G5 Dual Processor Problem

[mac2geezer]

I have a 2.0GHz dual processor G5, (June 2004, 8 Ram slot model), that will not boot unless I heat the MB area around the Ram slots with a hair dryer for about a minute, then it boots and runs fine. Attempting to boot cold, the front panel light flashes 3 times, indicating a Ram problem. I've tried all the slots in different combinations, tried different Ram that tests good in other machines, tried the eraser on the contacts trick...the only thing that works is the heat. Inspection with a magnifying glass reveals nothing I can see out of the ordinary.

My conclusion at this point is a flakey component on the logic board. If anyone has other ideas/things to try I would love to hear.

 

[MacJunky]

Bake! Bake! Bake!





(the mobo, that is)

 

[mac2geezer]

Bake! Bake! Bake!

A joke?? If not, elaborate please.

 

[Andrevas]

I think what he's suggessting is that you have a microfracture problem with solder joints on the board somewhere there and that baking the board in the oven for a short time might fix it. sounds plausible to me just need to keep the temp low and duration short obviously.

 

[mac2geezer]

I think what he's suggessting is that you have a microfracture problem with solder joints on the board somewhere there and that baking the board in the oven for a short time might fix it. sounds plausible to me just need to keep the temp low and duration short obviously.

That's what I thought but would like a little more info about bake temp and duration, if available.

Also, I'm told that by replacing the MB I would need to calibrate the fans or they would run at full speed. Can anyone confirm this, and if true, point me to the calibration software. I have not been able to find anything relevant on Apple's site or on InfoMac.

 

[beachycove]

The calibration software can actually do a range of things, including running a lengthy series of tests on the machine — along with calibrating the processors. It is likely something you need in your situation now, never mind if and when you transplant a logic board.

If you google "ASD 2.5.8", it will come. As far as I know, that version should work with all dual G5 machines, or at least, it certainly does up to the middle of the series (I have used it on my dual G5s). It's just the standard service tool of the time for a range of hardware, and is not ultra-specific to a particular G5.

 

[mac2geezer]

Thanks for pointing me toward ASD. Obtained a copy and after some effort was able to get the G5 to start up enough to load ASD and ran it far enough to see that there's no need to calibrate the fans, at least at this point (no surprise since the CPU's haven't been removed from the MB). However, when I try to run the hardware tests the system freezes solid shortly after test start and the fans slowly increase to max speed.

There were other problems when I was able to boot from the HD, including KP's and other freezes. If I can't find a replacement MB for a reasonable price it will probably be time to part it out. Sigh!

 

[beachycove]

You might try removing the l.b. and refreshing the solder joints on the ram slots, which presumably go through the board to the other side. I don't know if that is the idea behind baking the thing or not — never heard that one before — but the whole heat and RAM business makes me think that cracked solder is the culprit. Maybe someone pushed too hard on a RAM chip.

The G5s look intimidating but they are really not that hard to take apart. You need a few tools, with which the processors come out and go back in just fine. There are some how-to guides out there describing the steps, though relating to servicing the liquid cooled units (the screws and so forth are in the same positions with the air cooled ones).

I had one of mine mostly apart in under half an hour — and fixed and working when it went back together. So it can be done.

 

[mac2geezer]

I had one of mine mostly apart in under half an hour — and fixed and working when it went back together. So it can be done.

Well, I was not nearly that fast but did get it disassembled and back together with only one goof that I was able to fix. Inspection of the logic board back side showed no flaws that I could see with a magnifying glass. Attempting to resolder the ram slot pins would be a formidable job; there are hundreds of them in very close proximity and well beyond my solder skills. After putting it back together the symptoms are the same so at least I'm no worse off than before.

It appears that another logic board is indicated.

 

[MacJunky]

Bake before replace! If you are just going to toss it then you have noting at all to lose. Go read up on baking laptop mobos, graphics cards, xboxes, etc and give it a shot!

It is dead right now anyway. Worst that can happen is that you kill it more, best that can happen is that you fix it.

 

[johnklos]

In lieu of baking or soldering, you could also get a heat gun and just melt all the solder joints at once. With foil covering plastic and covering other parts, you should be able to do all the RAM slots in just a few minutes.

Baking works well, but you have to be VERY careful - getting things hot enough to allow solder to flow means the slightest nudge could dislodge components. Gravity can do that for you if you're not careful, too.

 

[MacJunky]

Unfortunately plenty of people burn their boards with heat guns because they do not know what they are doing or do not have temperature monitoring goodies and such. At least an oven is a bit more of a closed environment that you can place (common oven)thermometers in to keep an eye on the temperature and you do not have to manually operate anything but a dial or two. I still believe that baking is the mildly more idiot-resistant method.

Granted, in the long term if you want to get into this sort of thing you will develop skill with and require a heat gun. It is also a more useful tool for part-swapping than an oven or even some of the soldering irons people have, I am not hating on em. They have their (large) place; they are very useful.

On a side note, if you are melting the plastic then you are a liiiittle too hot. (actually way too hot, this is quite doable without burning paperish stickers on the board and without melting plastic.. unless apple used real shit.)

Having said all that, I think the biggest problem with baking, most people do not want to use their kitchen oven and many people live in rental homes/apartment that are not wired with handy 230V plugs on the exterior or in the garage(this is north america I am talking about here).

Even if they do, if they want to troll around for a free or cheap oven that someone put out on the side of the road, they would kinda still either need a truck or need to know someone with a truck to bring it home.. Toaster ovens may be ok for video cards, but most motherboards do not fit in them.

 

[mac2geezer]

Well, I found a used logic board on eBay for a reasonable cost and replaced the malfunctioning board. The board came in a trashed case with a DVD drive and some of the fans, so I have a few other spare parts now. And the G5 is working great now.

I may try the baking idea on the old board just to see if it works in this case. Some commentators on other forums were, shall we say, skeptical.

Thanks to all for the replies to my original query.

 

[Byrd]

I am very skeptical of the "baking idea"; as much as enjoy repairing faulty computer gear, this is where I cross the line! PCBs contain very toxic chemicals, and baking these is incredibly toxic to your health, especially if you're stupid enough to do it in your kitchen's oven.

Pretty much every guide I've seen promoting the "baking idea" (eg. nVidia 8800GT repairs, etc) shows them doing it in their kitchen oven. Why risk the health of your family (and the food cooked in thereafter) by cooking toxic components for something that'll probably not work for long-term anyhow? I appreciate some may use a spare oven for this purpose only, and it's well-ventilated, but for most geeks they'll use mum's oven without her knowing

A heatgun is good enough, and even then it's not that great - the slightest movement while hot will move the component, swimming in solder, making the item impossible to repair again.

JB

 

[MacJunky]

Having a spare oven is good for powder coating metal case parts and stuff as well!