5 seconds
WRD (WRTDATA) - 0.2v
MT (goes to Lite Adaptor circuitry) - 0.11 Returns to drive pin as PWR -
3.6v
All 12v and 5v power and ground pins read what they should.
SNS - 4.9v but pulses to 0.2 v every 4-5 seconds
I''m still digesting what this all means using the Lisa hardware manual here
http://lisa.sunder.net/LisaHardwareManual1983.pdf . There is a
comprehensive explanation of how the drive interface works in section 6 but
I'm still digesting this and trying to get my head around it. Appreciate
that I'm not a techie and a lot of this stuff is new to me.
As I see it at the moment, the drive is certainly getting power, and appears
to be getting signals. Whether these signals are the right ones are another
question?
Terry (Tez)
----- Original Message -----
From: "Tony Duell" <ard at p850ug1.demon.co.uk>
To: <cctalk at classiccmp.org>
Sent: Monday, December 06, 2010 10:09 AM
Subject: Re: apple Lisa2. Any advice on non-working floppy drives?
Can you? I have no idea what these startup checks actually test, but I
would have thouht it as possible for one of the I/O chips that links to
the drive to havee failed but in a way that it still passes the tests.
>
> Tony, thanks for doing that bit of research.
......
......
I have a
manual with some schematics and tonight I'll check and see if
the
LisaLite board is there.
As I said a Google search found it fairly easily. The Lisalite board
looks quite simple (the schematic is just 1 sheet, and I recognisd all
the chips on it). I didn't do much more than glance at the schematic, but
it seemed to be a dairly simple PWM generator using TTL coutners and '85
comparators. I think the control vaule is bit-serially loaded into a
shift register on the board.
Firstly, since you have no idea as to the health
of any
of the parts, you can't deduce anything from the fact that swapping
them
out makes no difference.
Not entirely true, as the Lisa 2 startup checks carry right through until
it
asks for a disk for inserted. So I can assume most parts are working. Incidently, the docs I have suggests this routine
also checks the
LisaLite
controllers so (according to the machine anyway) these are ok. It's hard
to
I wonder how? I couldn't see any way for the machine ot check that the
PWM signal (the only signal truely sourced by the Lisalite board) is
present and corret.
believe that THREE drives all have the same fault
though. All inputs
into
the drive are from the LisaLite board. Maybe the diagnostic checks are
not
Not really. While the only external cable from the drive does, indeed,
plug into the Lisalite board, the shcmeatics show the most of the signals
are simply passed (with no buffering or anything) between the 'Twiggy'
connector back to the Lisa I/O board and the Sony drive connector. I
think it's likely that any problems iwth those signals are not caused by
the Lisalite board (broekn PCB tracks are not common).
as thourough as they should be.
We don;t (or at least I don;t know) what hte diagnostics actually check.
There's also the issue that you're using a defective system to diagnose
itseld, and while most diagnostics are written assuming that anythign
that hasn't been checked could well be defective, some are not. I've seen
diagnostics that basically assume that the machine is working correctly,
and which don't help _at all_ if there is a fault.
I really do think you need to start making some measurements on the drive
connecotr and see just what is, and is not, correct there.
-tony