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PowerBook 5,7 (17" 1.67) only works on battery

munchausen

macrumors newbie
Original poster
Oct 22, 2020
6
2
Hello! I am a regular reader of this sub-forum, owning several powerpc macs mostly as a curiosity, except my emac which lives on my desk and most of the time runs debian sid. I've never had cause to join the forum until now...

I've always wanted a 17" powerbook and picked up this one for not much as it was spares/repairs. It has taken an impact on the back left corner and although it will charge the battery and runs fine from the battery (for about 40 minutes), if the mains power (65W) is connected it will not power on (the screen comes on but stays black). If the power is connected while it is turned on it immediately gets crazy graphical corruption that changes for a couple of seconds and then it freezes. Booting it again requires removing the battery and power cable. I've got it apart and inspected it and can't see anything obvious (I'm an embedded engineer as it happens).

The DC power board is obviously suspect, as it is in the area of damage, but aside from possibly shorting out it looks very simple and I'm thus not convinced that it isn't working. Before randomly replacing parts I was wondering if anyone knows where I might find the schematics (for any of the powerbook G4 17" machines, I presume they all have almost identical DC boards) so that I can check what voltages I should be expecting on the output. Or if anyone has any further suggestions?

I have tried all the usual suspects in terms of resetting nvram etc already.

My other thought is perhaps a voltage regulator on the motherboard. I have already checked all the fuses on the motherboard and DC board and they are all fine. I guess I should try to identify that SOIC-8 on the back of the DC board.

Thanks very much :)

EDIT: I found the schematics for this machine and have attached them here, is that OK? I haven't had a chance to look over them properly yet.
 

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  • 820-1688 051-6694 MLB PB17'' Rev G Schematic Diagram.pdf
    1.2 MB · Views: 28
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munchausen

macrumors newbie
Original poster
Oct 22, 2020
6
2
I just tried it with a 45W adaptor and it seems quite happy. It lasted a few minutes and then crashed horribly.

It looks as though the type of charger is detected by the logic board (rather than DC board) so I guess something is up with part of the power circuit. I am not sure what the limitations of using a 45W adaptor are (will it charge the battery)? I will stick with the 65W for now.

I also wonder if this is just a case of a faulty battery. After crashing it went from reporting as fully charged (all lights lit) to empty.
 
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weckart

macrumors 603
Nov 7, 2004
5,180
2,567
I just tried it with a 45W adaptor and it seems quite happy. It lasted a few minutes and then crashed horribly.

It looks as though the type of charger is detected by the logic board (rather than DC board) so I guess something is up with part of the power circuit. I am not sure what the limitations of using a 45W adaptor are (will it charger the battery)?


The 17" 1.67GHz came with a 65W adapter. That might be the reason.
 

munchausen

macrumors newbie
Original poster
Oct 22, 2020
6
2
Last edited:

munchausen

macrumors newbie
Original poster
Oct 22, 2020
6
2
After some digging I have also found the schematic of the DC in board
 

Attachments

  • 820-1617 051-6600 DINO Q41A Rev 01 Schematic Diagram.pdf
    132.3 KB · Views: 8
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B S Magnet

macrumors 6502a
Dec 5, 2018
632
715
no don’t read my status message
After some digging I have also found the schematic of the DC in board

Sidebar: I’m kind of impressed you’re able to find these. In past attempts to find board schematics and diagrams for other Macs, the best I’ve ever mustered is finding the occasional dubious site claiming to have this stuff but for a special time-based access price.
 
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munchausen

macrumors newbie
Original poster
Oct 22, 2020
6
2
Sidebar: I’m kind of impressed you’re able to find these. In past attempts to find board schematics and diagrams for other Macs, the best I’ve ever mustered is finding the occasional dubious site claiming to have this stuff but for a special time-based access price.

My google-fu is strong! I guess I've spent a lot of time looking for technical documents, maybe there is a knack to it. I hit a lot of dead ends before I find what I'm looking for...

I've checked half the DC in board and it looks OK. What is odd is that, if I am understanding correctly, the 65W adaptor is detected as 45W. There is a line between the DC board and the logic board called ADAPTER_DET, whose voltage determines which PSU is connected according to a table on page 31 of the logic board schematics. On this machine, when the 65W PSU is connected (machine off), the ADAPTER_DET pin has 2.66V to ground. This makes it identify as a 45W adaptor. With a 45W adaptor connected the ADAPTER_DET pin has 3.3V, which makes it a "hooper", whatever that is. With any luck I've just got to keep following the bread crumbs...

The above was a misnomer...I'm fairly sure the table actually refers to the AC DET signal, which is derived from ADAPTER_DET. The threshold voltage for deciding between 45W and 65W is 2.31V which lines up with the 2.34V that the comparator U27 compares to AC DET. AC DET with the 65W adaptor is 2.1V, with 45W it's 2.6V, so this fits. No problem there then.
 
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CooperBox

macrumors 65816
Nov 28, 2010
1,356
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France - between Ricard & Absinthe
Excellent work in finding those schematics, which I'm sure could be useful to many. Not so much for myself I hasten to add, as even attempting to read a Metro/subway network brings on a migrain......😜 I wish I had even a quarter of your knowledge 'wiggly-amp' wise.
A long shot, but is it possible that your's came with a cheap & not-very-cheerful 'knockoff' non-Apple 65W charger? If you could beg or borrow a genuine Apple 65W charger, that would at least illiminate the possibility of yours being defective in some way.
 
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munchausen

macrumors newbie
Original poster
Oct 22, 2020
6
2
A long shot, but is it possible that your's came with a cheap & not-very-cheerful 'knockoff' non-Apple 65W charger? If you could beg or borrow a genuine Apple 65W charger, that would at least illiminate the possibility of yours being defective in some way.

I had the same thought, but actually it came with a 45W charger (which I think is nonetheless genuine). I asked the seller if they sent the wrong charger but he said it was the only one. However I already have an ibook G4 and a powerbook G4 15" so I had both 45W and 65W PSUs already and can confirm they work on other machines.

I think it's going to be rather arduous finding the issue but I should get there in the end. It looks as though nothing really bad is wrong with the machine because it works 100% when on battery. So there's a very good chance the problem is in the power section of the machine, and although it's a bit of a mammoth power section all the parts are reasonably straightforward to replace if I can just find which one is unhappy (no BGAs). Fingers crossed anyway!

I have ordered another bottom case and the trackpad/keyboard surround case part, since currently one of the back corners of the machine is bent upward at a worrying angle and the laptop doesn't really close properly, and is also missing some of the plastic trim around the optical drive. I think I also need new pram cells and a main battery. I had to stop myself buying a high res LCD yesterday! I guess that can be a reward if I get it fully working again!
 
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