Zenith DTT901 & Insignia NS-DXA1-APT DTV converter box: Cold Power-Up Problem FIXED

[wb2mep]

This seems to be a common problem with these LG Zenith & Insignia DTV converters. Mine started failing when it was less than one year old: It was unplugged while I was on vacation in the winter, and when I got back, it was dead when I plugged it back in. Eventually I got it to come up by repeatedly plugging/unplugging until the red LED came on. Later on I had a problem where the
blue LED would come on for a few seconds then turn back to red, when it was cooler than usual in the living room. (< 78 degrees, I live in Florida) I had the problem again this weekend, so I dug into it. It has all the symptoms of a power supply capacitor problem, but the solution wasn't very obvious. The power supply puts out 5.4, 3.4, and 2.6 volts (voltages are labeled on the board at the output connector) The 5.4 V was good, but the 3.4 and 2.6 V were low and the box was dead. Eventually the voltages came up, and I got the red LED, but when I hit power, the blue LED came on for 2 seconds and went back red, and my voltages were low again. I pulled the power supply board and measured ESR on all the electrolytics. They seemed normal, so I put the board back in and the box powered up.
I got my can of freeze spray, and hit each of the 'lytics, and when I hit C123, the box shut down with a red LED and the 3.4 V dropped. C123 is a 1000 uF, 10 V electrolytic. Easy to find, the component numbers are printed on the board. This cap measured only 0.23 ohms ESR, which I wouldn't normally consider bad (it did go up to 0.42 ohms when I cooled it with the freeze spray).
It wasn't bulged or leaking, and looked brand new when I removed it from the board. It was a Chinese-made Sam Young brand cap. I replaced it with a Nichicon 1000 uF 10 V, 105 deg C, low-ESR cap and my box is working fine again.
These Zenith/Insignia DTV boxes were the best ones in my opinion, and definitely worth repairing, especially since you can't find new ones any more.