Category 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, 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.

Did you hear about the Rabbi who didn’t charge for circumcisions?

He only took tips!

I don’t charge friends for repairing their electronics, which I’m always glad to do and genuinely enjoy.  But I’ll happily accept a bottle of wine as a token of appreciation.  Sometimes people are really happy to get their stuff fixed.

Look at the pile of swag that my overly generous friend laid on me for putting a new LCD screen in her MacBook Pro!!!


That’s two bottles of (very good) wine, a trivet from Williamsburg, a rotary cheese grater and a bag of tasty nuts.  Youza!

Six hacks from 5 grams of Sugru

If you’re not familiar with Sugru, you should be.  It’s a moldable rubber compound that can be formed into any shape and cures at room temperature.  Sugru is amazing stuff.

Sugru comes in little 5 gram pouches in various colors (which can be blended together to create new colors).  The contents of each pouch needs to be used pretty much immediately after opening so I always try to batch my hacks/repairs to utilize a full pouch.  This might be my personal best–six objects improved with one pouch of Sugru!


This otherwise lovely set of fish plates had rough, scratchy bottoms.



A few rubber feet later, problem solved!  Tip:  after forming each rubber foot, place the object right side up on a piece of waxed paper and press lightly to flatten and level the feet.  The waxed paper will peel off easily after the Sugru cures (around 24 hours).


Same problem and same solution for this nice Spanish platter.


Now what to do about about an otherwise perfect place to keep a bedroom clock radio?  (The problem is that it isn’t possible to see the “alarm off” button without getting out of bed and kneeling down.)


Well, let’s just add a nub of Sugru to the Off button and feel it instead!!

There you go.  Six objects improved for an investment of a few minutes time and under a gram of Sugru each.


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.


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.


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.


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