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PowerMac G4 (very) weird problem - HELP ME!

pochopsp

pochopsp

macrumors 6502
Original poster
Apr 6, 2016
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Napoli, city of sun and pizza!
Hi guys! My PowerMac G4 is having a weird problem, but I am pretty sure you'll help me identifying this problem and fixing it.

Specs are: PowerMac G4 MDD 1.25 GHz single core (PowerMac 3,6), 1 MB cache L3, 4 sticks of 256MB of RAM to get 1 GB (but sometimes showing 768 MB in "about this Mac", after a reboot again 1 GB), video board is the stock Ati Radeon 9000pro and it has two HDDs. One is for OS X Leopard and the other one is for Debian (so I also have Yaboot installed as bootscreen).

The problem is: sometimes, when I have it turned on for at least a few hours and have a screensaver running in the background, or/and with music playing using Vox (but I think it'd be the same with any other player), or it is turned on for a few time but I am watching some video on Youtube on webkit, suddenly a weird noise like a BZZZZTTSS, BZZZZ (like radio interferences) comes from the speaker, the Mac stucks, the spinning beachball appears and/or the message saying I have to reboot (the one in the attached pic) appears.

I must tell you that I have never done any manteinance task (such as clean the inside, replace the thermal paste, replace parts etc...). Is it related to manteinance, RAM, or what???

The Mac works normally and well for the most times I use it, in fact I am typing this post on it.

Thanks everyone in advance :)
 

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If it sometimes shows 768MB when there is actually 1GB I can pretty guarantee it's a bad memory stick. Kernel panics are very common for this.

Here's what you need to do... take out one of the 4x 256MB sticks and run the system normally. Do this with each stick until the issue stops. When it stops then whatever stick is not installed was the culprit, and should be recycled.

As for the audible buzzing. it sounds like it's a grounding issue. Not as in power grounding but as in audio grounding. There are specific little wires that you can buy which attach to a metal part of the case to alleviate this. I'm not sure what they're called though.
 
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pochopsp said:
So you say RAM it's the problem. I have another hint for you... When I try putting it in sleep mode, it gets into sleep mode and then instantly turns itself on again.
Click to expand...

Could also be PSU issues. My first 1.25 MDD was cranky running 2 HDDs - removing one seemed to cure the problem for a while - presumably less power draw...I gave up on that particular one!
 
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Dronecatcher said:
Could also be PSU issues.
Click to expand...

I agree.

pochopsp said:
The problem is: sometimes, when I have it turned on for at least a few hours and have a screensaver running in the background, or/and with music playing ... or it is turned on for a few time but I am watching some video ... suddenly a weird noise like a BZZZZTTSS, BZZZZ (like radio interferences) comes from the speaker, the Mac stucks, the spinning beachball appears and/or the message saying I have to reboot...
Click to expand...

pochopsp said:
When I try putting it in sleep mode, it gets into sleep mode and then instantly turns itself on again.
Click to expand...

These are all potentially power-related issues (the last one, almost certainly). Does your MDD still have the original power supply unit?

Years ago I too experienced something similar with my MDD, a few weeks before the PSU failed outright. If yours is doing the same thing, you can expect that one day it will simply "die", and that will be the end of it (the PSU, not the MDD). All MDD's were shipped with failure-prone PSU's; frankly, if yours is still original it's remarkable that it's worked this long.

There are alternatives. I replaced my MDD's original PSU with an ATX unit; many others have also had success going that route. If you want to read more about that, check out this thread.

But before you do that, it's definitely worthwhile (and a good bit cheaper in time and effort) to try out @timidpimpin's and @Dronecatcher's suggestions. Keep in mind, though, that often a failing PSU causes the failure of other components before it goes. If your symptoms persist, or return, then it's probably time to give the PSU a look.
 
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Yeah, it still has its original power supply unit. However recently when the problem occured, every time I rebooted it immediately after, the Mac showed 768 MB in "about this Mac". So it could be both RAM and PSU problems. I have two HDDs, the other one is for Debian, but I don't use it so often so, I could disconnect it. I have yaboot installed, will I have problems if I do so? For RAM, how to know which stick is the problem? Do I have to try them one by one?
 
pochopsp said:
So it could be both RAM and PSU problems.
Click to expand...

I agree. Sometimes the latter can cause the former. Power issues can affect everything on your computer.

pochopsp said:
For RAM, how to know which stick is the problem? Do I have to try them one by one?
Click to expand...

Your Power Mac will not boot without a stick of RAM in memory slot #1. I forget which one that is on a MDD, but it's easy enough to determine. Remove all the RAM except one stick, and leave that one in the first, or last, memory slot. If it boots, you've found slot #1; if not, then switch the stick to the slot at the opposite end of the row.

Once you've figured out which slot is #1, then try each stick of RAM that you have, one at a time, in that slot; trying to boot each time. Check the memory info in System Profiler each time to see that the stick is registering correctly - proper amount of MB and proper speed. Eventually you'll find one that either won't allow the Mac to boot while it's in slot #1, or doesn't register correctly if it does boot - that's a bad stick of RAM.

It's also possible that one of your RAM slots is failing. To find out, use two sticks of RAM that you've already established are good (by doing the above); leave one in slot #1, and switch the other between slots 2, 3, and 4, rebooting each time. Check System Profiler as described above. If a known-good RAM stick doesn't register properly in slot 2, 3, or 4, then you have a failing memory slot.
 
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Ok guys. I've ran MemTest trying all four 256 MB RAM sticks I have... No errors so far. But I discovered that only the first and the last are working well. The two ones in the middle sometimes fail to read my RAM sticks. So I took out my two sticks in the middle and left only the ones in the first and the last stick. As result the system seems a lot more stable but I only have 512 MB of RAM now, which is very few memory for Leopard. The "sleep problem" is still there, when I try to put the Mac in sleeping mode from the Apple menu it goes into sleeping mode and then it turns on again by itself after only a second.

So I was wondering:

1) which 512MB RAM sticks do I have to buy? I mean the exact model for MDD PowerMac G4 so I can look for them on eBay and with two 512MB sticks I'll have 1 GB again.

2) is the sleeping problem 100% related to the PSU or could it be other things also? If it is related to PSU, where I can buy a new one for my MDD?

Thanks a lot guys
 
pochopsp said:
Ok guys. I've ran MemTest trying all four 256 MB RAM sticks I have... No errors so far. But I discovered that only the first and the last are working well. The two ones in the middle sometimes fail to read my RAM sticks. So I took out my two sticks in the middle and left only the ones in the first and the last stick. As result the system seems a lot more stable but I only have 512 MB of RAM now, which is very few memory for Leopard. The "sleep problem" is still there, when I try to put the Mac in sleeping mode from the Apple menu it goes into sleeping mode and then it turns on again by itself after only a second.

So I was wondering:

1) which 512MB RAM sticks do I have to buy? I mean the exact model for MDD PowerMac G4 so I can look for them on eBay and with two 512MB sticks I'll have 1 GB again.

2) is the sleeping problem 100% related to the PSU or could it be other things also? If it is related to PSU, where I can buy a new one for my MDD?

Thanks a lot guys
Click to expand...

1) Your model Power Mac supports PC2700 333MHz DDR SDRAM in 184-pin DIMM's.

PC3200 184-pin DIMM's will also work, your memory controller will just clock them down to PC2700 speed.

2) The sleep problem is likely related to the PSU but not necessarily; it could be an issue with your logic board. The best source for another PSU would be eBay, but I personally wouldn't replace one bad MDD PSU with another original. They're all bad, really; it's only a question of when they will fail.

I personally have a policy of replacing every MDD PSU I encounter with an ATX unit. If you're interested, check out this thread (which I also linked in an earlier post). There are a multitude of other resources available with a quick web search.

As for your logic board, I think I would replace that too. Either you have a couple of failing memory slots, or the memory controller itself is failing. The only remedy for either of those is a logic board swap. This is true regardless of whether or not you need a new PSU.

I really hate to say this, but it might be time to just throw in the towel on this Power Mac.
 
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