Electronics > Repair

[Solved] TDS1012 (TDS1000/2000) can't display sharp vertical line

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samoEEVB:
I recently purchased a broken TDS1012 to practice repairing.
It had some water damage and a short to GND at a decoupling capacitor (array) for the acquisition ASIC, it wouldn't boot when I purchased it and the acquisition ASIC would go as hot as 130c when powered up due to the short.

I cleaned up the water damage and replaced the capacitor array, it can boot up and pass power-up tests.
However, now it seems it can't draw sharp vertical lines such as rising/falling edge of a square wave:


I can see dots moving vertically on the edge though, so this feels like it could be a vertical data display problem.

Some information I can provide now:

* It's not an LCD display problem, I've tested with a known good display.
* The water damage actually is right around the circuit at the output connector to the display, it corroded so bad that it created an invisible break at the middle of the resistor and capacitor array of data line 1. Causing the display to miss one vertical line in a pattern. I had to manually bridge it to repair this issue.





The scope can display the rising/falling edges if I switch horizontal window to a shorter period, so it seems the problem is more like it can't display a "long" single-pixel-wide vertical line.
I've compared it to a known good scope and the acquisition data seems to be OK although the ASIC had been heated up to 100+c multiple times due to the short.

I double-checked that the four data lines to the display are OK. (There are no breaks, at least.)
Now I'm not sure how to proceed with pinpointing the exact source of this problem and could use some suggestions from experienced friends here. It would be nice if someone could share the knowledge of how the acquisition data is drawn on the display.

Fingers crossed for it to not be an ASIC problem! :-BROKE

 

Greybeard:
Are you sure, your display setting is "VECTORS"?

Push the button "DISPLAY".
Set "TYPE" from "DOTS" to "VECTORS"

samoEEVB:
Doh!  :palm:
Thanks a bunch Greybeard, I can see the vertical lines now after setting the option to vector. That's one more scope saved from the dumpster 8)

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