PB 5xx original AC adapter re-cap & modern replacement

[3lectr1cPPC]

My second supply typically stays on for longer and when it does, there’s no ticking noise and both voltage rails are just dead if I’m remembering right. Also no battery warning. That makes me worry some major component is failing other than a capacitor since both rails just die…

 

[jimjimx]

I ended up replacing my PB520 PSU with one from a IBM laptop, and spliced the old 520 cable onto it... I kept the original PSU, but there's to much magic smoke inside for me to bother with... It's far smarter for me, to use a modern power supply..
New one is IBM 16v 4.5A

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[jimjimx]

Here’s a picture of the bottom of my board
View attachment 58450

A whole lot of those old solder joints look cold and dry... They absolutely need flux and heat!

 

[3lectr1cPPC]

I went before and reflowed anything that looked even slightly suspicious (or large) and yeah no change. I didn't use any flux though, I guess I could go back and do that but at this point I can't see it doing much.

I did manage to get a solid hour out of the second supply today though, which was a surprise. It died after and hasn't been well for the rest of the day though, it wouldn't run at all even multiple hours after it died after that hour and when it finally did start it only ran for a couple minutes. Also noticed one of those times that it appears to be a voltage dropoff, not a sudden death. I measured 100MV out of VMAIN quickly falling, I assume it just dropped from spec and by the time I got a probe on it it was that low.

 

[MacUp72]

that dying is strange, maybe there is something wrong with the powerbook's power board ?

 

[croissantking]

Any PSU experts in the house?

 

[3lectr1cPPC]

that dying is strange, maybe there is something wrong with the powerbook's power board ?

I’ve got two separate PowerBooks, my 540 and 540c and both do the same. Plus these don’t have a normal DC section with a bunch of big electrolytic caps like later models and the Duos do, its DC/DC section is solid state. It’s got one electrolytic that I do need to change out eventually near the battery bays, but that’s for battery charge alone.

I think I’ll just build a modern one. I’ve actually got that exact IBM charger linked above but I’m not going to sacrifice that one as I do use it with my ThinkPads. I’ll probably get another one.

 

[croissantking]

I think you’d be wise to cut your losses, this PSU is a piece of junk!

Just note that you won’t be able to charge any batteries with a new build PSU, unfortunately…

 

[3lectr1cPPC]

I could probably buy two modern small form factor 16v PSUs and then wire up both lines if I needed to. Not that I have any working batteries at the moment.

 

[MacUp72]

And of course before using them it is necessary to assemble them completely, which means soldering back the top metal shield with that little wire through it.. but I guess you already did

 

[3lectr1cPPC]

I’ve been doing that, yes.

 

[mustagcoupe]

The adapter for my 520c was becoming unreliable and would sometimes fail to power up the laptop. I cut the cord off and soldered it to a barrel jack salvaged from a dead pc laptop and sealed it with heat shrink tubing. This way I can use any standard unmodified PC laptop power brick supplying 16v and also one less power brick I have to keep around.

I wired both vbatt and vmain to the positive pin on the barrel jack. On my cord both gnd and gnd sense were connected to pin 3 and pin 4 was unused, both are connected to negative on the barrel jack. Not sure why apple wired the battery and main supplies separately since they are both the same voltage. I don't have a battery to test if it still charges this way but the 520c itself is working normally

 

[3lectr1cPPC]

That’s similar to something else I want to do - I want to see if I can find a small-ish power supply that had a widely variable voltage and amperage control, like a bench top PSU but not as powerful and more portable. Would ideally be able to go from 5 to around 25-30 volts and then create my own custom modules for it with all the weird connectors laptops used. That way I could build my own custom universal supply that’s better than off the shelf ones because I could design my own adapters for it. Just something I want to do someday.

 

[Forrest]

A universal power supply sounds like a bad idea. I can imagine the voltage switch getting bumped accidentally, instantly frying your PowerBooks internal power supply. As an alternative, there is an Amazon link on page 1 of this thread for a 16V DC power supply that is still available inexpensively.

 

[3lectr1cPPC]

Obviously I’d design it in a way that that would not be easy to happen, but I see your point. Would have to be careful for sure.

 

[MacUp72]

for my 520 I used a universal Hama power adapter with switchable voltage and soldered the plug to it, worked without any problem.
The voltage changing switch is recessed and actually a bit hard to change against unintentional switching.
With that setup you cant charge the batteries of course ( ony 1x 16V, not two).

 

[mustagcoupe]

That’s similar to something else I want to do - I want to see if I can find a small-ish power supply that had a widely variable voltage and amperage control, like a bench top PSU but not as powerful and more portable. Would ideally be able to go from 5 to around 25-30 volts and then create my own custom modules for it with all the weird connectors laptops used. That way I could build my own custom universal supply that’s better than off the shelf ones because I could design my own adapters for it. Just something I want to do someday.

The variable voltage power supply seems unnecessary. Pretty much all laptops use either 16v or 18.5v, most of them with a 5.5 x 2.5mm barrel jack. So if you build a cable or adapter from 5.5mm barrel jack to each non standard jack you'll probably only need 2 power bricks. My preference is the massive 6-7 amp power bricks that came with some large desktop replacement or gaming laptops. Running a normal laptop that uses 1-3 amps they barely heat up which should increase their longevity and stability.

The issue with a variable power supply is if you accidentally leave the switch on the wrong voltage. If you accidentally plug an 18.5v power brick into a 16v laptop it shouldn't really hurt anything, they just get hotter than normal from the vrm working harder. But if you accidentally send 30v into a 16v laptop it will probably hurt something. If you have equipment that uses 24v or 30v or whatever I would use a separate brick with a different size plug so it's impossible to mix up the 30v adapter with the 16v and 18.5v ones.

 

[3lectr1cPPC]

A couple of 16 and 18v supplies wouldn’t fit my needs, I’ve got a bunch that take 20 and over. The PowerBook Duos, 5300, 1400, 2400, 3400, G3 iBooks all take 24v. And then the 100 series PowerBooks only take 7.5 IIRC. My Dell laptops with the weird 3 prong connector need 20V. So it would really need to be variable to fit my needs.
If I were to make such a thing I’d make in a way that accidentally hitting the switch or dial would be difficult, and it would in the end be up to me not to screw up and power a laptop with the wrong voltage. I’d be very careful in that instance.

Currently I do have most of the weird supplies that I do need. I’ve got two of the weird dell ones, four of the large audio jack style apple ones, and so on, but they’re all pretty old and I don’t like relying on old PSUs if there is an alternative. Just food for thought at the moment though.

 

[mustagcoupe]

A couple of 16 and 18v supplies wouldn’t fit my needs, I’ve got a bunch that take 20 and over. The PowerBook Duos, 5300, 1400, 2400, 3400, G3 iBooks all take 24v. And then the 100 series PowerBooks only take 7.5 IIRC. My Dell laptops with the weird 3 prong connector need 20V.

I hadn't noticed that the mac laptops with the headphone style power jack were 24v, I assumed they were 18v like the magsafe laptops. Never noticed the 3 pin dells being 20v either. My adapters for them are in good shape so I never looked that closely at them. I guess I've been lucky that almost every laptop I have is 16 or 19v and anything that isn't still has a good condition power supply.

For your variable power supply you could use a 24v power supply and fixed voltage step down regulators for each voltage as necessary. It might be cheaper and easier than a fully variable power supply. You could integrate the voltage regulator into a module for each laptop or put them all in some kind of box with a jack for each voltage on the front.

 

[3lectr1cPPC]

I had thought about that actually earlier today. Would be neat if I could integrate an automatic voltage switch or something inside of each tip instead of relying on a dial that I'd have to set each time, would kill two birds with one strong. So yeah that may be the way to go. I'd just have to find a high quality self-contained step down converter for each voltage, seems doable.

What's really annoying about the 3-pin Dells is that halfway through their use of them they switched the key of the tip and the voltage. The XPi and LM series used a 16v with the different keying IIRC, and starting with the CP/C series and associated Inspirons is when they switched to 19/20V and the more common keying. I've seen plenty of cheap untested Latitude XPis and LMs on eBay that I'd loved to have bought to mess with but I've yet to find one of the earlier chargers. You can pretty easily modify a later C-series charger to fit in the earlier ones, but the voltage is trickier.