PowerBook power adapter compatibility?

[JDW]

I'm sure the exact technical reasoning is buried in a tech note somewhere.

The rabbit hole opens and now the heat is on the find that elusive tech note!

 

[Fizzbinn]

Great archive resource on old Apple tech notes here:

https://savagetaylor.com/til/articles.html

TIL16168 - PowerBook: Battery, Recharger & AC Adapter Identification
Slightly different versions:

https://savagetaylor.com/TIL/TA32393.html

AppleCare Tech Info Library -PowerBook and iBook: AC Adapter, Battery, and Recharger Identification

https://www.savagetaylor.com/TIL/TIL16168.pdf

 

[JDW]

@Fizzbinn
Thank you for the links. No scary warning that I could find (yet) about AC Adapters rated for more Amps than the stock Adapters, but the search is still on for that.

I see in some of the documents you linked that NiCd batteries were mentioned. I've seen people replacing those with NiMH cells even though the PowerBook's charging circuit was designed specifically for NiCd. I guess this is yet another case of people not really knowing what's best simply because many people have tried it (NiMH) replacements and they seem to work. Arguably, they are a vastly better choice than NiCd, but the concerns about the charging circuit remain. You don't want to overheat or overcharge your batteries.

 

[Fizzbinn]

@Fizzbinn
Thank you for the links. No scary warning that I could find (yet) about AC Adapters rated for more Amps than the stock Adapters, but the search is still on for that.

The only scary note like that I see is for the APS-17adp AC Adapter:

The fourth AC adapter, 17 W, shipped with the PowerBook 150, and works with the PowerBook 100 or 150.
Note: AC adapters producing more than 19 watts can damage the PowerBook 100 and 150.

 

[joevt]

Actually, you need to go back to the Macintosh Portable to understand. It's not Ohm's Law. The Mac Portable's power system was really a crazy design because if you used another AC Adapter with the same voltage but higher current (even only 1A higher current output), that would fry motherboard components over time!

Because the PB100 design is basically just a Mac Portable in a smaller case, some fear the same bad power design could be used and therefore are wary about using a non-stock AC Adapter (or one that has higher current). It seems that other PowerBooks might be okay, but @Daniel Hansen posted earlier than the PB150 is probably not OK and is like the PB100.

I myself don't really know what will happen if you match a 5A AC Adapter with a PowerBook 165c or 180c, for example. I think we are all afraid to try. But what we do know is that if you use an adapter with too low a current rating (2A rather than 3A for a 180c, for example), the machine won't power on.

You're saying that Apple put current limiting features in the power adapter instead of inside the Mac. You can't use third party power adapters if that's true. You would have to test the adapter to verify how much current you can draw from it. What happens to the adapter when that current limit is exceeded? A fuse would make it inoperable until it is replaced.

Note: AC adapters producing more than 19 watts can damage the PowerBook 100 and 150.

This note is almost useless. Watts = Volts x Amps. Which quantity causes the damage? Can you use an adapter that's 19V 1A? 1V 19A?

Adapters have Volts. There's no current or power until something is connected to it. If you connect a wire (small resistance) between + and -, then you have a short and you get lots of current/power until something melts. Apple adapters have something other than a fuse that makes a short not happen?

 

[Windoze]

@joevt Current limited power supplys usually reduce the voltage to maintain the maximum current.

 

[JDW]

You're saying that Apple put current limiting features in the power adapter instead of inside the Mac. You can't use third party power adapters if that's true.

Actually, you can. I know people who have safely used modern AC Adapters with their Portable but those Adapters match the Apple Adapter in terms of output being 7.5V @1.5A. Voltage and Current output must be the same, and such Adapters do exist. Tolerances of those modern Adapters (as reported to me by others — I've not tried them) seem to be tight enough on the modern adapters such that very slight variation of voltage and current doesn't cause damage. Of course, the issue comes down to how slight, but I guess 100mV and maybe 200mA.

My Macintosh Portable uses a Battery Eliminator which means I can use any AC Adapter I like (even a 5A adapter), so long as the voltage is right. That's because the Battery Eliminator is an add-on card that charges up super capacitors and eliminates the need for a battery. It bypasses the plug you normally use for the AC Adapter entirely. Instead, you plug your Adapter into the Battery Eliminator card. I think it's great because batteries are a pain, and the other benefit is you don't need to worry about having an Adapter that outputs "too much current."

What happens to the adapter when that current limit is exceeded? A fuse would make it inoperable until it is replaced.

The motherboard burns and heatsinks change color, as @techknight clearly shows in this video (an absolute MUST WATCH):

This note is almost useless. Watts = Volts x Amps. Which quantity causes the damage? Can you use an adapter that's 19V 1A? 1V 19A?

I cannot give you an exact answer because I do not know, but I can tell you that both VOLTAGE and CURRENT are likely going to be an issue if either way off the nominal values, just as they are on the Mac Portable. Put 7.5V @ 2.0A into a PowerBook 100 and it works great. Use the same Adapter on a Portable, and you'll see what you saw in TechKnight's video above. (Also see my spreadsheet for specs.) But put 9v @2.0A into a PB100? You're likely going to fry something. Put 7.5V @ 3.0A into a PB100? I'm guessing (haven't tested, so I don't know), that the same thing that happens to a Mac Portable will happen to the PB100; namely, that something will overheat or fry. The Apple Tech Note seems to indicate that to be true.

In other words, your output voltage and output current will clearly have certain allowable tolerances for the machine to run without issue. Exceed the tolerances, and sadly things will fry.

What are the tolerances? I do not know. And like you, I don't like "not knowing." But for now, we simply do not know.