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

Fizzbinn

Well-known member
*** Originally posted 5/31/2021, reposting due to outage. Thankfully the text was in Bing Cache. ***

The PowerBook AC Adapter (M1893) I got off eBay worked for about 2 days, at least I now know the "sold for parts" PowerBook 540c I got earlier works (and came with a 32MB RAM card!) Getting out the multimeter VMAIN was reading only 2 volts when it should be ~16 volts. VBATT was still 16 volts not that it maters since I don't have any working batteries.


pb500-ac-adapter-pinout.png

So surprise (not), it looks like the AC adapter was in need of recapping. At the same time I really want to figure out (and document) a way to power PowerBook 5xx series without an original AC adapter, which seem to be somewhat less easy to find (and pricier) than other PB AC adapters.
 

Fizzbinn

Well-known member
First up, recapping the original AC adapter. There are a bunch of threads here with advice on this.

<Links lost>

The bottom line seems to be there are no screws in the AC adapter case, opening one up can be quite a challenge, and/or quite easy since the plastics are often so brittle... In my "case" I just gently but firmly squeezed the sides on the seams all the way around and the plastic split along them after a few passes.

Some cracked case pictures:

IMG_1459.jpg

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And the AC adapter internals, note you need to desolder a blob holding a metal shield to a pin on the bottom to be able get to the underside:

IMG_1458.jpg

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PowerBook AC Adapter (M1893) electrolytic capacitors:
(used for PowerBook 520/520c/540/540c/550c)

C1, C2 - 100µf | 200V d:16mm h:26mm
C14A, C14B - 100µf | 25V d:6mm h:11mm
C308A, C308B - 330µf | 25V d:8mm h:20mm
C802 - 47µf | 25V d:5mm h:11mm

Note: C802 is on a daughter board you need to remove to get at. In my case C14A, C14B, C308A, C308B and C802 showed signs of leaking.​

M1893-PB500-AC-adapter-caps.jpg

Next up find replacements on Mouser...
 

Fizzbinn

Well-known member
Switching to the modern replacement, the connector seems to be the biggest challenge. I spent a couple hours looking and couldn't find anything that looked like it would be even close to mechanically compatible. Its like a Mini-DIN connector, but with a custom pinout. To make it even harder the AC adapter cable's connector is female and the Powerbook's is male, the reverse of what you usually see...

IMG_1485.jpg

It seems others have sacrificed their old broken AC Adapters, stealing the cable to graft onto a modern adapter. I guess if my AC Adapter recapping fails I may end up at the same place but I stumbled across a somewhat hacky idea using something that could connect to a single pin. Originally I tried a female Dupont connector breadboard 1-wire jumper but the diameter of the pin on the PB was to large. Further looking I found D-Sub Female Crimp Pins that fit!

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Instead of cutting off the barrel connector from my new AC adapter and soldering these on I decided to create an adapter of sorts.

The 16V 4.5A 72W AC Adapter Charger for IBM ThinkPad I got has a DC CONNECTER SIZE: Internal Diameter: 2.5mm, External Diameter: 5.5mm

So I also got this 5 Male + 5 Female DC Connector Barrel Power Jack, 5.5x2.5mm to use as a breakout (plus spares!). I also decided to use some heat shrink as an insulator for the D-Sub crimp pins.

IMG_1491.jpg

And this is what it looks like all put together:

IMG_1492.jpg

And plugged in, one cable at a time, to the PB VMAIN (black/16v) and GND (white/ground) pins:

IMG_1493.jpg

...but now I'm getting cold feet on actually powering it up (decided to work on this post while I think about it!). I'm wondering if it really is okay not to connect up something VBATT or GND Sense, it seems like leaving out VBATT should be safe, especially considering I have no working batteries that I'd want to charge. GND Sense seems like it could be more important though, I can't seem to find any info specific to the PB 500 series but for other PowerBooks it looks like it might have some specific resistance value to ground? that powerbooks use to determine what type of AC adapter is connected to them.

Anyone know or have thoughts?
 

Fizzbinn

Well-known member
@kalleboo's post (not sure how I missed it in my searches before) has given me some confidence to give it a try!

<link lost>

I especially like the idea of being able to power it via a USB-C battery pack, but it doesn't solve the Powerbook connector issue, @kalleboo used the cable/connector from their dead original AC adapter.

So after seeing @kalleboo didn't connect anything to GND Sense, I decided to reassemble my PowerBook 540c and give the new adapter a try.

...and success!


IMG_1494.jpg

It's certainly not super quick to connect up but it also is not too bad connecting the two wires D-Sub female connector wires. You certainly have to know which pin they need to go to: left side, voltage on top is pretty easy to remember.

I know nothing about 3D printing but I wonder if it would be possible to come up with a barrel shaped D-Sub female pin holder?

So it seems VMain (pin 2) and GND (pin 3) are all that’s needed to power up.

Perhaps GND Sense (pin 4) was optional, something for future use? In newer PowerBooks a sense pin/contact seems to tell the PB how much power it can draw, 45w vs 65w adapters, etc.
 

demik

Well-known member
Good work !

Not sure what the GND Since is for either...
On a side note, PB5xx (without a battery) can work with only 12V. The 540 logic board that I have works just fine with 12V from an ATX Power Supply.
 
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