Blank screen on reboot after frozen screen

I also swap my hard drive with my old one and reinstall from scratch OS X 10.4. Same problem.

Also, I tried install the Factory DVDs containing all the original software incluing OS 9. I get the message when I boot with the DVD that :

"The Built-in memory test has detected a problem with cache memory. Please contact a service technician for assistance."

Tks for the quick reply.

I put the good hard drive in, try to clean any dust in there near the cpu and stuff. Removed then placed back the rams.

At some point I had this: I checked System Profiler, under memory my two dimms are good. However, under Diagnostic, I also get a note that the result failed and the type is external cache. Also, OS X is starting to struggle to resync the date that I basically reset to Dec 31 1969. Same kind of issue at startup.

Later on, after a bunch of restart and shutdown, the Diagnostic could not find anything wrong. The PowerBook seems to start even after a shutdown, without a system reset, although I see that it is really looking for the OS as it shows a question mark folder icon. It finally, after 1 sec, finds it and start. I redid a Hardware Test using the factory DVD and as before, all elements PASSED, including Memory and Logic Board. Even the OS 9 Factory DVDs would install if I chose to as it does not tell me that there is a problem with cache memory like it did before.

I was just using it... at some point, when I was doing more intense task, it froze again. However, it reboots this time without a hardware reset. Then again, another time, froze but I had to reset the hardware to reboot.

This is strange, not consistent.

Powerbook Ti G4 Mac OS X (10.4.7)

Tks for your advices.

The only thing still bothering me, other than the fact that I will have to shell a lot of money on a new portable, why is it that the powerbook can still function ok? It has been one day since I have not restarted or shutdown. As long as I don't do to much at the same time, things are running ok. I fixed my date to avoid some crazy things going on with iCal. Sometimes, a simple things like extracting a .SIT can take a long time, which is abnormal. L2 cache is what is my external cache memory? Why is it that it can still function? Are things risking to go downhill from now one, including a major short circuit at some point? Tks.

Where can I find information regarding the location of the external cache? I doubt I can find a new board or processor cheap, perhaps from a powerbook like mine that died from another cause (busted screen, hinges, etc...)

I think I have the powerbook G4 release prior to the gbit version, since I bought in in Sept 01. Here is what I found on it ( http://support.apple.com/specs/powerbook/) :

Processor and memory
400- or 500-MHz PowerPC G4 processor with Velocity Engine
1MB backside level 2 cache on processor module; 200- or 250-MHz dedicated 64-bit backside bus
100-MHz system bus
Integrated floating-point unit and 64K on-chip level 1 cache (32K data and 32K instruction)
128MB or 256MB of PC100 SDRAM; two SO-DIMM slots support up to 1GB

Powerbook Ti G4 Mac OS X (10.4.7)

It is funny. If you call Apple directly, they tell you thet are only able to help you on the software side. For hardware, you have to go to an authorized service dealer, which asks to bring the laptop in to check it, when they could eye ball the problem based on symptoms you tell them, from rigorous do it yourself troubleshooting.

Tks for the link. So if I understand correctly, the logic board contains an all in one (video cards, motherboards, I/O, processor, etc...). You break it, you change it all. In my case it would be a 300$ part. If I take into account that my battery does not even last 1 min since two years ago, It is perhaps time to use it moderatly and start thinking about a 1500$ MacBook which is so much faster, even with the not so great graphic card from Intel. Since you mentioned in another post that you cannot disable the external memory cache in powerbook G4, I can only hope it stays at Failed so that I don't get crash freeze. It is slower than usual for sure. I will see how patient I am. I keep my pbook on at all time, on sleep mode and restart. That way, my clock stays ok and I can reboot. A shutdown will require most of the time a logic board reset. Tks for the help.

Powerbook Ti G4 Mac OS X (10.4.7)

Since my last post and successful restart to use the PowerBook on life support, I have not shut down the Mac. I only restarted and used sleep mode to keep power on the logic board component.

I know for a fact that my L3 Cache is not working anymore. Replacing it means a new logic board, so I bought a new mac. I still want to keep this baby alive.

So the solution is to to a simple reset of the Power Management Unit (PMU). The step by steps are explanined here:
http://support.apple.com/kb/HT1431#faq8

After reseting, the OS boots but is totally lost with a computer clock set at March 14th 2001. A quick setup in the Preferences to set it up manually and a restart, then no shut down keeps the PowerBook alive. Auto setting the time does not seem to work.

*My question is there a real link between L2 Cache and PMU?

*Would changing the button cell battery on the logic board avoid the PMU issue?

Something is wrong on the logic board. Nothing worth repair when you can get better new.
I simply press the Resest button behind the powerbook and it start again. It does not always loses the clock time.