Siglent SDS1104x-e intermittent glitches, then dead, now brought back to life

[maxwell3e10]

I have an SDS1104X-E that has always been kind of glitchy and sometimes would freeze. Other times it would get stuck on boot and I used the USB recovery stick to fix it. Now the recovery method doesn't work, it tries to read the USB, but then has a little relay click, all lights flash on and it gets stuck.

So I opened it up and started checking voltage test points. The +5V volt was not working, the one controlled by TPS7A4501, and the solder around the regulator looks discolored. I checked, the 5 volt rail is a dead short (0.1 Ohm). I already unsoldered the capacitors right next to it, but that wasn't the problem.

Any suggestions for other places I should look for a short?

[tautech]

Oh yep that would do it.  Subbed while you work on a repair.
  You give this unit for learning rather than take it for the warranty repair you’re entitled to.

[maxwell3e10]

Nah, never used a warranty for anything!

Found a short in a tiny capacitor (CA43 in the picture, inside CH1 shield). Applied 0.1A to the 5V circuit and measured the voltage  in various places on the board until found the lowest voltage that is still near positive rail (which was around 20 mV). For this it is helpful to put a 1 kOhm resistor across voltmeter leads, so readings are more stable. Then verified the component by putting a little drop of isopropyl on it and watching the voltage change. Without that capacitor the scope starts just fine. My guess is that the faulty capacitor and the 5V regulator have been fighting a tug of war until the capacitor won.

[tautech]

Very cool find, good work ! 
Hopefully I'll have the exact cap specs for you in a few days.

[maxwell3e10]

Thanks. It's probably a 0.1uF bypass capacitor for ADA4932 ADC driver. But I wouldn't try to put another one in, had a hard enough time getting it out. At least with a cursory check the transient behavior of CH1 does not seem to be any different from other channels.

[tautech]

Thanks. It's probably a 0.1uF bypass capacitor for ADA4932 ADC driver.

Yep seems so.
From Siglent records:
Package 0402, capacity 100nF, withstand voltage 16V, material X7R