iMac G5 20' Red Green Blue Flash Screen of Death

[gokhantonyukuk]

Hello. I bought an very cheap unworking iMac G5 20'. The problem is It doesn't boot at all. Screen flashes Red Green Blue Gray White & all over again after the opening sound. Also fan working very loudly. I tried PRAM/NVRAM reset(which didn't helped) & Target Disk Mode(not even worked).
Some people say it could be motherboard, graphic or something else. Do you know any idea how to fix it? Is there any way to I can repair it? If anyone helps I would be grateful.

 

[Raging Dufus]

Chances are real good you've got failed capacitors on the logic board, a very common problem with iMac G5's. If so, the only way of fixing it is to replace them - which is a difficult job even if you have some soldering skills. If you don't have skills, search around this forum and elsewhere on the Internet for "iMac G5 bad caps", and you'll find plenty of info about the problem and how to fix it. If it looks like something you're up for, no harm in giving it a try - if it doesn't work you're no worse off.

BUT!...all that being said, the very first thing you should do is open the machine up and clean any crud outta there. Eliminate any cooling problems by making sure the fans and heat sinks are not choked with dust or encrusted with other stuff. Cooling problems are enemy #1 to G5's. Then, make sure the RAM is seated properly, check for loose connections, etc. Do the basics first and see if any of that doesn't improve your situation.

 

[gokhantonyukuk]

Chances are real good you've got failed capacitors on the logic board, a very common problem with iMac G5's. If so, the only way of fixing it is to replace them - which is a difficult job even if you have some soldering skills. If you don't have skills, search around this forum and elsewhere on the Internet for "iMac G5 bad caps", and you'll find plenty of info about the problem and how to fix it. If it looks like something you're up for, no harm in giving it a try - if it doesn't work you're no worse off.

BUT!...all that being said, the very first thing you should do is open the machine up and clean any crud outta there. Eliminate any cooling problems by making sure the fans and heat sinks are not choked with dust or encrusted with other stuff. Cooling problems are enemy #1 to G5's. Then, make sure the RAM is seated properly, check for loose connections, etc. Do the basics first and see if any of that doesn't improve your situation.

Thanks, I've checked it as you said. It seems like a hard job for me but I can try with some help.

 

[gokhantonyukuk]

When I open the case I realized someone tried to pull out screen cable with wrong screw, It was hard to unplug even I had correct ones. I wonder if this problem could be cause of bad cable?

 

[Raging Dufus]

someone tried to pull out screen cable with wrong screw

I'm not clear on what you mean here, but if the inverter/display cables and/or connectors at either end have been damaged, that would definitely cause problems.

 

[gokhantonyukuk]

I'm not clear on what you mean here, but if the inverter/display cables and/or connectors at either end have been damaged, that would definitely cause problems.

I meant screws which hold the monitor cable were damaged. Now I need another display cable to confirm if it's the problem. Ty

 

[Traace]

That error usually means screen still gets power but no image signal

Indeed, maybe just a cable change can fix it

 

[gokhantonyukuk]

First of all, thanks for the help. I managed to remove LCD Panel without breaking anything. What I saw is pretty interesting: LCD Cable just plugged off & there was no Hard Drive & no bracket. Luckiy I got an empty Hard Disk(which I was trying to sell because I wasn't use it). It was hard to put HD without bracket, I used mac pro hard drive bracket & some silicon to put it. Plugged in LCD cable. And it seems everything working. Now I'm using Target Disk Mode to format it(only problem is fans working loudly in Target Disk Mode, I hope it's the reason). If I manage to fully format & make it work I'll inform again.

 

[gokhantonyukuk]

I managed to install Leopard 10.5.8. Almost Everything seems working: Wifi, Bluetooth, iSight, Sound, LCD, DVD player, usb & firewire slots...

There are slight problems. For example Ram runs at 3200 bus speed(400mhz) but it should be DDR2 667mhz(I've learned this model comes with 533mhz built in 512mb ram. So I'll try to change 2Gb 667mhz ram with 533mhz).

Other problem is heating, especially on using web. I couldn't find any software to speed up fan rpm yet(When I searched it seems G5 imacs heating is a common problem).

It worked unexpectedly fine for now. I was lost hope for a moment when I saw there is no Hdd in case: I Thought lots of parts missing. Anyway, it's working now. I'm sharing working picture. Thanks all.

 

[Traace]

These are always loud and hot because they run G5 CPU.
(There is a reason why Apple never managed to produce Notebooks with such a CPU )

AFAIK there is no software to control fans in a iMac G5, however there is a Application called "FastAndSlow" it can throttle CPU so you get less heat from it means lower fan speed.

 

[Raging Dufus]

I managed to install Leopard 10.5.8. Almost Everything seems working: Wifi, Bluetooth, iSight, Sound, LCD, DVD player, usb & firewire slots...

There are slight problems. For example Ram runs at 3200 bus speed(400mhz) but it should be DDR2 667mhz(I've learned this model comes with 533mhz built in 512mb ram. So I'll try to change 2Gb 667mhz ram with 533mhz).

Other problem is heating, especially on using web. I couldn't find any software to speed up fan rpm yet(When I searched it seems G5 imacs heating is a common problem).

It worked unexpectedly fine for now. I was lost hope for a moment when I saw there is no Hdd in case: I Thought lots of parts missing. Anyway, it's working now. I'm sharing working picture. Thanks all.

RAM is generally interchangeable within groups; i.e., PC2-3200, PC2-4200, PC2-5300 will all function in a PC2-5300-based system because they are all within the DDR2 group. However, the lowest speed of what you have installed is the speed your entire stock of RAM will use. In other words, if you have a PC2-3200 (400MHz) module - even just one - installed with PC2-4200 (533MHz) modules, the whole set will run at the lower speed of 400MHz. That's probably what's going on here.

As far as the heating issues, as @Traace said, get used to that with G5's. One thing you should probably do, however, if you didn't already do it the first time you were inside the machine, is to remove the heatsink, clean it and the CPU surface of any old thermal paste, and apply a fresh coat. Fresh thermal paste will go a long way toward keeping your G5 cool.

 

[Traace]

As far as the heating issues, as @Traace said, get used to that with G5's. One thing you should probably do, however, if you didn't already do it the first time you were inside the machine, is to remove the heatsink, clean it and the CPU surface of any old thermal paste, and apply a fresh coat. Fresh thermal paste will go a long way toward keeping your G5 cool.

Oh great advice

I really need to do that too. But to change thermal paste on a Rev. A (early) iMacG5 AFAIK... well...

1. Open backside
2. Remove HDD
3. Remove Fans
4. Remove Inverter, Speaker whatever
5. Remove PSU, Drive....
6. Remove middle frame from front assembly
7. Disconnect Display from Mainboard
8. Pull off "G5" CPU shield to access some screws
9. Pull out entire Mainboard and flip over to access more screws
10. Remove Heatsink & remove older paste
11. Apply new paste
12. Put all back together


Its not... simple (but dont worry! Rev c. is more easy)

 

[DeltaMac]

RAM is generally interchangeable within groups; i.e., PC2-3200, PC2-4200, PC2-5300 will all function in a PC2-5300-based system because they are all within the DDR2 group. However, the lowest speed of what you have installed is the speed your entire stock of RAM will use. In other words, if you have a PC2-3200 (400MHz) module - even just one - installed with PC2-4200 (533MHz) modules, the whole set will run at the lower speed of 400MHz. That's probably what's going on here.

As far as the heating issues, as @Traace said, get used to that with G5's. One thing you should probably do, however, if you didn't already do it the first time you were inside the machine, is to remove the heatsink, clean it and the CPU surface of any old thermal paste, and apply a fresh coat. Fresh thermal paste will go a long way toward keeping your G5 cool.

All good tips - but the OP's iMac (PowerMac12,1) also called an iSight iMac, has only the one slot (with 512MB soldered in). Looks like the OP got that part figured out: maxed out to 2.5 GB!

 

[Raging Dufus]

All good tips - but the OP's iMac (PowerMac12,1) also called an iSight iMac, has only the one slot (with 512MB soldered in). Looks like the OP got that part figured out: maxed out to 2.5 GB!

I realize that, but even though the soldered-in 512 MB module is 533 MHz, if the stick in the expansion slot is 400 MHz - the system will downclock ALL of the RAM to run at the slower speed.