Powerbook Duo 280c + Accessories Maintenance

[jmacz]

I got my hands on a few more Duo keyboards. Out of them, one was clearly "better" than the one I already had in that the keys were much softer (albeit still stiffer than I would like) and only one key had an issue ('Q') whereas the keyboard I already had had issues with the 'O', 'Delete', and 'Space' keys. The others I received were a bit stiffer.

Lubricating the keys made them a bit better. The Q key was resolved using a conductive pen (thanks @3lectr1cPPC for the idea).

Based on what I have read, these keyboards weren't great even when new. Having played with a few of these now (but still not a great sample set), I'm seeing the issues falling into the following categories:

• Having to hit keys dead center - seems like this was always the case with this keyboard design as it requires a conductive ring underneath a rubber dome to be pushed onto a two layer film where the conductive ring needs to contact a conductive pad on both films at the same time. Doesn't seem solvable.
• Stiff keys - primarily depends on how well the rubber dome layer has aged. Heating did not help.
• Stiff keys part 2 - lubricating the stems on the keycaps with plastic safe keyboard lubricant (grease) does help a bit. This also helped on my PowerBook 540c keyboard as well.
• Contact Oxidation - the two film layers have conductive pads and some of the pads I saw across the keyboards I had showed oxidation. Deoxit helps a bit here to clean the pads up.
• Dead key - if there's a ribbon tear/issue, multiple keys should not work and you'll need to check the ribbon cable for tears or check whether the ribbon cables are seated properly. But if you run into a single key not working, that's most likely caused by the conductive ring on the rubber dome not properly coming into contact with both pads on the films, and/or the pads being damaged. If the contact isn't great, you can try using a conductive pen (it 'draws' conductive ink) on the two pads. This fixed a stuck key for me.

Keyboard resolved... not sure what I'm going to do with all these spare keyboards...

 

[3lectr1cPPC]

I'm glad that you were able to get your keyboard fixed and working!

 

[A24A]

/.../

Based on what I have read, these keyboards weren't great even when new. /.../

Yes, keyboard problems were mentioned, for example, in the following 1994 FAQ:

https://websites.umich.edu/~archive/mac/util/powerbook/duofaq.txt

 

[jmacz]

Sanded and painted. Close, not exact, but willing to live with it. The stock battery cover I had was also discolored (yellowed) so that one didn't match either.



This one in person is slightly darker.

 

[jmacz]

Capacitors finally arrived and allowed me to recap the power supply. With the new caps, no more ticking noise. I was able to insert the Powerbook Duo and boot. External monitor, keyboard, floppy drive all seem to work fine. The ejection button also works.

Two problems I'm seeing however.

1.) Dock Icon on Boot - I get a duo dock icon on boot and it stalls there for like 10 seconds before then continuing to boot. Not sure if that's normal or not. Note that I have no SCSI hard disk inside the duo dock.

2.) Auto Inject of Duo Doesn't Work - with the lid off, I can see the latch attempting to pull the duo in but it fails to grab the duo. I have to push the duo in the rest of the way and then it works. I noticed a similar clamping problem with the mini dock I have so it's possible something is misaligned on the duo itself.

Unfortunately realized this dock didn't come with the key so it's going to permanently unlocked. Not sure if keys were coded to a particular dock or whether it's a generic key. No big deal.

 

[techknight]

Sanded and painted. Close, not exact, but willing to live with it. The stock battery cover I had was also discolored (yellowed) so that one didn't match either.

View attachment 84350

This one in person is slightly darker.

Do you have the model for that battery cover? Do you have a model for the internal housing like a blank?

Also theres a couple different versions of those doors. Older one has a longer button.

 

[techknight]

@finkmac modeled it... but need to try some test prints later to ensure the dimensions work. That said, going to be a pain to print due to the little diamond shaped standoffs inside it and getting the support structures in place.

View attachment 84204

These are reeeeeeealy hard to print. Someone shared a model of this one on Discord, and its slightly off. But, trying to print this on a P1S is proving a bit tough.

 

[jmacz]

Do you have the model for that battery cover? Do you have a model for the internal housing like a blank?

Also theres a couple different versions of those doors. Older one has a longer button.

Yup, it's on my printables (link in my signature). I only have the model for the door that I have which has the smaller button.

 

[jmacz]

These are reeeeeeealy hard to print. Someone shared a model of this one on Discord, and its slightly off. But, trying to print this on a P1S is proving a bit tough.

The model I made should be pretty close. I tested fitted it and it worked well. I used tree style supports (and only from the base plate) and that seemed to work ok. The printer I have is pretty good (Qidi Plus 4) so the supports came off easily and did their job. But yeah, this isn't an easy print.

 

[jmacz]

My Duo Dock issue is resolved... I took apart my Duo and was watching the mechanism and noticed the clips would not stay down... they would drop down to hook the Duo but then immediately spring back up.

As I was fiddling with it, I noticed a strange sliding metal piece. It seems to hold a physical switch down on the logic board which seems to tell the dock that the latching mechanism is present (this is the physical switch, not the optical one that signals that the Duo is inserted). Sliding this metal piece doesn't change the fact that it's depressing the physical switch but it does allow the latching clip to stay down. As I took another look at this metal piece, I noticed it extends all the way to the side of the dock to where there's a hole labeled eject. Looks like it's part of the key/lock mechanism and was positioned wrong.

Anyhow, it's sucking in the Duo now which is great.

 

[jmacz]

The metal piece I'm referring to is circled. It moves in the direction of the arrows. It was slid down when I was trying to get my Duo to be sucked and was having issues. Sliding it upwards towards the dock wall resolved the issue. If you look at this metal piece from within the dock bay, you'll see that sliding it down causes the left clip to be moved up and not drop down enough to hook onto the Duo.



Underneath the metal piece you can see the physical switch which needs to stay down in order for the dock to do anything with the motor mechanism. And above the physical switch is the optical switch which is engaged via a piece of plastic on springs that is pushed in when you slide the Duo into the dock bay.

 

[jmacz]

Hmm, this is the icon I see when booting from the Duo Dock. It waits here for 10 seconds before continuing on and booting.



I thought it might be some sensor saying the lid is off? But I don't see any such sensor (and the lid is on). I thought it might have been configured to boot from a duo dock internal scsi drive but Startup Disk shows the right setting (to boot from the Duo's internal drive). Trying search by image on Google but doesn't turn up anything on this particular icon.

 

[Fizzbinn]

Hmm, could that icon be representing the Duo Dock floppy disk drive? I don't recall when machine specific floppy disk drive icons are used but I know they exist and are particularly interesting for Macs that support multiple floppy drives.

Sorry if you already stated, but if you don't have a good PRAM battery/main battery perhaps this the equivalent of the generic floppy question mark icon while the SCSI start disk is found when booting a Duo in a full sized Duo Dock?

 

[jmacz]

Well I guess it is showing off the floppy drive so could be?

My Duo has a brand new PRAM battery inside and it's working. I can pull the battery and all power, come back later and my date/time is preserved.

I did test the floppy drive and it's working great. Reads/writes known working disks.

If that icon is the Duo Dock version of the generic floppy question mark icon, then I'm curious why it's showing that when I do have a scsi device inside and it boots from it 10 seconds later. Mysterious.

 

[jmacz]

Just to test out that idea, I booted with my Duo in the dock, I got that icon shown earlier. I inserted a blank floppy disk. If it's waiting to boot from a disk (ie. it's the generic floppy question mark icon) then it should have started reading the disk. But it didn't. The system was still paused at that weird little icon and then after 10 seconds, it attempted to read the floppy and then ejected it, and then immediately proceeded to boot from the ZuluSCSI I have inside the Duo.

 

[jmacz]

Going to separate out the strange icon into its own thread to see if anyone knows what that is.

In the meantime, I bought a completely trashed second Duo 280c ... screen is either cracked or the top film is in horrible shape from vinegar syndrome (I'm storing this Duo away from any of my other computers to avoid the fumes causing them to suffer from vinegar syndrome). Missing a bunch of plastic parts. There's corrosion on the chassis. Missing the battery, legs, hinge covers. Just in horrible shape. But I bought it cheap for a specific reason. I saw this in the picture.



Pulled it out, cleaned it including the contacts, and popped it into my restored Duo 280c. Yes! Viking 36MB memory module! Which brings me up to 40MB total.

Essentially means everything else was free. I guess I have a backup logic board, backup trackball, and potentially a backup display if it's not cracked and I can replace the outer film.

 

[3lectr1cPPC]

All the updated cap reference info is now up!
Duo 280c: http://www.macdat.net/repair/cap_reference/apple/powerbook/duo280c.html
Duo MiniDock: http://www.macdat.net/repair/cap_reference/apple/powerbook/duo_minidock.html
Duo AC Adapter: http://www.macdat.net/repair/cap_reference/apple/powerbook/duo_ac.html

Thanks for providing the info and photos @jmacz