Black screen on Powerbook G4 12" and PowerMac G4 733

[bobesch]

First: Powerbook G4 12" display problem:
Need some help. Got a cheap 12" Powerbook G4 at the bay primarily for spare parts - sold as defect with stripes on the display. Came in in great shape with a decent battery and 1GB RAM brick.
I booted it with the help of my own working 12" Powerbook G4, which was set into Target-Disk-Mode. Display shows stripes. I could select and launch any firewire-booting drive and the grey Apple-logo appears. At the point, when the login-screen should come up, the screen turns black. At one occasion, when I booted the Powerbook with the help of the original installation DVD the display went black with flickering red spots all over the display. An attached external monitor shows the same picture.
Any idea how to localize the problem (GPU/InverterBoard/Cable)? I presume it's not a problem of the screen, since the attached external screen shows the same problem.
Here some pictures ...


Second: Powermac G4 doesn't boot
Then I've got that single core Powermac G4 733MHz (Digital Audio). Power supply is ok.
The ADC-connected Cinema Display get's power (and I can even put the PM into sleeping mode via display button too) but I can only hear the booting chime but the display stays black.

 

[eyoungren]

If you have the same graphical glitch on an external display as on the LCD then the problem is the graphic chip on the logicboard. And the only fix for that is a new logicboard.

 

[bobesch]

If you have the same graphical glitch on an external display as on the LCD then the problem is the graphic chip on the logicboard. And the only fix for that is a new logicboard.

Ah, thanks - that puts oil onto the fire of my fears...
I wonder, why the Powerbook shows the booting-screen but doesn't proceed into the login-screen anymore... The sellers pictures show a running Tiger with the same screen-artefacts I can see on the booting screen too.
Maybe any slight hope that it's only related to a loose cable or part, that got worse on the transport or because of the missing internal drive?
Anyway, I went for it for spare parts and a bit of a gold rush somewhere back in my mind...

 

[eyoungren]

Ah, thanks - that puts oil onto the fire of my fears...
I wonder, why the Powerbook shows the booting-screen but doesn't proceed into the login-screen anymore... The sellers pictures show a running Tiger with the same screen-artefacts I can see on the booting screen too.
Maybe any slight hope that it's only related to a loose cable or part, that got worse on the transport or because of the missing internal drive?
Anyway, I went for it for spare parts and a bit of a gold rush somewhere back in my mind...

Using an external display bypases any cable. So, there's no possibility that a loose cable would be the culprit.

Sorry to be the bearer of bad news. Perhaps someone has something else to add (hope) but AFAIK this is generally the issue when you encounter the same problem on an external display.

As to the user showing a working pic…well…it's eBay. Anything can be faked there. I'm not accusing the seller of faking anything, but it's possible that the Mac had been running for a while with this problem when the pictures were taken.

I rarely if ever shut off my laptops except if they crash or lockup. So any problems that could manifest would do so while the laptop had already been booted.

Just guessing here, I don't really know.

 

[bobesch]

I followed @Intell 's advice https://forums.macrumors.com/threads/12-powerbook-g4-screen-issues.1744095/#post-19224752 and booted into secure mode successfully.
Both PB-display and external monitor showed pin-striped screen artefacts.
Well, that confirms a higher grade problem (GPU/logic board).
Could be worse... I have a good working spare display-assembly then, a working optical drive, 1GM RAM, a spare keyboard, touchpad, decent battery etc
I hope, whenever my fellow little 12" Powerbook might fail, it's not the logicboard ...

 

[flyrod]

That sounds like the GPU. I worked on one that had similar problems. I found that if I took the logic board out and ran it with a plastic spring-clamp pinched on the GPU the problem would go away. This led me to believe the problem was a bad solder joint on the chip. I did the oven treatment (not exactly a re-flow) and that seemed to fix it.
[doublepost=1486320451][/doublepost]Oh the other mac, does the disk access light flicker like it's booting up? Can you log into it over ethernet with ssh or VNC? If so, a new video card could fix it.

 

[bobesch]

That sounds like the GPU. I worked on one that had similar problems. I found that if I took the logic board out and ran it with a plastic spring-clamp pinched on the GPU the problem would go away. This led me to believe the problem was a bad solder joint on the chip. I did the oven treatment (not exactly a re-flow) and that seemed to fix it.
[doublepost=1486320451][/doublepost]Oh the other mac, does the disk access light flicker like it's booting up? Can you log into it over ethernet with ssh or VNC? If so, a new video card could fix it.

Oh, thanks! Is it I can see some light at the end of the tunnel!?

What's exactly the difference between "oven treatment" and "re-flow"
This PB-logicboard will be my first occasion and attempt to try something like that (unfortunately a lot of my first attempts tend to end up in a mess ...)
It has certainly been a lot of work you had with your PB: disassamble - clip the GPU - assamble. Check result.
Then again fully disassamble - re-flow the logic-board and reassemble again... all with the vague chance to get the Book work again. Thumbs up!
I have to wait for sunny days to get enough courage for this attempt...
Again, many thanks!

 

[flyrod]

I think a re-flow is technically re-melting all the solder joints on the board in a controlled way, probably with flux, suitable tools etc. The oven treatment is the DIY version of a re-flow. There are various guides and write ups on how to do it. A lot of the intel mac books had flaky graphics chips, and one writeup said to get it running something cpu intensive and wrap it in a blanket. This was called a "re-flow" which is how I found it.

Anyway, what I did was take everything off the board like wires and ram, then popped it in a pre-heated convection oven at something like 150 degrees for several minutes. If you go much hotter you can actually melt solder and parts will start to fall off, plastic melt, etc. Meanwhile I heated up a little block of aluminum with a torch until it would melt solder. Then I opened the oven and set the block on top of the gpu, turned the oven off, opened the door slightly and let it all cool off. This is definitely a last ditch option that's not very scientific.

I've worked on a few 12" powerbooks, and they run fine laid out on a table. USB keyboard, external monitor, etc. If I'm testing something quick I just set a random heatsink on the CPU, short the power switch pins with a little screw driver, etc. It's all low voltage so it's not like you can get shocked or anything with parts and boards exposed. It seems like the best way to get a flaky computer to quit running is to put it all together with all the screws.

 

[Calum2]

- nvm

 

[weckart]

This problem of broken solder connections affecting part of the gpu seemed to be more common on the G3 iBooks. Another quick fix for them was a thin shim of metal between the foil over the gpu and the bottom casing. Don't think that works so well for the redesigned G4 versions. I just scoured eBay for a logic board for mine, as it was a last generation G4 so worth keeping. Any earlier version I would have broken up for parts.

There are a ton of baking how-to videos on Youtube etc if you want to go down that route but baking tends to be a temporary fix in order to get important data off notebooks before the gpu fails totally.

 

[bobesch]

Anyway, what I did was take everything off the board like wires and ram, then popped it in a pre-heated convection oven at something like 150 degrees for several minutes. If you go much hotter you can actually melt solder and parts will start to fall off, plastic melt, etc. Meanwhile I heated up a little block of aluminum with a torch until it would melt solder. Then I opened the oven and set the block on top of the gpu, turned the oven off, opened the door slightly and let it all cool off.
This is definitely a last ditch option that's not very scientific.
I've worked on a few 12" powerbooks, and they run fine laid out on a table. USB keyboard, external monitor, etc. If I'm testing something quick I just set a random heatsink on the CPU, short the power switch pins with a little screw driver, etc. It's all low voltage so it's not like you can get shocked or anything with parts and boards exposed. It seems like the best way to get a flaky computer to quit running is to put it all together with all the screws.

Aaah, great idea to use that little hot block of aluminium to apply heat directly onto the spot of the GPU.
That's truely scientific in my eyes - brilliant idea!
Well, have to think about your setting, to "operate at the open heart". I'm less than a novice, when it comes to electronics.
"It seems like the best way to get a flaky computer to quit running is to put it all together with all the screws." defintely made me laugh out loud! YMMD Thanks!
[doublepost=1486507214][/doublepost]

- nvm

ho humm, what'S your message?
[doublepost=1486508551][/doublepost]

This problem of broken solder connections affecting part of the gpu seemed to be more common on the G3 iBooks. Another quick fix for them was a thin shim of metal between the foil over the gpu and the bottom casing. Don't think that works so well for the redesigned G4 versions. I just scoured eBay for a logic board for mine, as it was a last generation G4 so worth keeping. Any earlier version I would have broken up for parts.
There are a ton of baking how-to videos on Youtube etc if you want to go down that route but baking tends to be a temporary fix in order to get important data off notebooks before the gpu fails totally.

The PB-G4 sports another architecture compared to the iBook-G3.
The GPU sits face up directed to the keyboard and is covered by the common heatsink for CPU and GPU.
There's a thermal-pad between GPU and the heatsink, which bufferes pressure, so that the GPU might get relatively 'loose" compared to the CPU, which is firmly pressed against the heatsink by to screws sitting next by.
It might be possible to fit a copper-plate between heatsink and GPU to add more pressure (the same way you've mentioned about G3, GPU "and the thin shim of metal between the foil over the GPU and the bottom casing"
But first I'm gonna try oven and aluminium-block... - even it might be only a temporary fix or even fail.
Today, I have no fear of any need to recover data by sacrificing oven-treatment, since there's an armada of old PPC hardware, which will be lucky to borrow any homeless harddrive/mSATA to continue work.