Tag Archives: Repairs

Repairing an iMac Power Supply

A 24″ iMac that wouldn’t start up came in for repair.   Pressing the power button got the fan to briefly run then shut off.  It never reached the point where there was a happy (or sad) chime.  The owner’s first inclination was to toss the computer after we wiped the hard disk but I told him we could probably get it running for the cost of a new power supply (around $75).

Using the always great disassembly instructions at ifixit.com, I got the front bezel off the iMac and checked the logic board diagnostic LEDs.  LED 1 was on and LED 2 came on briefly when I tried to start the computer, indicating that the logic board was probably fine and the problem was with the power supply.

Several disassembly steps later I had the power supply board out of the iMac.  From a quick visual inspection, I could see that some of the  2200 µF capacitors were leaking a bit and one had developed a considerable bulge at the base.  Maybe we could do a cheap repair here?

I clipped the four suspicious caps out (to get an accurate measurement) and checked them with my Fluke 179 multimeter–quick side story:  this DMM is so rugged that it survived a total loss house fire with only minor cosmetic damage.  All the capacitors were out of spec but interestingly the one that looked the worst actually measured closest to good.

Easy peasy fix, right?  LOL, not exactly.  This board uses lead free solder, which is a total pain to remove.  Even with my trusty Hako soldering iron cranked up to 800º, the PCB’s heavy copper traces made it a challenge to keep the solder molten long enough to suck it up with a desoldering tool.  An hour of determined effort and cussing later I had the old caps out and the through holes cleaned out.  (I needed to ream most of the holes to get the last bits of lead free solder out).  Four new shiny black capacitors installed without any drama.

Shiny new capacitorsAll LEDS Normal

I reinstalled the power supply module and the iMac started normally with 4 LEDs lit on the logic board.  I also installed a new button battery while the iMac was open.  Total cost of repair: under $2 🙂

If I were to attempt a similar repair again I wouldn’t bother with trying to remove any components from the circuit board because of the lead free solder.  The job wouldn’t look as pretty, but it would be a lot easier to just leave the old leads in place and solder new parts onto them.

An excellent SSD upgrade

I was tasked with upgrading 36 aging corporate desktop computers (HP model DC5700) to defer the next hardware refresh by 2-3 years.  Bumping the RAM to the maximum 4 GB didn’t result in a satisfactory speed improvement so I decided to explore Solid State Disk (SSD) options.

Users store their files on networked home directories, so there wasn’t any need to expand the PC storage much beyond the stock 80 GB.  Based on user reviews, size and price, the 120 GB Samsung 840 EVO-Series looked like a great fit. (These are also available in 250 GB, 500 GB and 1 TB capacities).  It’s 3-year warranty also aligned perfectly with the planned remaining life of the computers.

I fully expected to have a few issues to sort out on a test system before I could turn over the project to a junior tech for deployment.  I was pleasantly surprised to discover the bundled software is remarkably efficient and user-friendly:

  1. Boot Windows and log in as a local administrator
  2. Connect the SSD to the PC using a SATA to USB adaptor cable or drive enclosure
  3. Run Samsung’s Data Migration utility to copy the PC hard disk to the SSD
  4. Shutdown the PC and replace the hard disk with the SSD.  (Don’t waste money on a 2.5″ to 3.5″ mounting adapter.  A piece of double sided foam tape is all you need to secure the SSD).
  5. Run the Samsung Magician utility to tweak performance settings

Hands-on time was under five minutes per PC and it took around 20 minutes for the migration utility to copy everything off the hard disk.

The performance improvement is amazing.  Boot time reduced from 3+ minutes to under 30 seconds.  McAfee full antivirus scan, which previously rendered the PCs almost unusable when it was running, is now barely noticeable.

Tremendous bang for the buck and unconditionally recommended!!!

Reviving a drowned laptop

My friend spilled a glass of water into her 13″ MacBook Pro.  She had tried (unsuccessfully) to dry it out by sticking it in a bag of rice, followed up by a blast from a blow dryer.  The laptop would not turn on at all.  The battery was installed but fully depleted.  At that stage it was too late for her to heed my general advice for soaked electronics:

  1. Turn it off
  2. Remove the battery, if possible
  3. Open the case, if possible
  4. Seek professional advice before attempting to turn it on again!

Oh well . . .

With slim hopes of success, I set out to see if the laptop was salvagable.  As usual, iFixit had excellent teardown instructions.  Typical of Apple products, taking the MacBook apart was a lengthy, tedious experience.  I got the case open and shook out enough rice to make a batch of paella.  It seemed that the water had migrated directly to the bottom of the laptop where the logic board is.  So the worst case scenario looked like a new logic board, which would run around $650 unless we could find a better deal on a used part.

One hour and a couple dozen screws later the logic board was out.

macpro-logicboard

As far as I could tell there were no burned components on the board, so perhaps the apparent short was correctable.  However, there was white corrosion/residue present in several places.

macpro-logicboard-1

I managed to clean the board up with a new medium-bristle toothbrush, working carefully to apply just enough pressure to dislodge the corrosion but not enough to pop off any of the surface mount components.  I reinstalled the cleaned up board, reassembled the laptop and crossed my fingers.

happymac

Voila!  It’s alive!  One happy Mac and one happy friend.