PowerBook 540c Restoration Project

[aladds]

• Resistance between pin 14 and 28 - I'm getting 12 ohms.
• Resistance between pin 14 and the ground pad - should be near 0 ohms.
• Resistance between the two ends of the capacitor circled in yellow - I'm getting 12 ohms between them and it's buzzing when in continuity mode.
• Resistance between pin 28 and the top side of the capacitor - should be near 0 ohms as they are connected.
• Resistance between pin 14 and the bottom side of the capacitor - should be near 0 ohms as they are connected.

14-18: infinite
14-ground: 1 ohm
measurements to capacitor: I don't have that capacitor on my board...

 

[jmacz]

@aladds did you mean 14-28? Just want to make sure it was pin 28, not 18. Your board is slightly different, not just with that capacitor that isn't there but also the diodes at the far end are arranged differently. But nonetheless, looking forward to confirmation on pin 28 vs 18.

If it's 28, then it does sound like I have a partial short inside the IC as I suspected.

 

[aladds]

Yes 28 - corner to corner. Apologies for the confusion!

 

[jmacz]

Yes 28 - corner to corner. Apologies for the confusion!

No problem! Thanks for the confirmation.

 

[3lectr1cPPC]

Still need me to measure out anything? Sorry for taking so long, got sidetracked and forgot.

 

[jmacz]

No need, I am good. Thanks!

 

[jmacz]

I procured another battery. I had to pick up a cheap and dead 520 to get the battery. Craziness.

I took this one apart and as usual the cells were leaking everywhere. Part of the ribbons were eaten through. This board also had a different layout.. different than mine, different than @aladds, different than a picture I saw of @3lectr1cPPC's battery. The Apple chip tested ok, unlike mine this one had infinite resistance across pin 14 and 28.

I took the cells out, cleaned up the insides, put new wires in instead of the half eaten ribbon, and placed my NiMH AA's inside. Battery was detected by my 540c but both Lind and EMMpathy were complaining about corrupted memory. Tried numerous times with both utilities but same error.

I had an extra memory chip from when I replaced the memory on my other battery so I replaced the memory chip on this one as well. Popped it in and Lind was able to write over the whole thing and get it right. EMMpathy was happy with it also after Lind had rewritten the memory. So all good there.

As of right now, the new battery seems to be working. My 540c can boot and run on the battery and it seems to be holding.

I did find one issue though. My stock power brick seems to be going bad. The Vmain side seems ok but the Vbatt side seems to be failing as during charging, it keeps stopping for a bit every minute or so.

Anyhow, back to this dead 520 I got. The power adapter that came with it is dead. I cracked it open and I don't see any obvious leaking from the caps but the fuse is dead. Need to figure out what the rating on it is and try replacing it first. But the case broke apart into lots of pieces, the plastic was really brittle. In fact, I used my hand to open it as only a little pressure actually caused the seam to crack.

As for the 520, screen is trashed. It's bubble, has dark marks, and looks like the top layer is peeling off. Not sure what happened to this thing. The 520 also won't start, no power. I took the thing apart and found the power socket was loose. Resoldered that and the 520 powered up. Hard disk, floppy drive, keyboard, touchpad, all seem to work. But the screen is dead. The backlight works but nothing is displayed. Figures, since the outside like I said was completely trashed. I had to use the display off my 540c to test this thing.

At least I got a working battery. And I've got a bunch of extra parts now.

 

[3lectr1cPPC]

The 520 screen sounds like it has Vinegar Syndrome: https://macdat.net/important_issues/vinegar_syndrome.html

 

[jmacz]

Oh, and unfortunately, that custom power supply I built, I had to crack it open and take it apart. I didn't want to leave it as is and risk the potential of someone (myself) plugging it in and sending 4A to the battery. So took it apart and will revisit it later once I figure out how to ensure the Vbatt side is current limited to 2A.

 

[jmacz]

The 520 screen sounds like it has Vinegar Syndrome: https://macdat.net/important_issues/vinegar_syndrome.html

Ah, that sounds like exactly the problem I have. I guess I have another project at some point, to fix this screen.

 

[jmacz]

Also, I've got some weird issue where after going to sleep, the system won't come back, this is even without any battery and just the power supply connected. After wake up from sleep, the display comes on, but everything just freezes. Happens even with extensions disabled.

This issue is not happening anymore so it's not due to the lack of a spinning disk (I have a ZuluSCSI in there). I think it was due to the PRAM battery.

I noticed that after I had gotten the battery working yesterday, that after I unplugged the machine from the charger and removed the battery, trying to boot the machine off the battery later didn't work. It wouldn't detect the battery again. But plugging in the charger and then putting the battery, it started working again. I then remembered the exchange in this thread between @3lectr1cPPC and @alexGS, and indeed, looks like if the PRAM battery is dead, the main battery won't detect after removing it/re-inserting it without the charger plugged in.

So I left the battery in the laptop (without the wall charger) and left it for hours to charge the PRAM battery (which is a new battery I built using new panasonic coin cells). And after a few hours, everything's working. I can leave the battery out, no wall charger, the date/time keeps, and the battery can be reinserted and boots the machine. Good news all around.

Now to continue searching for one more battery... either to have two batteries inside this 540c or I can use it on this 520 if I ever get the screen repaired. Or if I can find a donor Apple chip from a dead EMMboard, that'll work too.

 

[alexGS]

So I left the battery in the laptop (without the wall charger) and left it for hours to charge the PRAM battery (which is a new battery I built using new panasonic coin cells). And after a few hours, everything's working. I can leave the battery out, no wall charger, the date/time keeps, and the battery can be reinserted and boots the machine.

Nice, yes, I found the same, except only one of my original PRAM batteries charged in this way, the other two seem not to charge enough, even though I tried charging one on a bench power supply for a few hours. I guess I’ll have to order new VL-2330s after all.

Interesting that you had a main battery that worked for a while (after you re-celled it) and then stopped being detected, I had the same happen. But my second re-celled battery is working well.

And yes, my 520 has dark marks, and a brown blotch in the centre - the start of vinegar syndrome on the rear film, I think. Even my 520c displays have uneven colour, which is especially noticeable on the nice terracotta desktop patterns.

One day perhaps I’ll replace the polarising film, I will try a new source I have (thanks to a Google search result that turned up a Reddit thread) - someone with a 540c had used this with success:
NZ$59.77 4％ Off | Free Shipping!!!New 12.1" 4:3 45 degree Dark Matte LCD Polarizer Film for tft Screen

https://a.aliexpress.com/_mOt4J6M

 

[jmacz]

Interesting that you had a main battery that worked for a while (after you re-celled it) and then stopped being detected, I had the same happen. But my second re-celled battery is working well.

Yeah. Well this current pack is the same cell pack, but different emm board due to the issue I had with the internally shorted apple emm chip. Both boards have new memory chips though. And this second board is working fine now.

Trying to learn what I need to know to attempt a current controlled/regulated circuit for the power supply replacement. Trying to see if it’s doable with an LM317.

And yes, my 520 has dark marks - the start of vinegar syndrome. One day perhaps I’ll replace the polarising film, I will try a new source I have (thanks to a Google search result that turned up a Reddit thread) - someone with a 540c had used this with success:
NZ$59.77 4％ Off | Free Shipping!!!New 12.1" 4:3 45 degree Dark Matte LCD Polarizer Film for tft Screen
https://a.aliexpress.com/_mOt4J6M

I will also have to try this at some point.

 

[3lectr1cPPC]

The 540c is a TFT color screen and the 520 is a STN/DSTN grayscale screen. They'll likely not use the same film if I had to guess, not sure though.

 

[alexGS]

The 540c is a TFT color screen and the 520 is a STN/DSTN grayscale screen. They'll likely not use the same film if I had to guess, not sure though.

Yes, the greyscale display should have a different film with retarder layer; but this really doesn’t seem to be available. If anyone finds a source, please let me know. With the standard film, the result will probably be a bluescale or purplescale display with yellow-ish background. I’ve ordered the film I linked to above and will try it out on my 520 display (and my 520c).

 

[jmacz]

And after a few hours, everything's working. I can leave the battery out, no wall charger, the date/time keeps, and the battery can be reinserted and boots the machine. Good news all around.

Still looking good after a day. 540c has been off the wall charger since yesterday and I have been booting it up from time to time, also with periods of leaving the battery out of the machine. Date/time is holding and laptop continues to be able to boot if I put the battery back in, without having to plug it in. So sounds like this battery is back. (knock on wood).

 

[jmacz]

Battery has gone through its first week and seems to be holding charge well, lasting a good amount of time, and overall, the 540c feels like it's fully restored and working properly. I'm pretty happy about this. I had one of these almost 28 years or so ago, and to have it back and working like it did back then is really cool.

Still hunting for some more batteries as I'd love to have both battery bays going at the same time.

 

[jmacz]

Made some revisions to the front bezel model for better fitment. Attached the STL models to this post.

 

[3lectr1cPPC]

I'll update the models on my website with these new ones next update.

 

[jmacz]

Another option. For folks that have a front bezel that is intact except for the clips that have broken off, here are a set of clips you can glue onto the stubs to fix them.