[SOLVED] Hantek MSO5074FG - stuck at self-cal step 34/66

[aandrew]

I have one of these and while doing some small-signal measurements (power supply ripple) I've noticed that the scope seems to have a ~80mV offset at the 50mV/div scale. This offset is present on AC or DC coupling (not when the coupling is set to GND).

I thought perhaps I should run a self-cal so I disconnected everything from the front panel and ran it, but it got stuck at step 34. Hantek says it should take about a half hour but even after running it overnight it's still stuck at the same step. They are unwilling to give me any information to try to resolve this on my own but I know there are some people here with a lot of experience with hacking this device so perhaps some of this info might be floating around eevblog...

Does anyone here know what the various self-cal steps are or more specifically how to get past step 34?

[aandrew]

So I opened up the scope just to poke around and immediately found a problem:



After replacing all the caps in that section (the electrolytics sprinkled around the rest of the board all looked fine) the unit powered up and I did a self-cal which completed successfully! I guess whatever is going on around step 34 was waiting for the supply to be quiet and with those toasted, bloated caps it could never get there.

So I did the natural thing next: I replaced the HEF4052s with CD74HC5052s from TI (better analog bandwidth), installed the missing ethernet components and added the JTAG headers.