A faulty Powerbook G4 12" Aluminum

[quantumii]

Hi,

I just got myself a decent Powerbook 12" (The 867Mhz variant), and so far I have only managed to get it to boot twice, with several (in the tens) attempts in between.

When powering on the system, one of the 4 scenarios below occur:

- Power on and boots fine (Only happened 2 times out of 50+)

- It powers on , the HDD spins and the DVD drive initializes. It will also chime. Then nothing...

- It powers on, the HDD spins and the DVD drive makes a noise only. Noting more.

- It powers on, the HDD spins. Nothing more <- This one is the most common.

I did a complete teardown and reassembly, and the problem is just the same. Basically dead as a door nail. I believe, since it was running fine when it first booted, that this may be a power issue (DC-DC Board). The DC-DC board is as far as I can understand, critical for the system as it produces all the other voltages from the 24V, as well as charging the battery)

Are any of you able to shed some light on this problem? Any known defect that are fixable without replacing the DC-DC board? Anyone have a spare DC-DC board for me?

Thanks,

F.G

 

[beachycove]

The trouble with these machines is that it takes a REAL COMMITMENT to troubleshoot them, even when you've got a parts machine to play with, because disassembly/ reassembly is not a trivial matter. The upshot is that almost nobody does it, and since almost nobody does it, there is scant experience to draw upon.

Mind you, the fact that it has been know to boot or to boot partially may be a good sign. Have you tried booting from an external drive/ different RAM?

 

[quantumii]

The disassembly and reassembly does not scare me, as I have been through worse many times before. Removing the ram and using the onboard only does no difference. It is possible to power the motherboard outside the case on this machine (connect only vital parts and the LCD) so there is no need to assemble everything each time I want to try stuff.

My main problem is that I have no parts, therefore I am stuck at square one. I still believe this is a DC board issue, as faulty voltages wil cause issues such as the ones I have mentioned. I will get myself a new DC board and then we will see if it will solve the issue.

 

[beachycove]

If I were you, I'd look into the possibility of simply getting another 12" powerbook with a broken LCD, and then do a swap. A screen swap with a later machine might even be possible, and the later, post-867MHz machines were much more capable. I have the last of the 12" powerbooks (1.5GHz) and I think it is just a great little thing, but the second last version was nearly as good (1.3GHz, I believe). They were also very reliable.

One day, I suppose, I will have to let it go, but not just yet....

You'd need to check to see whether a screen swap would actually be possible, as that I do not know.

 

[quantumii]

Hmmm, yeah.. A parts machine is indeed a good suggestion. I will investigate a little if the screen transplant is doable (should be?) or I will get a 867 mhz parts one, just to be sure.

I have been through the TI Book G4 hell many times, with incompatible screens, cases and other parts between the versions, so there might be some similar issues with the 12" alu one.

I do this mostly for the fun of it, it is not that I really _need_ yet another working mac, but the satisfaction of getting stuff back up and running is great.

 

[Byrd]

In the rare event it starts up, does it chime? And when running - does it work without issue/crashing? My 12" 867 has faulty 128MB onboard RAM which displayed similar symptoms before the RAM failed entirely. It now refuses to detect the onboard RAM, and "fails" its startup routine which results in no chime to express this fact. Apple's system profiler states the same.

The funny thing is - with 1GB stick of RAM installed, it works fine and has been used by my wife everyday for a couple of years now. When this issue occurred, I do recall reading some forum links whic reported similar issues with premature RAM failure in 867Mhz models, and how the RAM could be disabled by pulling up one of the legs of the onboard RAM.

I appreciate this may not be the issue, but thought it worth mentioning. The good thing about the 12" Powerbooks is that I believe motherboards are interchangable, so if you ever come across another cheap 1/1.2/1.5Ghz model you should be able to switch things around.

JB

 

[quantumii]

Thanks for the info. In the rare event of a chime, it stalls somewhere after the chime. No screen power on, no HDD activity.

As I said earlier, the machine always powers on, but does nothing else than spinning the HDD and making a click in the DVD drive. I could not even get a chime the last 10 times I tried.

I still strongly suspect the power board, as the DVD drive does not seem to get enough power to even do its power-on sound. Even if the RAM was faulty, the drive would initialize, as this is what it does when it gets the 5v it needs. If you try, for instance, to power a HDD with 5v but too little mA's, you will just hear a small "tick tick tick" as it tries to spin up, but fails because the current is too low.

The DVD drives behaves much like this. You hear a small "tick" and nothing more, and no chime. Just a "pop" in the speakers and a "tick" in the DVD drive as the power button is pressed.

Sometimes, usually after resetting the PMU a number of times, the DVD drive completes its init cycle, and then the macine stalls. If the chime appears, the same thing happens, but it never boots.

Oh, I should mention, the symptoms are the same if I power it from the battery or from the adapter (Home-made 24v one.)

Could a wasted PRAM battery cause all this issues? I think not, but you never know with these machines

 

[quantumii]

So, I finally got around to get myself a replacement DC-DC board, and guess what? No change. The problem has to lie elsewhere, but I do not know where to look for it. Maybe microcracks somewhere on the motherboard, I don't know.

I feel that I now have the below alternatives:

1. Throw it in the parts pile

2. Get another mainboard

3. Get another powerbook with a cracked screen

What do you guys think? It's not that I really need this machine, but you know how it is. It's a nice little machine after all.

 

[Byrd]

Time for the old "push down hard on various components on the motherboard to see if it boots" trick. Have come across a number of laptops recently - not Mac - with similar issues.

 

[quantumii]

Yes, I think so too.. Will dig it out again soon and see if that makes it wake up again

 

[techknight]

yup. the BGA solder has broken on one of the ICs. probably either the CPU or the chipset.

common problem on the IMAC G5s as well.