Linksys/Cisco ATA power adapter repair.
Step 1: Identify the Problem
If you use VOIP (telephone over internet), then you most likely have one or two telephone adapter boxes (ATA's). I have two and both are Linksys 2102 models. Their power adapters supply 5 volts. When my first power adapter failed, my box appeared dead with no lights on. I found out that the problem was the power adapter by testing the box with the power adapter from the other box. Please note these boxes are very picky and will probably not work with just any 5V power adapter.
Step 2: Fix It.
I cut open the case of the faulty power adapter and found that the problem was caused by capacitor plague. A few years ago there was a whole batch of faulty capacitors that were used in various electronics gadgets, including TV's, satellite receivers, power adapters etc. When these capacitors fail, as they inevitably will, the gadget stops working or exhibits weird behavior. Thankfully, it's mostly an easy fix. Identify which caps are bad (usually have puffed up tops), then replace the culprits with new caps of the same value. On my power adapter, the 2 caps on the right (pink painted) are bad. I replaced them with new caps having the same value (680uF, 16V, 105C). They just cost a few cents. I did have to desolder the bad ones and then solder new ones. As you can see, the new ones I bought were taller, so I cut 2 holes in the top half of the adapter case to accommodate them.
Step 3: Finish
With the case closed up again, I just wrapped electrical tape around it to cover the capacitors and to hold the case together. My ATA works well now. The one I had repaired before has been running with no problems for more than a year. If you have a similar problem, I hope this instructable helps.