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Apple iMac G5 Power Supply Issues and DIY Apple Repairs

Please help bring my beautiful Apple G5 back to life.

High quality, low ESR, capacitors for sale, or match iMac PSU model type you have to the detailed pictures. Purchase high quality, low ESR, mother board grade, long life, high temperature rated capacitors for your iMac G5 PowerPC mother boards.

Apple Capacitors For Sale - Click Here

Are you having problems with your Apple iMac G5 17 and 20 inch consumer, university, or student models? Does your iMac turn off by itself? Are you seeing strange graphics on the video screen? Is it to the point where it doesn’t even turn on anymore? Is it running hot and the fans sound like a vacuum cleaner?

Well folks, here is one of the problems with many of the Apple power supplies manufactured for their iMac G5, 17 and 20 inch series computers. But fear not, I have put a “How to Fix Series” together on how to fix an iMac G5 power supply and mother board. Power supply information is located right here in this article. I would also suggest reading the latest article on Fat Caps and Ripple Current to have a better understanding of what is happening with Bad Caps inside these Apple iMac G5 power supplies and logic cards.

Also, you can read and see how to fix the G5 mother board over here.

If your Apple iMac G5 power supply doesn’t match up exactly to what you see pictured below, feel free to send me your pictures (inside and outside of the iMac MOBs and PSUs). I also have provided additional pictures for comparing which PSU capacitor kits are available for the various power supplies over at “Inside the Apple iMac“. You can also click the buy now buttons to purchase the power supply kits.

As a side note, if you need to get the data quickly (pictures, files, and programs) off the HD for your old Mac, and place it on your HD on the new Mac, read about the Apple iMac G5 Hard Drive Data Recovery. It is designed for those that want to recover the information from their hard drives on a dead PC or Mac. This HD device works really great for Apple iMac backups too!

Apple iMac G5 Power Supply 17 Inch Model

Apple iMac G5 Power Supply 17 Inch Model
180W – Apple P/N 614-0293

Figure #1

Updated 9/12/09: High Quality Low ESR capacitors, computer motherboard grade, 105ºC, 10mm X 16mm, now available for sale in kit form for the Apple iMac G5 computer MOBs and the PSUs.

The capacitor sizes, included in the MOB kits, are the actual original sizes of the capacitors on the motherboard; making your job much easier to replace them. They are the perfect fit for both diameter and height. Note: The PSU cap kits have been upgraded.

International shipping is available for many countries. If your country isn’t listed for a shipping destination, please let me know to add your country to the list. Please provide your full name (first and last name) when ordering capacitors. Read the Shipping for shipping and delivery information.

If you are interested in more than 10 MOB cap kits, please send me an email with a total amount of how many iMac G5 cap kits you are looking for, along with a note of which of the two different cap kit sets you are interested in. Note: Apple early model and late model iMac G5s with the PowerPC processor have different quantities of caps required on the MOB. Click the eCommerce link. Capacitor information is provided there. Verify what capacitors your Apple iMac needs, and bring your iMac G5 back to life today.

Send me an email with your questions, or special order requests. I now have all the power supply cap kits available. Feel free to contact me any time, with any questions. Take a look at the PSU cap kits that are available for purchase.

Just a brief update for those that have been out of the capacitor loop. About the time Apple was building their G5 line of personal computers, several Taiwanese electrolyte manufacturers began using a stolen electrolyte formula that was incomplete, and lacked key ingredients needed to produce a stable capacitor. The missing ingredients caused the electrolyte in the capacitors to break down, evaporate, leak out of the cap casings, caused overheating of the capacitors themselves under normal load conditions, and subsequently caused exploding poppers. Consequently the capacitors started bulging, overheating, and exploding in many of the power supplies and mother boards manufactured by Apple, Dell, Hewlett-Packard, and others which has been documented by numerous articles online. In fact, Dell took a “$300 million financial charge on its earnings to cover costs associated with the replacement of motherboards with faulty capacitors in some of its Optiplex workstations” in late 2005 early 2006. For those of you that are interested, I have documented a do-it-yourself repair procedure and an educational information manual on the Apple iMac G5 motherboards along with students’ user comments.

Note: Apple provided an iMac G5 Repair Extension Program for Video and Power Issues: See the frequently asked questions section at Apple about which models and serial numbers are/were covered. Howeve
r, in all likelihood (“As of December 15, 2008, this program is now closed.”), the iMac G5 Repair Extension Program has run out its course for most, if not all iMac G5 PowerPC owners. See Apple information on the power supply and the video and power issues documents. You can read the actual repair extension program text in the Apple iMac Mother Board article, exactly as it was in the original Apple documents. The program was available for certain iMac G5 PowerPC models that were sold between approximately September 2004 and June 2005 featuring 17-inch and 20-inch displays with 1.6GHz and 1.8GHz G5 processors. You may also go to any Apple Retail Store with a Genus Bar and have the Apple folks take a look at your iMac for you. Find the nearest Apple Retail Store – Genius Bar in your area, and even make an Genius Bar appointment online too. Apple provides technical support for your Mac, iPod, Apple TV, and iPhone at the Genius Bar too.

Identifying the Apple iMac Power Supply Problem or iMac G5 Motherboard Problem

Apple provides a diagnostic guide for determining whether the problem is with the motherboard or the power supply. See the following link to the: iMac G5: Troubleshooting when your computer won’t turn on. Included in that Apple document are instructions of how to turn on an iMac with the back cover off. There are two small buttons located under the fan cover as displayed in the document. One button is the internal power button, and the other button is for resetting the System Management Unit (SMU) which is located right next to the internal power button. “Note: If you’re using an iMac G5 (Ambient Light Sensor) computer, your SMU was already reset when you unplugged and replugged the computer. You won’t see an SMU reset button to press, and that’s OK, as this action has already been done. (If you aren’t sure which iMac G5 model you have, click here for help.)” Source: Apple

Since, I feel that I have been somewhat of an online trailblazer on documenting the iMac issues and the Apple iMac G5 motherboard repairs project, I thought I would take the time to dive into another area that many of our readers have stated is also a big problem with the Apple G5 line of computers. That big issue has to do with the main power supply installed in the iMacs are dying and dropping like flies. From what I understand (though not confirmed) about the iMac PSUs, is there are at least several different power supplies used by Apple in their iMac G5 model lines. The part numbers are located on the back of the PSU case. This power supply is Apple P/N 614-0293 Rev. A 180W. The serial number has a barcode graph. The various models associated with this particular DIY repair document are for Apple: iMac G5 (20-Inch), iMac G5 (20-Inch iSight), iMac G5 (17-Inch), iMac G5 (17-Inch iSight), iMac G5 ALS (17-Inch), and iMac G5 ALS (20-Inch) consumer, university, and student models. See the Apple Power Supply, 17-inch Replacement Instructions for how to remove and install your power supply unit. If you have an Apple model with the ambient light sensor, pay particular attention to not breaking the wiring or the sensor that is mounted to the lower portion of the power supply when removing the PSU. Ok, that gets your power supply unit out. Now what?

There are several service repair or replacement options available for your iMac G5 power supply.

  1. Order a new power supply from Apple Parts & Services.
  2. Order a new PSU, rebuilt power supply, or have your PSU repaired from an outside source.
  3. Repair the power supply unit yourself.

Before I talk about option number three, I would like to point out that when you buy a used or new power supply from Apple or another vendor, you have no idea whether the capacitors that are used in this new or used PS are any better than the ones that were installed in your particular iMac. In all likelihood, the new or rebuilt PSU might not last either. I have heard stories of Apple Service replacing a person’s iMac power supply, and several months later having to do it again. With that being said, it seems obvious that you are taking a chance no matter what you do. By-the-way, the cost of a power supply for an iMac will likely set you back 150 to 200 buckaroos. To me, $150.00 or $200.00 seems like an awful lot of money to shell out for such a small power supply that might not last more than a few months. Capacitors actually get old just sitting on the shelf.


Apple iMac G5 17 Inch Model

Apple iMac G5 17 Inch
Figure #2

With many of my readers sharing their iMac G5 stories, both in the online comments section and sending emails to me documenting their problems they are having with their Apple iMacs, I thought it was prudent to take the next step and see if I could discover first hand what was going on in the field with these 17 inch iMacs. I already own an Apple iMac 20 inch model but I needed a 17 inch one for further investigative work. So, I went searching for a broken iMac G5 computer that I could get my hands on for a fair price. I didn’t want to spend a ton of money on a broken Apple to do my research, but I needed to do some more engineering and technical failure analysis of the problems of iMacs not turning on because of mother board problems or a power supply situation. Many people kept telling me that they had an iMac G5 17 inch model computer with no physical signs of bad capacitors on the motherboard. I wanted to verify this for myself. I found an iMac G5 17 inch on Craigslist from a guy that felt he got ripped off by someone selling a supposedly good working iMac to him a short time back and then when he plugged it in, it didn’t work. He took it to the local Apple Genius Bar folks and they said he needed a new motherboard. So, after talking with the seller and asking him some questions about this particular iMac, we settled on a fair price, I met him in San Ramon, CA, and purchased it from him. In my opinion he was a straight shooter, and was nice enough to allow me to open the back cover up before I purchased it in order to make sure all the hardware was inside, i.e., hard drive, motherboard, power supply, fans, memory, cd/dvd SuperDrive. However, he had given away the keyboard, mouse, and the software to some friends. Oh well, keyboards and mice are not very expensive, and if I need Mac OS X software, I can purchase that too.

So, I get my new, broken, what an oxymoron, iMac G5 back to the office and I plug it in, push the power button, and it just sits there staring at me with a blank screen. Nothing powers up. Dead in the water. Dead on arrival. DOA, just what I wanted. Really! Yes, it was time to go to start my engineering class work. I opened the back of the computer once again and took a much closer inspection of the motherboard and the capacitors. Believe it or not, all the capacitors look good on the MOB, just like some of my readers have documented with their own stories in written emails I received from them. This is a completely different issue than what I saw on my iMac G5 20 inch motherboard problem with the bad capacitors on the MOB, with some caps just about ready to pop. All the capacitors on this motherboard looked completely intact, with no signs of swelling, bulging, or electrolytic juice leaking out anywhere to be seen on this 17 inch model.

The next step in my troubleshooting analysis probe was to remove the power supply and do the smell test. Yes, use your other senses other than eyesight when troubleshooting electronics or checking out other industrial equipment. The smell of burnt electronic components can sometimes be detected months and years later, even after a burnt component has been replaced. I placed the power supply up to my nose, and I thought I got a slight whiff of that unforgettable smell of burnt electronic components. Now, it was time for the 20/20 vision eyesight test.

Danger High Voltage Electrical Shock Warning!

This information is provided as a safety precaution and to be careful. A warning at this next stage of the technical analysis is warranted. Electronics, and power supplies in general have high power electronic circuits which can cause a body harm if you touch the wrong thing, even if unplugged. First off, make sure your power supply is not plugged into the AC power outlet. Note also that power supplies typically have a primary high voltage input side and a secondary low voltage(s) output side. The high voltage input side can have large filtering capacitors which can store an electrical charge (DC voltage potential) for a long time, even after a power supply is unplugged from the AC power outlet. Take the precautionary step, and discharge these primary capacitors (after it is unplugged from the AC power) with a screwdriver or place jumper wires across the leads prior to working on the PSU printed circuit board. If you have a different type of supply than what is shown here, with large cylinder capacitors standing up on the primary side, you will not be able to get to the leads on the bottom of the circuit board in order to discharge them. However, if a power supply is left off, unplugged for a period of time; certainly if it has been off and unplugged for an hour or two, the majority of the charge will have dissipated from the capacitors due to in circuit resistance and time.

The iMac G5 PSU case design, is one by which Apple’s engineers designed their power supply units with security torx fasteners (screws) attaching the metal cover housing to prevent unauthorized disassembly, and also I am sure to prevent anyone from getting hurt. I do not own one of these security torx drivers, as I suspect most people can say they don’t have one in their tool box either. I was having an email conversation over the past week with a physics professor at a university. He mentioned he has ten 1.6GHz 17″ G5 iMacs at the university, four of which have already collapsed completely. He was also the first to mention to me, about the security torx key being required to open the PS cases.

In this case no problem on the mother board, but big trouble in the power supply (lots of caps in trouble, one totally blown). One can see some of them through the power supply case, so you might want to take a look at yours.

Be careful of the two high capacity capacitors in the unit, they can be lethal. Ph.D., ARCS

I was able to unscrew the torx screws using a precision miniature screwdriver, and broke out the small internal security tabs within the head of the torx screws themselves. Once I did that, the torx screws were relatively easy to remove.

Pictured Below Are The Electronic Components and Printed Circuit Board Completely Removed From The Power Supply Unit

Apple iMac G5 PSU Capacitors Locations

Capacitors’ Locations, Sizes, and Electrical Values For Apple iMac G5 Power Supply Unit Diagram Schematic.
Click image for close up view of G5 PSU capacitors.
Figure #3

Here’s a confirmed list of the secondary (low voltage) side PSU capacitors installed in the iMac G5 17 inch model. It maybe different on the iMac G5 20 inch, ALS, and iSight models. Please send me an email confirmation or comment on the iSight models, iMac G5 20 inch models, and ALS (Automatic Light Sensor) models, along with any capacitor sizes, quantities, and values would be much appreciated. Please include the Apple p/n and the last four digits of the Apple EEE Code (The last four digits on the serial number). See Cap Note:

  • 3x- 1000uf 6.3V 8mm x 16mm
  • 2x- 2200uf 10V 10mm x 24mm
  • 1x- 1200uf 16V 10mm x 24mm
  • 1x- 4700uf 6.3V 10mm x 30mm
  • 1x- 1000uf 35V 12.5mm x 20mm
  • 1x- 330uf 35V 10mm x 20mm

What you are looking at in figure #3, once you remove the cover of the PSU, are signs of bad capacitors all over the printed circuit board. The first image (Figure #1) above shows the blown capacitor, burnt on the top, and burnt residue on the cover too. If you look closely at Figure #3 and Figure #4, you can see telltale signs of capacitors that are bulging and getting ready to blow their tops. Note the gray silicon rubber adhesive that has been squeezed into and between the electronic components on the circuit board. Some believe that this goop was used for anti-vibration and noise dampening as can be seen with the application of a small amount of goop on a potentiometer adjustment located in the top middle of the PCB, next to the transformers. I can understand the use of it to hold the large primary capacitors in place. However, in my opinion, I believe this was an attempt by the manufacturer (Apple) to make it more difficult to repair the PSUs when using it so liberally throughout the entire PSU. If however, I am wrong, and this is not the case, and the designer intended this goop to be used for anti-vibration noise dampening purposes, the assemblers seem to have gone overboard on their use of it, and it has had an unintended consequence of heat build up. If you look closely at the tall boy cap, I think this one ended up sandwiched in an oven, right next to the coil choke (see closeup picture on Figure #4). In my opinion, it’s not like the small capacitors are going to move once they are soldered in place. It’s also likely that this silicon rubber filler was instrumental in the early failure of the other capacitors too. Excessive heat buildup likely resulted from the insulating characteristics of silicon rubber encapsulation which would result in a runaway thermal chain reaction and cooked the components. Cool air circulation was none existent in these encapsulated areas of the PSU. This silicon adhesive must be gingerly picked at and cut away, in order to get proper access to all the bad capacitors, and be able to remove them when they are unsoldered from the PCB.

Directly below in Figure #4 is a slightly angled picture view, with a closeup of the capacitors on the iMac G5 Power Supply printed circuit board in view and most of the silicon rubber goop removed.

Closeup View iMac G5 Power Supply Printed Circuit Board

Closeup View of Apple iMac G5 Power Supply Printed Circuit Board With Bad Capacitors
Click image for an even closer view of the PCB and PSU capacitors.
Figure #4

The tools I used on the PCB for cutting and picking away at the silicon adhesive are on display in Figure #4 too. I used by trusty precision miniature screwdriver (Husky model HD-74501 S “a gift”) with multiple bits in the handle, which came in handy for removing the torx fasteners and picking away at the small sections of silicon adhesive, the small retractable utility knife box cutter was used to cut away the big gobs of silicon rubber, and the inch/metric 6 inch scale was used for measuring the capacitor physical sizes.

So, the bottom line is most of the secondary low voltage side capacitors must be replaced on this particular G5 PSU. I will probably replace them all. Some of the capacitors I am told are difficult to find. This is especially true of some of the smaller diameter capacitors. Spaces are limited on the PCB. Also, note the one 350 microfarad 35 volt 10mm x 20mm capacitor (Figure #4 with close up view) that is located under the copper heat sink in the middle of the PCB. This is going to be most certainly problematic for capacitor replacement, since it is most likely that I will have to remove the 1000 microfarad cap in front of this 350uf capacitor in order to slide it out from underneath the heat sink assembly. The heat sink assembly is mounted to what appears to be voltage regulators that are impossible to remove without first removing other inductor choke coils, capacitors, and other components in front of the heat sink assembly.

Surface Mount Technology SMT SMC SMD
Surface Mount Technology – SMT
Surface Mount Components – SMC
Surface Mount Devices – SMD
Figure #5

A word of caution about the bottom surface of the PCB before you proceed with on-board capacitor replacements. Be careful not to damage any of the SMC, Surface Mount Components (Figure #5 pictured on the right) located on the bottom of the printed circuit board. These discrete SMT, Surface Mount Technology micro components are very small (some of the SMD, Surface Mount Devices, are hard to see with the naked eye) and consist of SMC diodes, SMC resistors, SMC capacitors, SMC transistors, and SMC IC chips in close proximity to where the large electrolytic capacitor leads protrude through the bottom and are soldered to the plated through holes of the PCB. Be extremely careful when soldering next to these SMDs. If you heat up a SMD by accident with the soldering iron, (see lead-free soldering tips for more soldering information) you will potentially dislodge it from its PCB pad. Figure #3 shows the PCB top side surface before picture, with all the silicon rubber adhesive stuck between the electronic components. Figure #4 picture is after the silicon rubber, for the most part, has been removed from the components on the secondary side of the PSU.

Now, the next step in the process is to purchase the nine electrolytic, radial leads, low ESR capacitors designed for tight spaces. For most folks out there in Internet land, I realize there probably is much technical information to digest here in one quick reading. I feel like I have written and photographed a technical documentary. I will most likely publish an updated technical article or add to this document when I locate new capacitors and proceed with the the installation of these new low ESR electrolytic capacitors. Cap Note: I suspect I will have some different suggested sizes to use for cap substitutes. You are free to print out this document using the “print button” for your personal use, but you are not granted permission to distribute or publish it anywhere else without my prior approval. That goes ditto for all the articles published on this website too.

All information provided here is for instructional purposes only. Please note that I cannot be held responsible for any damage that you might do to your computer or yourself. This website is for educational purposes only and you are responsible for everything you do with the given information. You are responsible for the health and welfare of your own body and computer.

I hope this iMac repair training course series of articles helps everyone that is facing a decision of possibly having to go to the precious and non-ferrous metal reclamation and computer electronics recycle center with their crippled or broken down Apple iMac now and in the future. After all, I believe that these Apple G5 iMacs are not an EWaste product, and are most precious and beautiful machines for their owners to use. I think there is a lot of life left in these very powerful iMac G5 computer machines for today and tomorrow. At least I have a documented road map and general circuit diagram schematic of the main power supply components, along with engineering failure analysis that I will be using myself for technical reference for now and in the future. By-the-way, I now have a large quantity of high quality, low ESR, electrolytic capacitors available for sale for the DIY Apple iMac G5 motherboard repairs. See motherboard repair posting for quantities required. Or, you can order directly from my online store at Out West Sales today.

Power Supply iMac 20 Inch Model Apple Part Number — Apple p/n: 614-0326

Capacitor List and Diameter Sizes For Power Supply Apple iMac 20 Inch

Click this iMac 20” PSU Super Close-up View or Picture Above for Close-up View
  • 330uf    35v    10mm
  • 1200uf   16v    10mm
  • 3300uf   10v    10mm
  • 2200uf   10v    10mm
  • 1000uf   25v    10mm
  • 1000uf   10v    8mm
  • 120uf    50v    8mm

This particular power supply is (Apple p/n: 614-0326)

Note: According to Alex, capacitors would not exceed 32mm length. But also note that the cable wiring comes over the top of some of those capacitors on the right front section of the PSU. If the capacitors are too high, the wiring will not clear the PSU cover.

“Jim – do you have a pic of a 20″ iMac G5 power supply guts? Mine had the bulging/leaking capacitors. I removed them but need 2 reinstall and lost my notes as to which went where. On the top right hand side area is where they go.

I need to know where each size goes back. They are as follows: 1200mF 16V, 3300mF 10V, 2200mF 10V and 1000mF 10V any help is greatly appreciated.”

Sorry, I haven’t taken the 20 inch power supply apart, so I don’t have any pictures. I’d appreciate it if someone else can send pictures to me of the 20 inch model and I’ll post them here. Click my email address “James” on the right side to send images. Special thanks to Alex B. for his Power Supply iMac 20” picture above.

Additionally, if anyone finds a source available for engineering prints, technical drawings, or electronic schematics for Apple iMacs, please send me an email notice or send attachments to James. James is my clickable email address located on the right side of the website, just above “Chat with Jim Warholic” when I’m available online. I and others would really appreciate the circuit board schematics if you have them. Thank you, Jim Warholic

There is another option worth exploring for the Apple iMac G5 Power Supply. The option is to possibly convert a standard PC ATX power supply and use it for the Apple iMac. Wiring changes on the P1 pin-outs have to be made first. See the following note and image.

Accelerate Your Macintosh! News Page

iMac G5 Power Supply Connector Pin-Out (Voltages)
“I haven’t been able to find this anywhere using Google, so I took apart my iMac G5 (17-inch rev A) power supply and made a pin-out diagram.
-Chris N.”

Do not attempt the following if you do not know what you are doing. Severe damage could result. See note above concerning the information provided here. Compare the Apple iMac Pinouts diagram with that of the ATX Power Supply Pinouts Diagram. Pin modifications need to take place before plugging it in. Note also, there is a 24 Volts output on the Apple iMac Pinout diagram that is missing on the ATX Power Supply Pinout diagram. However, based on a thread in an online Apple Forum at InsanelyMac, titled iMac G5 Power Supply Question, a person as recently as January 2008 modified an ATX power supply and didn’t use the 24V, but I think he used an external monitor, and the iMac worked with this setup. Some folks indicate that the +24V is used for the internal backlit display. See quotes: “+24V is used to power the LCD inverter” and “24VDC line looks to be for the display (backlighting)”. Read full quotes in context at InsanelyMac Forum.

With that iMac G5 mod in mind, maybe someone can come up with an external power supply box, and just plug it in to the iMac P1 plug on the motherboard. Another person also emailed me in October of 2008 and mentioned he had this ATX power supply working for an Apple iMac g5 too.

This was recently posted as a comment by another person for the pin outs and voltage information: Note, I have confirmed this pin out information. Update: The various pinouts have been confirmed by at least one other customer also. Click the how-to link for more details about how to measure the iMac G5 power supply voltages and turn on the PSU when the PSU is removed from the iMac computer.

My 20″ iMac Power Supply connector – P-1

1. +3.3 – BlackA3B 12. +3.3 – BlackA3B
2. +3.3 – BlackA3B 13. +12v – BrownA3B
3. GND – BlackB4B 14. GND – BlackC4B
4. +5v Gray/PurpleA4B 15. On/Off – Gray
5. GND – BlackB4B 16. GND – BlackC4B
6. +5v Gray/PurpleA4B 17. GND – BlackC4B
7. GND – BlackB4B 18. GND – BlackC4B
8. PG – Blue 19. +12v – BrownA3B
9. +5.1Vsb – Purple 20. +5v Gray/PurpleA4B
10. +12v – BrownA3B 21. +5v Gray/PurpleA4B
11. GND 22. +20v – Brown

FYI: More information for measuring the voltages can be found at my how to measure iMac G5 power supplies article. Be sure to read the article comments section for additional details.

Pin 22 supplies Panel voltage. Using a modified ATX Power supply (Need 12+ on pins 12 and 18), and the good 20 volts on the dead Apple Power Supply and a ground, I was able to boot my 20″ iMac using the combination of both power supplies. Someone else posted the pin out elsewhere on the web. I replaced just the domed capacitors on my power supply and still no luck. Can some of the capacitors be bad and not be domed? Can you check capacitors on the board without removal? Some go to infinite and stay, other go to infinite and fall back to zero when using an ohm meter?

A few points to consider when checking capacitors in the circuit and on the circuit board. It doesn’t always give the correct reading with a ohm meter whether using digital or analog  meters because of other components affecting the readings of what you might be trying to check in the circuit. Yes, capacitors can be bad without physically looking bad. The electrolytic juice can dry up on the inside. And one more point that I would like to make, it sure would be nice to have a circuit board schematic for the power supplies in my hands. Feel free to send me one if you have it. Thanks.

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3/18/2009 Update: Installed new power supply in this iMac 17 inch G5 computer. Success! Installed keyboard and mouse too. Now I need new software for the white house.

A important note here is that I recommend only using “new” low ESR, long life, computer motherboard grade and switching power supply grade capacitors for all repairs. Do not use unknown surplus caps, or even new or surplus caps that have been sitting on the shelf for ages. My power supply was too far gone. It had something else blown in it.

I have the extra long life capacitors (rated at 10,000 hrs. on the large uf rated capacitors) and all are low ESR ratings for the power supplies, in stock now. Please take a look and compare these Apple iMac power supplies to your power supply before purchasing.

Click Here to Buy Capacitors, or click here to match up your iMac PSU variation to the detailed pictures. Purchase high quality, low ESR, mother board grade, long life, high temperature rated capacitors for your iMac G5 PowerPC mother boards.

If your iMac power supply doesn’t look exactly as above, or would like to have a free consultation, and provide a visual evaluation for me to take a look at please send in your Apple iMac G5 pictures, to compare.

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  • Jim Warholic says:

    The Arctic Silver heatsink thermal compound is for the logic card mother board. Take a close look at the pictures in my posting with the details about replacing the bad caps on the iMac G5 MOB and there is a picture part way down showing the logic board bottom side view of the main board with a small exposed square area. This small square chip makes contact with a large flat heatsink, that when mated together with a very thin layer of heatsink compound, dissipates the heat from the main chip to the heatsink. If you do not replace the heatsink compound, you run the risk of damaging the main processor chip.

    Also, pay particular close attention to the details of not applying too much of this thermal heatsink compound to the board. Even though the compound is not electrically conductive, it is capacitive in nature and and can adversely affect the operation of the computer. “If it is sitting on the components, or even above the insulating copper tracings of the circuit board, it has low impedance at the clock frequency — it is a virtual short circuit.” See the full warning about the processor chip not working because of someone getting the thermal compound on other components and areas on the bottom of the pcb.

    Yes, the soldering can be a bit of a problem (a bit more tricky on the logic card) if you do not have a hot enough soldering iron. The power supply circuit board is actually easier to unsolder the bad caps as compared to the logic card. I suggest folks read over the soldering article I wrote concerning lead-free soldering and soldering tips.

    Hope that helps clear it up a bit.

    March 16, 2010 at 11:33 PM
  • Rich says:

    Hello Jim,

    First off thanks for your site and service.

    Sunday morning 3-14-10, iMac G5 starts up but kind of a delay.
    Sunday afternoon 3-14-10, iMac G5 not longer powers up.
    Sunday evening 3-14-10 web search turns up your site.
    Monday morning 3-15-10, power supply inspection shows 6 bloated caps.
    Monday afternoon 3-15-10, power supply “B” style cap set ordered.
    Monday evening 3-15-10, email informing me order sent out.
    Wednesday afternoon 3-17-10, cap set received.
    Wednesday evening 3-17-10, caps replaced iMac G5 now works again. And starting up faster and running quieter than before.

    March 18, 2010 at 8:35 AM
  • Anonymous says:

    Hi Jim,

    I was curious on whether or not you replaced the caps on the logic board of this 17″ model you were working on in the article. I have a 17″ model that seems to fall in the same category as the unit you worked on. It has exploded PSU caps but the caps on the logic board look fine. I’m wondering if replacing the PSU will be enough to solve my issues or if I will be required to replace the caps on the logic board after replacing the PSU.


    March 22, 2010 at 4:52 AM
  • Jim Warholic says:

    In this particular case, for this 17 inch iMac model I talk about here in this power supply repair article, I only had to deal with the power supply as the problem. As I have found, and heard from other folks too, sometimes it is either the MOB or the PSU, and other times it is both. The 17 inch iMac G5 is still functional, though I think I have too many computers around the house, at least my wife thinks so.

    March 22, 2010 at 9:46 AM
  • Mr C says:


    update, Replaced all caps on MOB and power supply worked for a bit. until complete shutdown. rechecked PS and found one cold solder joint. re-soldered and still no voltages. ordered re-furb PS on ebay for $112 and has been running for 1 hr. Can a defective MOB cause PS failures? Keeping my finger crossed.

    April 7, 2010 at 4:07 PM
  • Mr C says:


    There are three fans in the Imac G5 20″ 2005 rev b. Upper fan on left, hard drive fan (upper right) and lower fan on bottom right. I feel discharging air out the bottom vent. what is the air flow direction, intake from the back and vent out the bottom? also what is an excessive temp reading for CPU and HD, i’m getting about 60C for CPU and 50C for HD. Also is there a program that test fan operation. just want to confirm these reading/observations are correct.

    Thanks again.


    April 7, 2010 at 4:23 PM
  • Jim Warholic says:

    As far as I have seen, the fans blow the air out of the top back of the iMac. If you are feeling hot air coming out of the bottom, I suspect there may be internal air flow restrictions that is preventing the hot air from exiting out of the top. Check all your vents and the cooling fins of the heatsink assembly to verify that they are completely free and clear of debris.

    Also note that there are brand new PSUs available from other sources for about the same price as you mentioned from eBay.

    I think there may be some fan control software programs available to set the minimum fan speeds. I am not sure if there are any programs that really verify the actual fan speeds. Try a Google Search for: iMac fan speed software. Note that I have not tried any of these softwares myself.

    April 8, 2010 at 12:12 AM
  • Bill says:

    Thanks Jim for great website. Even though I just bought a new power supply and installed it. Your site has so much information on it I felt sure this would be the cure and it was. This G5 will be a nice back up to newer computers we have recently purchased. Your site saved me from just recycling the computer.

    Much appreciated

    April 17, 2010 at 11:00 AM
  • Marc Collin says:


    I have a new story with a Imac G5 17 and some remarks may be interesting. I found this iMac not working at all in a recuperation center. I did the power supply test and all voltages seemed OK. The motherboard looked in good condition, no sign of bad capacitor. Having a standard ATX PSU I decided to try the little mod to make it compatible, and to my surprise, the mac booted. I have seen that some people beleived the 24V was for the backlite, but the backlite was working OK without it; meanwhile the Firewire was not working — so the 24V seems to be intended for firewire. To brign Firewire on, I did use pins 11/22 of the iMac powersupply (so I was using 2 PSU) and it worked. I am now testing to see if the motherboard will present bad symptoms within some hours of usage.

    So I can confirm 1) the mod suggested to use an ATX psu with the iMac on the page is working fine; at least, it is a way to insure that the problem of a iMac belongs to the PSU and not to the motherboard; 2) that the 24V on the iMac is used for Firewire and not for the backlite, and 3) that the instruction on Apple page, and also a voltage test of the PSU can make one thinking the motherboard is dead when in fact the problem is only within the PSU.

    Thank you very much for your site and the very complete information on it. The iMac I found will not be salvaged as the lcd is also cracked (I suppose the owner was unhappy when an Apple technician told him the machine was dead and threw it away…) but at least the board is good and will serve to salvage another one.

    May 25, 2010 at 8:22 PM
  • Will says:

    Jim, first thanks for all the great work you have done on putting this site together. So I purchased a non-working imac last week and started examining it. Realized the power supply was blown and replaced some bulging caps as well as shorted the fuse that had blown out to see if it would start up. The power supply now allows the first led on the logic board to light up. However I think one of the SMT transistors on the back of power supply is blown, the one next to R4. Tried looking for it online but no luck so far. I am sure I can replace it just need to find the part, any idea what kind of transistor this is? I have the iMac “C” model PSU.

    May 25, 2010 at 9:19 PM
  • Will says:

    Jim, I was able to fix my power supply by replacing the transistor next to R4 on my “C” model PSU. The transisor is labeled as 1P and turns out to be a NPN FMMT2222A silicon Planar switch transistor. Since I am a bit impatient, I surveyed some old intel motherboards I had with a magnifying and glass to see if there were any on those boards. Found several on one board so went about desoldering one and resoldering on the iMac psu. After the initial install the PSU was still only powering the 1st logic board Led. Found after some investigation that one of the transistor pins was not making contact with the pad. After adding more solder to the joint I tested it using a normal ATX power supply tester and most of the lights went green. I then plugged the PSU into the logic board and the iMac chimed and showed the hard drive missing icon. (This is good since there is no drive installed right now.) I am pretty excited and look forward to completing the entire iMac repair.

    May 26, 2010 at 9:24 AM
  • ron segal says:

    Looking for some information about the DC pinouts of a 661-3780 power supply for a G5 20″ isight. This is a 185w supply with 5 output pins only. Have been trying to track down detaisl but no luck so far. The supply is dead and badly burnt on one spot on the circuit board (does’t look repairable). Wanting to use an ATX supply to check that the machine is otherwise ok, before buying a new power supply unit, particularly with shipping costs on top to New Zealand. Any help would be appreciated.
    Very best regards from down under – Ron

    May 30, 2010 at 7:37 PM
  • Jim Warholic says:

    Hi Ron,

    Sorry, the only thing I have for pinouts is located here:

    iMac Power Supply Pinouts and Voltage Measurements.

    I know that is probably not going to help you much, but maybe someone else has more information that they could post for that particular power supply and iMac model.

    May 30, 2010 at 8:10 PM
  • Ron says:

    Thanks for getting back so quickly Jim. Typical, I just found the answer:

    For an imac G5 17″/20″ isight (early 2006)
    Mine is an EEE code UQP
    with 661-3780 power supply with only 5 pinouts
    these are:

    Grey: +12V
    Grey: +12V
    Black: ground
    Black: ground
    Brown: PFW (battery powered signal between +3 and +6.5 volt to switch power supply on)

    Hopefully this will also help somebody else.



    May 31, 2010 at 8:05 AM
  • Larry says:

    Hi Jim,

    What a great website! I’ve already repaired 1 Mac with all your details, and I’m hoping for a little help on my second Mac.

    I’m rebuilding the type ‘B’ power supply. As I was picking all the goop off a blown cap, I smacked the ZD4 next to it and cracked it. I’ve found on the web it’s a Zener Diode but nothing else.

    It’s located between cap C45 and the two black wires. I couldn’t see any numbers on it and it crumbled when I removed it from the board.

    Any idea on the details of it?



    June 17, 2010 at 3:26 PM
  • Jim Warholic says:

    To Larry,

    I’m not sure what value the component that you are referring to is.

    Hello Folks,

    Just an update message for some folks doing both the motherboard and power supply units.

    It is important to replace the entire bank of capacitors of both types on the motherboard especially when seeing just a few bad caps on the motherboard in the first place. Refer to my Apple iMac G5 motherboard repairs article for more detailed information about Apple motherboard repairs. Do not take a shortcut here.

    You can also dive into the power supply and check the voltages. Even if the power supply is good or bad, and if you only replace the visually bad caps on the motherboard, there is a good chance you can blow out the existing power supply or even a new power supply. This bears repeating again, even if the other caps on the motherboard look good, it is highly likely that there are additional bad caps besides the bad caps that are visually bad. This also holds true for bad power supply caps.

    Take the time to do it right the first time and it is highly likely you will not have to take the time to do it right the second time.



    June 22, 2010 at 9:25 PM
  • Robin says:

    I recently ordered the cap kits from you and replaced some caps in my G5 17 but I’m still having issues.

    Upon initial inspection, LED 1 was flickering rapidly (and 2-4 were unlit) and the five 1000uf 16v caps on the logic board were bulging, so I started with those 5. No change with LED 1, so moved on to the power supply. I opened it up and sure enough, 4 bad caps so I replaced all 9 caps to be safe. I’ve checked the voltages on all the pins and all are correct and stable. However, when I plug the power supply into the logic board, LED 1 (and all the others) don’t light up at all.

    Any thoughts as to why the logic board won’t light LED 1 even when the voltages seem ok? I’ll replace the remaining caps on the logic board, but I want to make sure my power supply is operating correctly to prevent damage of the new caps.

    Thanks for all the hard work.

    June 26, 2010 at 2:50 AM
  • Jim Warholic says:

    Hi Robin,

    With LED #1 flickering to begin with, that was certainly a sign of a PSU problem.

    The fact the LED #1 won’t now come on is a sign that the PSU still has a problem. However, with the fact that bad caps were found on the MOB, it is always highly advisable to replace both the 1800uf and the 1000uf capacitors in their entirety.

    Note that the PSU could have something else blown out in it besides the caps, even though the voltage might be present under no load conditions.

    Some other things to double check:

    * Make sure all the plugs are installed on the MOB.
    * If LED #1 is not lite, when plugged in, it still is likely that something is wrong with the PSU. LED #1 is showing that trickle voltage is reaching the MOB.



    July 5, 2010 at 8:32 PM
  • Superdave says:


    Thanks so much for your site!

    I’m repairing my non ALS, non iSight 17-in G5 PSU, and am looking for the correct kit to purchase. how am i to tell what type of PSU I have?


    July 22, 2010 at 2:15 PM
  • Jim Warholic says:

    The best way to verify which kit is required, is simply open it up and compare to the pictures I have posted here. If you do not see the exact replacement, it is still possible that one of the kits will work for you, if the capacitor values match up to your needs.

    If you are unsure, I suggest taking a picture and sending me an email, using the email link on the right side of the site. You would have to click on the link to send an email. I have it undisplayed so the S Bots do not find it. Look for Email: James to send it to me.

    July 22, 2010 at 2:31 PM
  • Kevin Babcock says:

    Hi Jim,

    Looking for your opinion. I have a Early model G5 iMac back that I rebuilt the power supply for about 7 months ago. The system starts booting goes about a minute or two then power shuts down. All looks fine until it shuts down. My 1st thought was power supply but I did just rebuild it. One capacitor on the mother board is bulging, a 6.3 volt 1800 uf located close to the power supply and its plug into the MB. I checked out the LED lights to check the power supply and all seem fine until the system shuts down. What are your thoughts.


    August 15, 2010 at 12:41 PM
  • Jim Warholic says:

    If any of the motherboard caps are showing signs of bulging, the other caps are certainly bad or weak, and on their way out too. Always suggest changing all the 1000uF and 1800uF caps at the same time when any of these are showing signs of bulging. If you don’t change them all, you will surely be back in again in the near future. Also, the other weak capacitors will start taking out good capacitors, if they are not replaced as a group.

    August 25, 2010 at 9:50 AM
  • rt says:

    Hi Jim,

    Just wanted to add my name to the list of iMac G5s returned from the dead (well dying really).
    It was lasting around 5-6 hours max even at idle, before switching off due to the psu overheating.
    Bought a psu kit from you quite a few months back, but not had time till this weekend to get around to replacing the caps.

    Replaced them yesterday and have been up and running for around 20 hours now. Been stress testing the machine at 100% cpu and also generally using it – video, music, internet.

    Had forgotten how hot the iMac G5 design lets the disk get -saw 60 degrees C earlier! So apart from frying the disk as it always did, it’s all good.

    Thanks for the site and a rejuvenated iMac!

    October 3, 2010 at 10:30 AM
  • Chris says:

    If LED1 is not on check the fuse on the PSU if you have replaced the caps.

    October 5, 2010 at 5:17 PM
  • Jim Warholic says:

    Thanks Chris for that tip. I should also point out, that sometimes the fuse on the PSU is hard to spot. It is located on top of the PSU circuit board, and generally underneath where the main AC plug plugs in. These are soldered in, inline fuses. Sometimes the fuse is covered by a black heat shrink tubing.

    October 5, 2010 at 6:35 PM
  • Chris says:

    Thanks you Jim for having this info out there. I have repaired a dozen of MOBs and PSUs thanks to you.

    October 7, 2010 at 6:56 AM
  • Kristofer says:

    Thanks for the amazing site Jim. It is a great source of good and practical information about the power supply and the problems with the design of the Apple. I have an iMac G5 20″ 1.8Ghz, the original model; and like you say I found several damage capacitors, but I have the same problem with the diode #10 T2D 49, and my question is, What diode is good for the power supply? Or do you know what diode is used? Thanks a lot and congratulations for the site.

    October 19, 2010 at 3:29 PM
  • Jim Warholic says:

    Hello Kris,

    I was not able to successfully track down the replacement for the diode. I am not sure what the value of the diode is.

    October 19, 2010 at 4:43 PM
  • Dagoberto Castro says:

    How do I turn on the power supply without using the computer (connector P1 is unplugged).

    Just for testing purpose. I know that pin 15 on P1 connector is for On – Off, but what do I do with this pin?

    October 28, 2010 at 5:40 PM
  • Jim Warholic says:

    For how to measure the iMac G5 power supply voltages, refer to the directions on the iMac G5 power supply voltage measurements and information on what pins have what voltages.

    October 28, 2010 at 7:38 PM
  • Choice_Computing says:

    Great site… stumbled upon it yesterday and been on it since. I’m new to working on macs, right now I have a IMAC G5 17″ A1141. Power it up and you get the chime…. gray screen.. then apple logo.. for bout 30-45 secs…. then the whoosh of the loud vacuum fan. This will stay steady until i do hard shutdown. From what I have been reading it could be HD, POWER SUPPLY, BOARD….. I have it disassembled now. HD tested good, haven’t multi the power yet.. any suggestions?
    One more question… does mac repair evaluate, if they do, what is the cost?
    PROPS again for all solid info you offer on this site.

    November 19, 2010 at 3:16 AM
  • Jim Warholic says:

    Thanks for the accolades.

    First off, I would inspect the MOB caps. Look for any signs of bulging. Even slight signs of tops of capacitors that are not completely flat, is a sign of bad caps. Refer to my article on the Apple iMac G5 Logic Card repairs.

    Then, certainly you would need to inspect the inside of the PSU for bulging capacitors too. Note that both the PSU and the MOB caps can be bad at the same time.

    As you said, it is also a good idea to check the voltages of the power supply unit. Refer to the iMac G5 power supply voltage measurements and the quick and easy procedure for turning on the PSU that I have posted in my PSU measurement article.

    Also, it is a good idea to reset the PRAM and the SMU per Apple’s procedure. Note there is a link for the PRAM reset procedure in that article. Note also, that Intel based Macs have a different procedure for resetting what is referred to as the SMC, System Management Controller.

    As far as Apple doing a repair evaluation, yes they will perform an evaluation of your computer. However, it is typically an expensive module replacement level fix with Apple. In essence, they will tell you you need a new mother board or power supply unit, or both. Keep in mind, I have heard these types of quotes end up being quoted 600 to 900 dollars for a repair from Apple. Apple will not attempt to fix it down to component level. Apparently, we live in an electronic disposable society with Apple. They would much rather you buy a new computer.

    Try a do it yourself repair and save a ton of money. Worst case scenario, is you spend a little bit of money and it doesn’t work. However, the upside potential is very very promising. The success rate is extremely high on these do it yourself Apple iMac G5 repairs.



    November 19, 2010 at 10:52 AM

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