RTB2002 Repair/Diagnose

[CrazyTiger]

Hi,
I got this RTB2002 70MHz version from a local university, apparently, it was found faulty. My initial response in the back of my mind was "jackpot, I am getting something free possibly with a busted fronted from misuse, simple repair".

What I got was totally a different case. First, check I found the unit was looking new, no scratches boots normally. However, the trace is full of noise on both channels.

Here is a snapshot with the unit measuring 10MHz output from its own aux output.



On very rare occasions, the unit works ok for a few seconds, clean signal, no noise.

What I have eliminated so far:
0. Self-Alignment passed with no error, though the noise is still there.
1. Frontend input section, they look and measure identical on both channels, the input impedance is measuring 1MOhm and the multimeter function measures spot on.
2. Trigger section looks good and the counter is measuring spot on, so I believe that is also ok.
3. Due to the nature of the failure being intermittent, I suspected maybe the 10 bit ADC chip is not soldered properly, so the entire board went into a reflow oven as well.
4. I have checked all the local dc-dc converters, they measuring correctly, I am yet to check the noise on the local supply though. need an isolated scope for that. 
5. LMK04816 was found to be running hotter than all the chips, replaced that. This chip is providing the necessary clock out to both the ADC Chip and ACQ FPGA I believe, The chip is still running hot after replacement, will have to look deeper into the section.

So far, I have made zero progress

Next up, what I will be looking into:
1. The section of the board from the differential output to the ADC chip.
2. Measure ripple/noise of the local supplies, there are tonnes of these.

Any other Idea on what else I can look into?
More pictures coming

[goaty]

Maby ram issue or fpga.
Also if test pass, maby displaying only related ( copied ram content from acq to display processor)

Need schematic 😁