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550c power issues

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I bought a PowerBook 550c from Japan a year ago that was DOA — wouldn’t start no matter what I tried (no battery of course - was running with an AC adapter only).  After a year in storage, I decided to try to repair it ... plugged it in just for kicks ... and it worked!  The Finder was just loading when I decided to try out the Caps Lock key and ... POOF, it powered down.

 

Since then, I’ve been able to get it to power up only on a few random occasions, and, it seems, for shorter periods each time.

 

I know the power brick is good, it powers up my 540c (which I bought as a parts machine to fix this 550!) and a different 550c with no problem.  AC adapter voltages check out fine.

 

I’ve tried the four-finger salute (Cmd-Ctrl-Opt-Power for ten seconds while unplugged) from this list https://support.apple.com/en-us/HT1781.  Also noted this thread https://68kmla.org/forums/index.php?/topic/56171-powerbook-540c-wont-startup/ but nothing listed seems applicable (for example, the collar piece on my AC adapter plug is nice and tight).  Would love any ideas or advice.  I can take it apart, obviously, but not sure what I’d be looking for once it’s opened up!

 

 

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Well, of course, within 30 minutes of finally giving up and posting to 68kMLA ... I found the problem.

 

My troubled 550c had this Apple PCMCIA Expansion Module installed.  As soon as I removed it ... instant perfect power up and beautiful operation (turns out this guy has 40MB RAM and a 1.6 GB HD with OS 8 installed ... nice).  I confirmed this was the problem by installing it in my other 550c ... it prevents power up on that one, too.

 

Anyone familiar with ease PCMCIA Expansion Modules and what sort of issues they could have?

image.jpg

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Thanks.  Pins all look good.  I did just notice that the left battery compartment where the PCMCIA module had been installed has quite a bit of battery acid residue inside, presumably from a battery that used to live in that slot.  I am now wondering if some may have gotten inside the PCMCIA module and done some damage somehow.

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That sounds like it might be the case, though in any event it sounds like you've got yourself a very nicely spec'd PB550c.  I'm wondering if you also have a CPU upgrade lurking inside.  I thought the max the 5xx PowerBooks could take was 36MB (4MB onboard + 32MB).

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Thanks @EvilCapitalist - and you’re right!  I don’t know much about PowerBooks yet so I didn’t realize the 40MB was a tell, and it’s not listed as “PowerPC Enhanced” in “About This Macintosh” like some I’ve seen (maybe only the Apple upgrades show up like that?) ... but per Clockometer it does indeed have a 117MHz 603e hiding inside.  I hope to take it apart later today.  After using it a bit, it’s amazing how much faster it feels than my other 550c which has a 100 MHz 603e in it.  (Speedometer shows it as almost twice as fast at the CPU test suite?  All that from an extra 117 MHz?)

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Yeah you'd want to investigate the battery acid. Check the solder joints under the power connector and just any other general corrosion on the board, look for green pins on ICs etc. Also I don't know if these have a pmram battery, but if they do that is obviously something that can leak.

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On 12/26/2019 at 11:59 AM, stormy said:

Yeah you'd want to investigate the battery acid. Check the solder joints under the power connector and just any other general corrosion on the board, look for green pins on ICs etc. Also I don't know if these have a pmram battery, but if they do that is obviously something that can leak.

That what I second that too - check for broken/rotted traces etc - my 550c had broken trace which caused issues and since then its fixed.

Cheers

AP

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