Digitech QC1933 intermittent issue.

[Stuart Coyle]

I'm having issues with my old DSO, bought from Jaycar as a QC1933 which I believe is a rebadged Atten (at least the power supply has Atten on it).
Yes, I know I should just buy a better scope but I have an in house accountant that I have to pass purchases by (wife).

The scope will randomly freeze up. Display stays visible but nothing works. It was crashing after about a minute of operation.
I have just pulled it apart and given it a good look over, clean and check of power rails. All +/-5 and 12V rails seem
steady, even when it freezes up. (it would be good to have a scope to check that properly...)
The power supply seems fine.

I found a dodgy solder joint on a 12V regulator, looks like one has been replaced at some time, which is odd since I bought it "new" from
Jaycar. I resoldered the regulators just in case, the solder on them was looking pretty dry.
Anyway, I cleaned it up, put some contact cleaner in the rotary encoders and such.
I ran it for a while out of the case and it crashed a few times. Then after a while it ran fine, had it heated up enough or something?
It's back together again and has run for a few hours without an issue. I don't trust that it is actually fixed.
I'm at a loss for what the problem might have been. Anyone with an idea?

[m k]

Intermittent contact problems are nasty.

If you can use it when it's open you can try cooling and heating from here and there.
That's not much, but it's pretty much what you have, you can also try knocking stuff.