Dead Siglent SDS1104X-E Oscilloscope

[thunew]

I'm trying to troubleshoot a dead SDS1104X-E I received from a friend third hand, they inquired about the warranty but the scope was sold by an unauthorized retailer so no luck there. It was working for a over a year before this issue began.

When I turned it on it operated normally for a minute or so but the screen was slowly covered up by white lines until it went completely white and all buttons and knobs stopped responding. Now when powered up I hear the initial relay click followed by all the button LEDs lighting up, however the screen remains off and there are no further relays or LED changes like my second working unit goes through during boot.

I opened the case up and measured all the available test points, voltages all seem to match the values written on the silkscreen and there's no crazy ripple or anything. None of the caps look bulged. I also tried reseating the LCD and button ribbon cables to no effect. The pins on the serial debug port go high when power is on but I haven't observed any data being transmitted on it. IR cam doesn't show anything on the PCB getting unusually hot.
I haven't been able to closely inspect the PSU (the only screws in the scope my torx drivers are unable to reach) but it seems to be working so I'm not that suspicious about it.

Has anyone else experienced issues like this before? I assume its something nasty with the flash or zynq to cause it to fail before it even begins booting.

[Haenk]

Bad solder joints, maybe on the CPU?

[thinkfat]

It can be accessed from the network, does that still work?

[tautech]

Work through the troubleshooting section in the service manual:
https://siglentna.com/download/6149/

Most unusual, I have SN# 0012 and it still works perfectly. 

[tautech]

IIRC there's another display connector behind/under the chassis that the display ribbon cable terminates into.
If you remove the screws that hold the chassis in and unclip the cables that connect to the mainboard you should be able to lift the chassis out.....maybe disconnect the fan also I don't remember.
Then you can reseat the display cables but be gentle with them and inspect them for corrosion. If necessary clean them gently and carefully with an eraser.
Take your time and be carefull with the ribbon cable retainer clips.

[thunew]

Work through the troubleshooting section in the service manual:
https://siglentna.com/download/6149/

Thank you for the link tautech, the copy I found while googling lacked the diagrams and useful sections at the end.

The rails all seem to meet the ripple spec, if marginally. Miraculously the scope began booting again the other day, sometimes rapidly displaying the original issue and sometimes remaining perfectly stable. Enough so that I was able to run a firmware upgrade and self cal. It doesn't seem to have improved the situation at all and it still regularly locks up at boot for a dozen or so attempts.

It can be accessed from the network, does that still work?

Unfortunately no, it stops responding to pings and fails to load the web interface once the display disruption begins.

Interestingly the screen recovers over time and the white lines disappear. The scope continues to correctly display live waveforms although the buttons, knobs and network remain down. Any ongoing data collection, statistics or onscreen measurements freeze however.

[tautech]

Work through the troubleshooting section in the service manual:
https://siglentna.com/download/6149/

Thank you for the link tautech, the copy I found while googling lacked the diagrams and useful sections at the end.

The rails all seem to meet the ripple spec, if marginally.

Exactly how did you measure ripple ?
As it's a SMPS you need use another scope.

Miraculously the scope began booting again the other day, sometimes rapidly displaying the original issue and sometimes remaining perfectly stable. Enough so that I was able to run a firmware upgrade and self cal. It doesn't seem to have improved the situation at all and it still regularly locks up at boot for a dozen or so attempts.

OK so we have a display issue and possibly a PSU ripple. They might be related to dying caps in the PSU.
Can you measure the caps for value and ESR ?

Did you fully remove the chassis and reseat the hidden ends of the display ribbon cable ?