General Category > Lisa Troubleshooting and Repair
Restoration of a Lisa 1
snuci:
--- Quote from: stepleton on May 09, 2020, 07:13:09 pm ---As a check, just after booting, do you hear the Twiggy drives "grunt" as they activate the ejection mechanism in either drive? At least, this is what happens on my Lisa 1. The ejection mechanism is also activated when I shut the Lisa back down.
--- End quote ---
I did make one disk which I think should be okay but I am not sure if it is functionally okay. To make the disk, I cut the plastic melted plastic "rivets" on one side of the floppy diskette and unfolded the left side flap of the diskette; taking out the cookie. I then cut the appropriate holes and put it back and glued the flap back into place. Structurally, it should be okay but I am not 100% sure the cookie was unscathed. My top drive acts like the video I am pointing to below. Inserting the disk for the first time does it's initial checking. You will hear a click in the background (that's the mouse button I clicked loudly) and then the disk was attempted to be initialized. That didn't work so I ejected it. The bottom drive doesn't move properly but I will investigate.
http://www.vintagecomputer.ca/files/Apple/Lisa/Testing/Twiggy.mp4
Is this normal or abnormal for the top drive? I checked an online video by Alker33 and it is different but he also had a known good disk so is my head movement normal for a bad disk?
Thanks for any help.
stepleton:
The video sounds normal until the heads assume that central position and do that "chunka chunka chunka chunka" thing. That's nothing I've seen before.
It's interesting also to see that the "chunkas" didn't happen when you tried the initialisation---but the heads still refused to retract any further than they do.
And yet, the heads clearly can retract fully when it comes time to unclamp and eject the disk, so it's not like there's a mechanical blocker. I don't have a lot of Twiggy repair experience, but I can't think of an obvious reason for the drive to refuse to retract the heads during ordinary seeks like yours does. There's a sensor that tells the head carriage when it has been fully extended (look for the red, brown, and orange wires feeding into it at bottom-right of this photo), but there's no separate sensor to detect full retraction that I know of.
(My guess is that the head positioning is calibrated by the full-extension sensor, and then the disk drive controller just counts stepper motor "steps" after that. It seems unlikely to me that the stepper motor would still step but that its counting would go off, so I don't think it would be a problem with the computer losing track of where the heads are.)
Maybe it's what's on the media. Would it be possible to try formatting the disk in BLU? Perhaps the Office System is expecting an uninitialised disk to have been "more formatted" than yours is.
PS: Kudos on the precision of your cutout for the near head---it looks very nice!
snuci:
Okay so I booted from the X/Profile/BLU and tried to format a floppy.
Upper drive: "Floppy drive error 1B" after some trying. When I pressed "F" to fail, I got "Operation Failed Error Code FA20"
Lower drive: still doesn't clamp down. Got an error 16 on that one.
Is there list of error codes and what they mean?
stepleton:
While I don't know what FA20 means, the other two codes are described on page 6-37 (PDF page 206) of the Lisa Hardware Manual.
$16 is "Unable to Clamp", so nothing too newsworthy there.
$1B is "Unable to Adjust Speed".
As you probably know, Twiggy disks spin at different speeds depending on which track is being accessed. I guess this is why your heads refused to retract any further---they were supposed to change speeds once the heads passed a certain point, but they didn't. I don't know too much about how this is controlled, so an error like that for me would be the beginning of a schematics-n-probe adventure, I expect.
Perhaps first check the easy stuff. On your Twiggy drives... are all the connectors plugged in? Are all the chips well-seated in their sockets? Here are a pair of pictures of one of my drives to compare against:
https://photos.app.goo.gl/63moQ338i9PWuFUx6
Speaking of schematics, none of the Twiggy schematics I've seen online match my drives very well. This set on Ray's site is the same as the one on Bitsavers, and there are some big differences---for example, page 3 says that an MC3470-E5 read amplifier chip should be present somewhere, but there's nothing like that on my drives.
(I see you're getting some information over on Facebook---I'll tune in there, too and see what they come up with...)
snuci:
I meant to post my pictures here too. Here are my boards. I will double check all of the connections and even test the components. I can hear at least three distinct speeds when the upper drive tries to read the outer track. Kinda cool but I don't think it finds the right speed so something.
http://vintagecomputer.ca/twiggy-pics/
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