So I've come into possession of what I believe is this same instrument and while exploring the features I started to consistently get this ADataH stuck hi error and Acquisition reports Fail in the self test. From looking over the component service manual for the similar TDS520B I deduced that this likely means there's a stuck bit in the bus between the "C" ADC and the associated DMUX which so far as I can tell serves channel 3. Acting on suggestions I've seen to check solder joints on the DMUX ICs I decided to start there. Close inspection revealed a few suspect solder joints on the big QFP so I carefully reflowed some of those, inspected it for bridges and then fired it up. Scope still appears to work, I can get nice looking signals on all four channels but now I find that when I run *any* of the self tests, Processor, Acq, Display or Front panel it will run for a bit and then appears to reboot and display the splash screen that says Power on self tests PASS.
I'm at a bit of a loss here as to what is going on, could a problem I created on the acquisition board cause the whole scope to reset? I would have thought that any fault severe enough to cause that would prevent it from passing the power on self test. There are no new messages showing up in the error log, only the ones from before. The soldering I did on U200 looks fine, although I'm thinking I may xray it when I pull the board to replace the attenuator relays which I know need some attention. Replacing ICs with parts off a parts acquisition board is within my ability but I don't want to risk damage or dump money into what turns out to be a red herring, a used acquisition board would probably cost as much as I paid for the whole scope. Could the self test problem be a coincidence that developed? Seems unlikely as I didn't even touch the processor board. I believe I could swap in an acquisition board from a similar model scope for testing but given this has the 2M option my impression is that my choices of a proper replacement board are somewhat limited. Isn't 2M a hardware option with physically higher capacity acquisition RAM? I have not attempted any power-on probing, having seen dire warnings of catastrophic damage. It's a real ego-deflater to make negative progress, it's still a usable instrument but I don't want to invest in proper probes and such until I'm reasonably confident that it's working 100%.