A few weeks ago my 20″ Apple Cinema Display decided to stop working. Instead, the power LED flashed a short-long-short error code indicating that there was a fault in the power brick. A quick swap with another display revealed this was not the case (otherwise this would be a very short post).
After doing a bit of searching there were two solutions to the problem. One of the ‘fixes’ is to block a voltage sense pin on the power connector. It seems in many cases this will let the monitor start-up, however doing this will mean that the monitor is running at an unsafe voltage. The other solution in many cases was to replace a faulty voltage regulator. Because most of the answers I found focused on the 23″ display I couldn’t be certain until I took apart my monitor.
I feel rather fortunate in that the voltage regulator that was the source of the display not turning on. Instead of putting out the expected 3.3V, I was able to read a little over 4V on my multimeter. This was very similar to a number of other posts I found (search for “1117-3.3sj”). Annoyingly the regulator was in a DPAK (or TO-252) package, and it is one of those things that I can’t imagine many people would have lying around. I couldn’t find a data sheet for the particular regulator, so I found a replacement regulator that was overkill for the application. I ordered an LD1086 3.3V 1.5A from Digikey on Friday and got it in this afternoon.
Desoldering the old regulator was time-consuming. I snipped the two small leads off and desoldered those first. The larger tab took a lot of time and heat before it came loose. I then wicked away the excess solder and installed the new regulator.
I ended up with a little excess flux, but overall the new regulator went into place easily. I was then able to test and see if I had fixed the problem.
Powering up the monitor a green LED indicator light up, the backlight came on, and upon testing the output voltage at the regulator I was happy to see around 3.3V. I took a little time to inspect the rest of the board while I had the monitor apart and have included a gallery with all the pictures. Re-assembling the monitor went quickly, and the $1.50 for the regulator sure beats buying a new monitor!