Macintosh Portable & Powerbook 100 power adapter bench

[moldy]

Online, you can find a lot of discussions related to what power brick to use with Macintosh Portable (the original is M5136 7.5V 1.5A), if it has to be exactly 1.5A or can be more and if it’s worth recapping the power supplies.

I decided to at least somehow help in those discussions with verifying two hypotheses on the bench:

• Is it worth recapping?
• What is the voltage-current curve of the Portable power supply and to what extent does it differ from an Apple 2A power supply. This would permit others to potentially measure and select the power supply with the closest characteristics.

So I took 3 PSUs on my bench:

• M5136 7.5V 1.5A (Macintosh Portable)
• M5651 7.5V 2A (I usually saw it with PowerBook 100, it’s 15W nominal, but the Apple Technical Article claims it’s 19W?)
• ADP-17AB 7.5V 2A (PowerBook 150)

By the way, here’s the archived Apple Technical Article about the PSU part numbers:
http://web.archive.org/web/20100423034550/http://support.apple.com/kb/TA32393

Is it worth recapping?​

Yes, definitely!
The old capacitors in those PSUs tend to lose rated capacitance and leak. The current curves in my case were slightly affected by the capacitors, I’m pretty sure that dynamic characteristics (eg. impulse response) would make it even more apparent.

Leakage is another problem - the capacitor goo really eats out the soldermask and copper traces, making the PSUs simply non functional. Out of the three, ADP-17AB had pretty apparent traces of capacitor leakage:

The voltage-current curves or what is the difference between the adapters?​

I decided to spin an experiment and load the PSUs with various combinations of power resistor to record their voltage-current traces.

Here’s the result:


Conclusions?

• The output voltage of M5136 (Mac Portable) strongly drops at 1.5A, but even at 1.0A it’s only ~7.25V. It’s also clearly visible how the recap helped, before at 1.0A it was even lower at 7.0V!
• M5651 and ADP-17AB behave pretty much the same and could be considered interchangeable.
• Recapping of ADP-17AB made a big difference under load starting at 1.0A. At 1.5A, it brought about 400mV difference and 2.0A even slightly more.

 

[3lectr1cPPC]

Ooh we got carts! Very nice and great info.
Question though: I’m assuming your 150 adapter was a “low power” labeled one, right? If so, did it have the ELNA caps inside? And did the portable adapter have those in it too?

 

[moldy]

Question though: I’m assuming your 150 adapter was a “low power” labeled one, right?

Yes, exactly, it is marked as "low power". In my case (but obviously it depends on the history of use and the storage conditions), it was the one in the worst condition of all three.

Ooh we got carts! Very nice and great info.
Question though: I’m assuming your 150 adapter was a “low power” labeled one, right? If so, did it have the ELNA caps inside? And did the portable adapter have those in it too?

I did this recap a while ago and honestly I didn't take detailed pictures of the caps. I have a few overall pictures where you can see/guess the following:


And the Portable one:


It looks like those had fewer Elnas compared to M5140X described here: https://goughlui.com/2016/09/19/repair-apple-macintosh-powerbook-100-ac-adapter-m5140x/

 

[3lectr1cPPC]

Alright well that’s good at least. Sure, all caps fail eventually, but not being an ELNA does sure increase the chances of them being ok.
Now I only wonder whether my 3A color unit charger has them. Mine still works so I haven’t opened it yet.

 

[Phipli]

Alright well that’s good at least. Sure, all caps fail eventually, but not being an ELNA does sure increase the chances of them being ok.
Now I only wonder whether my 3A color unit charger has them. Mine still works so I haven’t opened it yet.

The "Long Life" ELNA caps in my LC PSUs had all catastrophically failed. The other caps were all fine.

 

[3lectr1cPPC]

The fact that they say “Long Life” on them just makes it funnier that they’re the worst when it comes to leaks. Sure, 30 years could be classified as a long life, but it’s not a good look when the nearby Rubycons are all fine…

Beyond the LC, IIsi, PowerBook power supplies, they also ended up in the DC/DC sections of a lot of Toshiba laptops from that general time, and as such many are being rendered destroyed by catastrophic corrosion from them. Real shame.

 

[robin-fo]

The "Long Life" ELNA caps in my LC PSUs had all catastrophically failed. The other caps were all fine.

Same in the IIsi PSU

 

[stepleton]

The "Long Life" ELNA caps in my LC PSUs had all catastrophically failed. The other caps were all fine.

Can also report disaster ELNA "Long Life" caps in a NeXT monochrome display. A real mess.

 

[cheesestraws]

It's nice to see some empirical measurement of this kind of thing. Nice graph!

 

[mg.man]

Same in the IIsi PSU

Totally... I've had at least four lately where the LL ELNAs had spilled their guts.

 

[CC_333]

I should probably recap my Portable's AC adapter at some point. I think the battery has some life in it, since it does at least power on, but it's too weak to run the hard drive or floppy.

I have a battery maintainer meant for automotive batteries that I think can work on 6 volts (which the Portable's battery nominally is). I wonder if that would help?

c

 

[Juror22]

I have a battery maintainer meant for automotive batteries that I think can work on 6 volts (which the Portable's battery nominally is). I wonder if that would help?

I've used one of those to 'keep up' the rebuilt 6 volt batteries for my Portables when the computers are in storage - they seem to do fine, otherwise, they would be dead in under a year. Mine has two settings, a 'quick charge' (which I do not suggest) and a very slow charge that I use for this work.

 

[CC_333]

OK. I think mine's dead, unfortunately, but maybe I can eke a bit of life out of it if I put it on the maintainer?

I don't use my Portable much, so getting a new battery at this point would probably be a waste, as the same thing would likely happen again.

c

 

[Joopmac]

Hello all
Can anyone hint how to build this test rig setup for testing voltage under load?

 

[moldy]

Can anyone hint how to build this test rig setup for testing voltage under load?

Hi, it's relatively simple:
- You need a load, in this case power resistors. I had a box with a few of them and tried different combinations to get curve points for different loads (the lower the resistance, the more current will flow).
- You want an ammeter in series with the load to measure the current.
- You want a voltmeter in parallel with the load to measure the voltage on the load.

By changing the resistance of the load (the resistor combination), you will be able to record the points on the curves in my plot above. You can connect the resistors in series and in parallel to get different resistances.

Note that the power supplies are 15W max which means there'll be quite some heat and you probably want 20+W resistors (or a series combination of resistors that can handle this power).

 

[Joopmac]

Awesome!! Lets try it
Is it common to have to adjust the voltage after recapping?

 

[desertrout]

Awesome!! Lets try it
Is it common to have to adjust the voltage after recapping?

In my experience... yes, sometimes. Thankfully there's a pot for it. I aim between 7.6 and 7.8 (Service Guide says 7.5 - 7.9)

 

[jjclay]

Hi guys. During recapping of my PowerBook AC Adaptor (M5140B, a 2A model) I noticed a rather unhealthy looking diode, D104 (see pic - it's located between D105 and C111 on the main board). Can anyone tell me what diode type & rating this is please? All I can see is the crack! Thanks, JD

oops! I think I answered my own question? it's a teeny healthy diode with a ferrite bead, not a broken diode! learn something every day...