Yokogawa DLM2024 video problem

[rob10k10]

Hey guys!

I'm working on Yokogawa's oscilloscope that I bought with video problem. When I tested it first time, the image was always abstract, sometimes changing the pattern. The image is the same on the onboard video and the VGA output.

I checked the power supply and it looks good (no ripple). Looking at the board I found a FPGA that's responsible to generate both video outputs. I realize too that this FPGA warm up a little (around 60°C) so I asked to a friend to do a reballing process on the FPGA, guessing the heat generated some connection problem between the IC and PCB.

The reballing process solved part of video issues. Now I can see the video normally during some minutes (or seconds) if the oscilloscope is cold (ambient temperature). After some time when its on due the heating the image gets abstract. If I turn off and turn on after some minutes, works fine again.

Any guess to solve this problem? I attached some pictures of the main board and video problems. I didn't find service manual or schematic.


Robinson.

[rob10k10]

There are some other interesting details: some menus has weird backgrounds (images attached).

[Gominalo]

Looks like corrupted RAM, check if it has a self ram test.

[rob10k10]

There is only ROM test.

[Gregory]

I thought of bad ceramic capacitors or BGA soldering problem..
But the broken menus indeed sound like a bad memory chip