Faytech FT0150TM touchscreen turning on and off - fixed

[dougg3]

I've been dealing with this 15" touchscreen monitor from the early 2010s. Over time, it has become more and more difficult to power on. As soon as a video signal comes in, the Faytech logo appears on the screen and then it goes black. Then a couple of seconds later the Faytech logo comes back up on the screen and it goes black again. This process repeats over and over again. Eventually if I leave it on long enough, the video display finally comes up and it works fine. The longer I leave it turned off, the longer it will boot loop before working correctly again. I tried a different AC adapter but it had the exact same problem so I concluded it's something in the monitor itself.

I opened it up and immediately spotted three iffy-looking 470 uF, 16V capacitors near the DC in jack. The manufacturer/model of these caps is Chong CD11X. The main PCB is identified as: NS_FT81A_V1.2_20120818



Two of them were looking a little bloated. I removed them and measured their capacitance and ESR.

• Top capacitor nearest to the power jack, doesn't look bloated: 425 uF, ESR = 0.09 ohms.
• Next lowest capacitor, right next to the white connector with black wires, a little bloated: 411 uF, ESR = 0.91 ohms
• Bottom capacitor, looks quite bloated: 400 uF, 0.39 ohms

The two that look bloated definitely had higher than normal ESR. All three of them were a bit on the low side in terms of capacitance spec. Definitely within +/- 20% though. I replaced them with Nichicon caps that measure about 500 uF and 0.03 ohms.

After replacing those three caps, the monitor works perfectly again! I probably should have replaced all of the smaller ones too, but I guess I'll leave that for the future.