PowerBook 540c Restoration Project

[3lectr1cPPC]

Yeah I just don't usually bother replacing PRAM batteries unless I have a real good reason. And there really isn't any, unless you have working main batteries. The only one of mine i'm planning on replacing with a new one is my 3400c, and only because I have 5 working battery packs for it so it will charge and you can't swap out battery packs without needing to jump-start off the charger unless the PRAM battery is installed and working. You can warm-boot off a battery just fine without one, but cold booting after it's lost all power requires the charger unless the PRAM battery is installed.

 

[jmacz]

But please please please don't ever replace any backup batteries with alkaline ones, ever! Those things leak basically always after only a couple of years.

Hmm, I have never had an issue with leakage on the coin batteries in any of my decades old machines. I guess I got lucky. Nonetheless, the only coin batteries I use these days are lithium so definitely point taken. Just got used to calling them alkalines so this is my bad.

If you'd like one with the proper cells, there's a guy on eBay building new ones: https://www.ebay.com/itm/325598692922
But it won't ever recharge unless a working main battery is installed, as I believe the PRAM battery is charged off of the main one.

I will put this off until I figure out whether I want to try to put together new main batteries. Thanks.

Yeah I think it's just corrosion. My Dell Latitude CS is built out of a lot of magnesium and is all like that, from both the CMOS battery that leaked and likely also being stored away in a damp basement for years.

Yuck, ok. Thanks.

 

[3lectr1cPPC]

Coin cells may be different, but aren't those almost always lithium? Maybe they weren't 15 years ago. The ones used in laptops were never Alkaline though, always Lithium, NiCad, or NiMH. The latter two of which also have rampant leaking issues mind you, but those only leak after 15-20 years at least.

 

[croissantking]

How possible is it to get a full 040 chip with FPU and replace the LC040 chip?

 

[jmacz]

Coin cells may be different, but aren't those almost always lithium? Maybe they weren't 15 years ago. The ones used in laptops were never Alkaline though, always Lithium, NiCad, or NiMH. The latter two of which also have rampant leaking issues mind you, but those only leak after 15-20 years at least.

These days, yeah. But I would have thought the ones I had in my much older desktops (20-30 years) would have not been lithiums? Maybe I'm wrong.

 

[3lectr1cPPC]

The PowerBook 100 in 1991 used Lithium batteries, and old desktop boards with CR2032s did too.

 

[jmacz]

For the various chassis screws, I believe most of them are 3/32.. but for the pitch, it's definitely finer than 44 tpi but that's as far as my pitch gauge goes so can't tell if it's a 48 or a 56. I think they are #3 3/32-48 but can anyone confirm?

 

[jmacz]

The PowerBook 100 in 1991 used Lithium batteries, and old desktop boards with CR2032s did too.

Ok got it.

 

[jmacz]

For the various chassis screws, I believe most of them are 3/32.. but for the pitch, it's definitely finer than 44 tpi but that's as far as my pitch gauge goes so can't tell if it's a 48 or a 56. I think they are #3 3/32-48 but can anyone confirm?

Or maybe these are #2 56 pitch screws?

 

[MacUp72]

This happened to one of my chassis, after I left it next to a slightly open window during heavy rain and it got wet. I couldn’t clean the white stuff off!

I had this surface corrosion on my 540c, too..in the process of refinishing the machine I also lightly sanded the internal frame, it is made of a very light alloy.



Just a cosmetic thing but I didnt want to this flake off and around the case.
My also have this rare shiny Sharp display, I dont have any probs with it, no bleeding..but sometime I will do a recap.

the loose front flap door, somebody here had a good idea fixing this with a pair of magnets, havent tried that myself but, looks good.

 

[croissantking]

My also have this rare shiny Sharp display,

Is it so rare? I have the Sharp as well.

 

[MacUp72]

..the ones with the matte displays show up more often as far as I have seen.

 

[croissantking]

..the ones with the matte displays show up more often as far as I have seen.

IIRC the other one is made by Toshiba. I wonder if one is better than the other?

 

[3lectr1cPPC]

There was a thread on this a while back. Both are common. The Sharp was more vivid colors but has a higher dot pitch, so it’s up to preference which you prefer.

 

[jmacz]

Or maybe these are #2 56 pitch screws?

I've got a new thread pitch gauge coming... but in parallel I did order a pack of #2 56 pitch (imperial) screws. They aren't metric M3s (they are smaller) and bigger than M2s. Might be M2.5 but I've found most of Apple's stuff is in the imperial / US standard system as opposed to metric. Anyhow, will figure it out.

I was asking because a few screws are missing, and a couple have some rust on them. The internal screws (some of which match the pitch of the chassis screws I am asking about -- and some which are different) are all good. It's the external facing ones that have some rust or are missing.

I had this surface corrosion on my 540c, too..in the process of refinishing the machine I also lightly sanded the internal frame, it is made of a very light alloy.

I am not familiar with this corrosion on magnesium. Looked at a few discussions online on treatment and I don't have the interest (or means) to take approaches like sand blasting it or utilizing strong acids to clean it. What's not clear to me is whether like rust, it will continue to spread even when dry or will stop in its current state. There's some folks who have used WD-40 to help clean it ... not sure how effective that is. I guess I will try and see. With rust I know some folks have painted over it with non-water based paint which seals it and stops it. Regardless if any future damage from this corrosion is slow, then maybe I just won't worry about it as other things will die first before the chassis corrodes away.

Maybe I will try this WD-40 thing and see if it does anything. And then after that, degrease it and just put a coat of paint over it to seal it?

 

[jmacz]

I've got a new thread pitch gauge coming... but in parallel I did order a pack of #2 56 pitch (imperial) screws. They aren't metric M3s (they are smaller) and bigger than M2s. Might be M2.5 but I've found most of Apple's stuff is in the imperial / US standard system as opposed to metric. Anyhow, will figure it out.

Ok. They are NOT #2-56 screws. The thread pitch (56) is right. It looks like they are indeed M2.5 (which also has a 56 TPI). Also the bottom cover has two screws that are smaller. Confirmed those two smaller ones are M2.

 

[croissantking]

There was a thread on this a while back. Both are common. The Sharp was more vivid colors but has a higher dot pitch, so it’s up to preference which you prefer.

Man, I'm just glad it's active matrix rather than passive. I'm super thrilled with my 540c.

 

[3lectr1cPPC]

Or maybe it was a lower dot pitch? I get the two confused. Basically there’s more of that black box around each pixel, if you know what I mean, on the Sharp screen.

And yeah I’m lucky to have one too… mines got the Toshiba screen so no caps to deal with either. That’s definitely a benefit.

 

[jmacz]

There's some folks who have used WD-40 to help clean it ... not sure how effective that is.

I am not sure this is really that effective? I tested a part of the chassis, let it soak in WD-40 for 15 minutes, used a toothbrush to brush the corrosion. Didn't really do much to it to be honest.

I decided to lightly sand it and that cleared it off. I washed off all the dust and degreased it. Then used a heat gun to ensure any remaining moisture was gone. I've given it a coat of corrosion protective/resistive paint. (Will share a picture later). When I go back to putting it together, if I see any places where there is metal to metal contact with this frame, I will sand the paint off in those spots for ground connectivity.

 

[jmacz]

My ZuluSCSI for the 540c arrived. I think this is my 5th ZuluSCSI device. They just work! And their technical support is awesome. Since I live close by, it arrives instantly. Gotta love it. Thanks @rabbitholecomputing!