G4 MDD shutting down issues

[tidymeup]

Hi All,

I am a long time Mac user and was feeling somewhat nostalgic, the wife says I am having a midlife crisis.

So I bought myself some old G4 PowerMac's, the one that interests me is the G4 MDD dual 1.4 ghz.

I gave it a little clean and fired it up, and it worked perfectly, however, on my second play with the machine not everything was quite so good.

As soon as the machine booted into OSX it would shut down and leave the power button flashing, so I started searching and reading.

So far I have changed the battery, reset the PMU, cleared the p ram, applied new thermal paste, and changed to an ATX power supply.

I thought this would have fixed it and started to install Tiger, part way through and it turns off, this time completely with no flashing power button.

it's like clockwork though pretty much the same length of time until it shuts down, the fan is always on full, though it wasn't as loud as it is now the first time I used the machine.

Is there anything that I am missing?

Thank you.

 

[MrFahrenheit]

Welcome to the forum! Have you tried reseating the RAM and trying different DIMMs (if you have), or reducing the number of DIMMs to test each one?

 

[Phipli]

Hi All,

I am a long time Mac user and was feeling somewhat nostalgic, the wife says I am having a midlife crisis.

So I bought myself some old G4 PowerMac's, the one that interests me is the G4 MDD dual 1.4 ghz.

I gave it a little clean and fired it up, and it worked perfectly, however, on my second play with the machine not everything was quite so good.

As soon as the machine booted into OSX it would shut down and leave the power button flashing, so I started searching and reading.

So far I have changed the battery, reset the PMU, cleared the p ram, applied new thermal paste, and changed to an ATX power supply.

I thought this would have fixed it and started to install Tiger, part way through and it turns off, this time completely with no flashing power button.

it's like clockwork though pretty much the same length of time until it shuts down, the fan is always on full, though it wasn't as loud as it is now the first time I used the machine.

Is there anything that I am missing?

Thank you.

The sad truth is that G4 PSUs are... Not aging well. The symptoms you describe are possibly a sign of a power supply on the way out.

A power supply recap might bring it back, especially as it still mostly works.

 

[MrFahrenheit]

The sad truth is that G4 PSUs are... Not aging well. The symptoms you describe are possibly a sign of a power supply on the way out.

A power supply recap might bring it back, especially as it still mostly works.

They said they changed the PSU to an ATX one though.

 

[Phipli]

They said they changed the PSU to an ATX one though.

Ah, so sorry. You know, I read it twice to see if they had and somehow missed it both times. I think I was skimming for the word "recapped" too much.

Weird, that is just about /the/ bad PSU symptom though? One of mine powers on for 3 seconds and then shuts off. But, it works fine from an ATX conversion.

So far I have changed the battery, reset the PMU, cleared the p ram, applied new thermal paste, and changed to an ATX power supply.

Did you rewire the ATX to match the Mac's pinout?

 

[tidymeup]

Ah, so sorry. You know, I read it twice to see if they had and somehow missed it both times. I think I was skimming for the word "recapped" too much.

Weird, that is just about /the/ bad PSU symptom though? One of mine powers on for 3 seconds and then shuts off. But, it works fine from an ATX conversion.

Did you rewire the ATX to match the Mac's pinout?

Hi,

Yes I rewired it to match the pin outs but of course missed out the +25v for ADC.

I was gutted as I thought it would fix the issue, spend bloody ages messing with them pins.

 

[tidymeup]

Welcome to the forum! Have you tried reseating the RAM and trying different DIMMs (if you have), or reducing the number of DIMMs to test each one?

I have messed about with the DIMMS, though I might try this again.

I got three beeps which I assumed was bad or incorrectly seated memory. Took them all out and got a single beep. So stuck with just a single which seemed to work fine.

 

[tidymeup]

I don’t know if this link will work, it’s a video of what’s happening.

Also swapped some dimms aroud to see if it makes a change.

It’s mental noisy!
https://share.icloud.com/photos/0485xeYj5HcEwikcrMRl0w6pQ

 

[tidymeup]

So after some more testing I am sure this is heat related, I have double checked the thermal paste and reapplied, it was making good contact.

Though the CPU daughter card does have a bow in it, I guess from years of having a cooler pushing against it, perhaps this could be causing uneven contact.

When the machine is first turned on from ambient room temperature it will run for 10 minutes, turned straight back on it lasts just 5 minutes

After a shot break it will stay on for 7 minutes, but turned back will only run for 4 minutes.

This keeps getting progressively worse with louder and louder fans.

Has anyone else notice a bend in the CPU daughter card?

 

[cheesestraws]

I know little about G4s, but I agree that in your position I'd assume that was heat related too.

 

[CircuitBored]

So after some more testing I am sure this is heat related, I have double checked the thermal paste and reapplied, it was making good contact.

Though the CPU daughter card does have a bow in it, I guess from years of having a cooler pushing against it, perhaps this could be causing uneven contact.

When the machine is first turned on from ambient room temperature it will run for 10 minutes, turned straight back on it lasts just 5 minutes

After a shot break it will stay on for 7 minutes, but turned back will only run for 4 minutes.

This keeps getting progressively worse with louder and louder fans.

Has anyone else notice a bend in the CPU daughter card?

My experience with MDDs is limited to just two machines but I've never seen a warped CPU card in one. That said, I have seen warped a warped CPU card in a Quicksilver that had a dead fan and overheated itself to death. Please can you post a picture of the bend in your CPU card? Once a card like that warps beyond a certain point it becomes nigh-on impossible to repair. Depending on how badly your card has warped, you may be able to coax it back into life with a hot air reflow but that's seldom a permanent fix.

That said, the warped CPU card could be a red herring, depending on how bad it is.

The "three beeps" at boot is indeed a RAM issue. Here's a list of PowerMac beep codes for completeness' sake:

1 beep = no RAM installed
2 beeps = incompatible RAM types
3 beeps = no good banks
4 beeps = no good boot images in the boot ROM (and/or bad sys config block)
5 beeps = processor is not usable

The good news is that, since you're not getting the 5 beeps on a "hot" reboot, your CPU may well be totally fine. You should definitely test all your RAM in a different system if possible. Spray some contact cleaner in the RAM sockets for good measure. Contaminated pins become more problematic as they heat up.

One thing you could try to test your theory that it's a thermal issue is using a heat gun/hairdryer to warm up the CPU heatsink a bit and see if it fails to boot. On the other end of the thermal scale, try running the MDD with the door open and a large fan pointed directly at the heatsink to keep it as cool as possible and see if that makes a difference.

After that and troubleshooting the RAM you've pretty much narrowed it down to a logic board issue. Since the PSUs in the MDD are known for having extremely bad caps it's not out of the question that the logic boards are affected too. Sadly there's not much you can do to test your logic board besides finding a working MDD to swap it into.

 

[demik]

MDD (and some Quicksilvers) are kinda known to cook themselves to death.

Usually the slots (RAM, AGP, CPU) start having issues which can lead to similar issues. It can happen with the CPU board as well but the logic board is more likely.

Can you try some redneck cooling (like portable house fan + open case or something) and see if it's any better ?

 

[Nixontheknight]

MDD (and some Quicksilvers) are kinda known to cook themselves to death.

Usually the slots (RAM, AGP, CPU) start having issues which can lead to similar issues. It can happen with the CPU board as well but the logic board is more likely.

Can you try some redneck cooling (like portable house fan + open case or something) and see if it's any better ?

had the same thing happen with an MDD, overclocked and overvolted it and it wouldn't power on

 

[tidymeup]

The bend in the card isn’t much really after looking at it.

Cooler held against the heat sink makes no difference.

Fans on a hot boot come on right away on full and try to throttle back but only for a few seconds.

Frustrated!

 

[CircuitBored]

had the same thing happen with an MDD, overclocked and overvolted it and it wouldn't power on

@tidymeup it would actually be a prudent move to check that no one has tried to overclock your MDD's CPU or system bus previously and done a bad job of it.

You can check your multiplier settings using the info on this webpage.

 

[tidymeup]

I will check out the page, interesting info thank you.

Though this evening thought I would check to see what the CPU’s are doing.

Wow one gets really really hot really quickly.

I would imagine that this is the problem, not perhaps the brightest way you check with a finger and no cooler. But without anything to hand it may be an indicator.

I will keep an eye out for a cpu card to test, will any DP card work from a similar machine, I would imagine the lower end cards might need the bus speed altering?

Thank you all for the help with this.

 

[tidymeup]

Another update, I have found a CPU daughter card but it's only 867 MHZ, I can match the bus speeds easily by changing the resistors. but should I resist the logic board down or the CPU up?

It's not entirely clear if I will have to alter the voltages because it will need more current to be overclocked.

 

[GRudolf94]

It's a tad late to reply to this post, but you should change the card to match a 167MHz bus.