I have a G4 iMac, the original kind with a 15 inch monitor. It forgets the date and time when i unplug it. I suppose that it has a dead battery. Will somebody please tell me how to replace the battery?
PowerMac, Mac OS 9.2.x
Here's a good link:
iMac G4 15" 700 MHz EMC 1873 PRAM Battery Replacement - iFixit
The big issue is reassembly. If you fail to take proper steps to restore the heat dissipation system to its original functional condition, the computer can fry itself.
I like to take apart Macs but I've avoided the G4 iMacs because of the risk of heat damage. Were I in your situation I would stop unplugging the computer and use it as long as you can.
Why are you unplugging the computer? "Green" pundits who tell us to unplug our computers every night to save a tiny bit of energy seldom have any idea of how computers work or the maintenance consequences of constant unplugging. The internal backup battery was never intended to be used every day. It was supposed to keep power to the PRAM to remember setting should the computer need to come off wall power for occasional maintenance or moving
The pundits also fail to realize that many computers are not designed to make that the backup battery user-serviceable. The iMacs before and after the G4 had user-serviceable batteries--Apple made it easy to access the battery. No longer; getting to the battery in a modern Mac is not for the faint-hearted.
https://en.wikipedia.org/wiki/Spudger
"A spudger (or sometimes spludger) is a tool that has a wide flat-head screwdriver-like end that extends as a wedge, used to separate pressure-fit plastic components without causing damage during separation."
Thank you for your reply.
As far as the cooling system is concerned, I don't know. I just put it back together exactly they way that I took it apart. So far, it's working. I don't know how to tell if it's overheating. It's cool to the touch.
I unplug all of my electronic things when I'm not using them to protect them from lightening storms.
You've raised an important point and now I'm worried. I also have a Mac Mini that I unplug when I'm not using it. Am I going to eventually discover that it's impossible for me to replace the battery in the Mac Mini?
Here's an idea, and I'd appreciate having your opinion about it. Suppose that I buy a backup power supply and keep the Mac Mini plugged into it. I can unplug the backup power supply when I'm not using the Mac Mini. Thus, the Mac Mini will always have power but it will still be protected from lightening strikes because of the backup power supply being unplugged. I'm assuming, of course, that it's easy to eventually replace the battery in the backup power supply. Darn, nothing is ever simple.
I'd really appreciate having your opinion about this.
Followup on your Mac Mini model: After posting I went off in search of PRAM battery replacement info on the Mini variants. None appear to be a "slam-dunk." Please post your Mini's sub-model from "About this Mac" ( ex: Mid 2011) so we can do more research into difficultly of replacement.
Apologies if it felt I were "talking down" to you. The fact that you got the G4 back together without it frying means you are technically ahead of most posters here. When I answer questions I have to assume the poster has a very basic knowledge of computers and recommend accordingly until I hear otherwise. You obviously have some skill and experience being inside a computer. That makes all this easier. Good job!
I just now plugged in the G4 iMac and turned it on. It still starts, it's still running, and it remembered the date and time correctly. So, I suppose it's okay for about a year. Historically, I've had to replace PRAM batteries in my old Macs about once every year.
Regarding the Mac Mini, the About This Mac window says "Mac mini (Late 2014)". I went to the Apple Mac Mini page that's mentioned in the tiny manual that came with the computer. There wasn't any mention at all of a battery. So, I'll appreciate any help or advice that you can provide.
As for my level of knowledge, I'm a writer, not a computer technician. I've learned what I needed to learn in order to keep the computers running but I don't know much beyond that. Originally, by training, I'm a Nuclear Engineer (Texas A&M University, 1971), so I have a certain general technical competence. I just don't know a lot about the inner workings of computers. Also I've learned not to get too ambitious. Occasionally, I forget to be careful of my limits. A while back, I took my scooter engine apart and then decided to buy a new engine instead of trying to put the old one back together again.
The 2014 Mini is one I looked up on a takeapart site and it did not mention a PRAM battery for that model either, but did for 2012 models and early The MacTracker database also shows PRAM battery info for the 2012 and earlier models but not for the 2014. Maybe there are using a capacitance device to hold some current.
The good news is that the Intel Macs, other than forgetting date/time, usually don't show many ill effects from a dead PRAM battery. The "Old World ROM" Powermacs (Beige G3 and older), could be real dogs when the PRAM batt died. That madness subsided with the introduciton of Macs with built-in USB.
Aggie engineers rank high on my respect list. You done a G4 iMac--I've not! Kudos to you.
Allan
BS Geology 1969
SMU
"I just now plugged in the G4 iMac and turned it on. It still starts, it's still running, and it remembered the date and time correctly. So, I suppose it's okay for about a year."
A potential problem with the G4 iMacs overheating is related to the presence of sufficient thermal compound on (4) specific spots in the interior. When the base is removed, that thermal bond is disturbed. After it has absorbed heat over a period of time, it doesn't have the same capability to re-bond in those places, by merely coming into physical contact again when the base is reinstalled. There's a thermal pipe in the lower base and the thermal compound is applied at each end. When you had it apart, you probably noticed the white or light-gray pasty or dried residue on two spots in the lower base and on two corresponding contact spots in the upper base. It would be a good idea to remove the base again and following the instructions below. Thermal paste or grease can be purchased from any computer store. It comes in a small, syringe-looking tube or squeeze packets. It's important to apply a small amount and not too much, to prevent excess squeeze-out on the surrounding components. Apple's dire warning on the subject was intended to prevent heat-related failure, inadvertently caused by their authorized repair technicians. Here's the official recommendation:
"Whenever the bottom housing is opened for service, you must do two things:
1. You must clean the original thermal film from all thermal interface mating surfaces (using a plastic stylus or mini-spatula), and reapply thermal paste to the mating surfaces on the thermal pipe.
2. You must tighten the four torx screws on the bottom housing to a minimum of 17 in-lbs. Use a torque driver to ensure that the thermal pipe is firmly mated with the top base. If you do not have a torque driver, you must make sure the screws are tightened by hand FIRMLY, BUT NOT FORCIBLY.
Warning: Failure to follow these steps could cause the computer to overheat and damage internal components."
I was completely unaware of the thermal paste. I didn't notice any residue when I had it apart. I can buy some thermal paste if I can find someplace that sells it. When I take the lower base off again, I can look for the residue. If I can't find any, which is possible since I didn't see any when I previously had it apart, then is there some way that I can determine where to put the stuff? A big red arrow proclaiming "thermal paste here!" or maybe something less obvious that might still tell me where to put it?
After cleaning off the old thermal compound, a new layer is applied at each end of the heat tube, on the (2) surfaces having a hole through which a base mounting screw passes. You can see the locations (circled in yellow) in this photo.
Be sure to clean off the old/residual compound on the (2) corresponding spots in the upper section of the base, against which the ends of the heat tube surfaces come in contact. When ready to reassemble, carefully guide the lower base into position, so the surfaces come into contact evenly. Torque the (4) base mounting screws snugly, to ensure a good transfer of heat via the new compound.
You should be able to find thermal compound at any computer store in your area, that carries components for building or upgrading PCs. You'll have far more left over than you'll apply.
Thank you for the link. I'm studying the procedure, to decide if I'm capable of doing the job. In step 4, what's a spudger?
In addition to machack's response, they can be had off eBay for a few dollars and are super helpful during repairs.
Here's an idea, and I'd appreciate having your opinion about it. Suppose that I buy a backup power supply and keep the Mac Mini plugged into it. I can unplug the backup power supply when I'm not using the Mac Mini.
Might work but I have concerns. Been there, and used up a PRAM battery in less than six months that should have lasted 3-4 years. I turned off the UPS at its front panel; unplugging it would have involved doing the old infantry "under the barbwire" crawl twice a day in office attire. That drained the PRAM batt much too fast. Unplugging may work but check out the cost of a new battery for your backup unit before committing. I had a nice 1000w unit whose replacement batteries were hard to find and as expensive as a new unit. I bought a new unit.
Fortunately mine was a Mac model whose PRAM battery was very easy to change. Not all Minis are. What sub-model is yours?
The easier thing is to check the specs on the UPS. A proper one is supposed to act as a surge protector as well. It should stop over-volt conditions from running up the power cord.
However, that's not the only line. I had a co-worker suffer a fried computer while on an industrial-grade surge protector. The lightning strike reached the computer through an unprotected network cable he forget to check. Our current cable internet provider says their lines are protected at the street level in the junction hardware that parses out signals to the four houses on that node. If you don't have that type of setup then make sure you buy a battery backup that also protects network lines, both ethernet and phone-line systems. They are available, but are usually not the ones that go on sale every other weekend.
Replace the battery in a G4 iMac
