I have also a bought a few of these ‘broken’ units the past years. Spend around 800Euro’s in total on all the units. I had 2 complete units, one even with probes and power supply, one unit with only the front cover with display and 2 units with only mainboard and shielding. From all these parts I was able to make 2 complete working units, a 199C and a 196B. The 199C I use almost every day at work and is working like a charm. The 196B unit is still a little bit faulty.
So, what was wrong with these units? They basically have the same problem: it is a lose contact under the BGA (D-ASIC, it is a custom made ARM processor). The one in the 199B started working after some pressure applied to the D-ASIC, so I reflowed it again with a hotair soldering gun and a preheater. I did this also with the one in the 196B, but this one still has a problem with a soldering joint or other contact problem. BTW: in the service manual, par. 7.5.12 RAM Test, there are instructions how to test the RAM/FLASH module. If my 196B is not working, this test fails, indicating there is a address line problem. So I think I need to remove the D-ASIC, reball it and try to place it back, but that is a hell of a job. But the other mainboards are more problematic. I did a thorough investigation on one motherboard, which I could not get to work, even after removing, and reballing the D-ASIC. So I checked all connections under the BGA with an ohm meter and noted the ones that had no resistance at all. I looked up these suspicious pads in the schematic and measured (with a continuity test) if the other side of the trace was connected. There was no connection. Further investigation revealed that the via under the BGA was faulty. Some via’s were ‘repairable’ by placing a very thin (tinned) copper wire into the via (with some flux) and then heat it with a soldering iron. Some of the connections were indeed restored, but some not, so I never continued this way.
But to make a long story longer, I think the 19xB/C series scopemeters have a problem with their BGA soldering and there PCB’s. And I think the unit of Hugoneus can also have this same problem, which, maybe, turn up sooner or later.