I had repaired and upgraded a TDS7104 using the excellent info on this thread. It has been working perfectly for months, but just yesterday a very strange fault occurred.
When the record length is set <= 2000 samples, everything works perfectly. As soon as I set the record length > 2000 samples, all the traces simply disappear and the scope responds very slowly to changes in settings. The Windows UI and front panel LEDs etc are still responsive, but the trace and trigger markers move very slowly.
Weirdly, slightly larger record lengths (up to 5000 as far as I can tell) appear partially when I enable horizontal zoom. (See attached picture for a screenshot of this behaviour - notice the trace is invisible in the top window). Without zoom enabled the trace is invisible.
Enabling FastAcq also induces the same fault symptoms.
The fault first occurred when I was using the scope as normal, record length was some large value. Suddenly all the traces froze and the scope became unresponsive. I rebooted and it is now permanently as I described.
I have tried restoring default settings, reinstalling the TekScope software and using an old, previously working hard drive. This has made no difference. Diagnostic test returns all pass, supply voltages all good, NVRAM battery is fresh.
I am running Windows XP with a SU810 motherboard, which I upgraded from the original Bl440ZX/Win98, but it has been working perfectly with this configuration for months.
It almost seems to me like some kind of display rendering issue when there is more than a certain number of points on the screen. Don't know what to make of that though...
I can't make any sense of this. Has anyone else seen this problem? Does anyone have any ideas for how to even begin troubleshooting this? I'd be very grateful for any ideas.