Hello all,
I just got my first oscilloscope today, a Tek 2213, off ebay and was playing with it most of the day using ether the probe adjust signal or signals from my computer's sound card. The square waves from the probe adjust where square and the sine, square, sawtooth, etc. waves from my computer where as they should be too, everything was working fine!
Then... I decided I wanted to clean the unit... The first thing I do is take off the pouch bag on top by removing the two screws that hold the plastic back piece on, one more screw later I had the blue case off to look inside the unit. I got the case back on and then give the front panel a rub down with isopropyl alcohol and Qtips. After fully dismantling the probe I did the same to it, the probe is a "Tek p6006 BNC 3.5 / 10x = 7pf. 10M-Ohms"
After I get everything back together and turned the unit on I tested it with the probe adjust signal, the square wave was not square, It has a triangular spike at the top / beginning of the wave and the inverse at the end / bottom of the wave. I switched the probe to the other channel... same thing... test it with my PC... only thing that looks normal is the sine wave*. After all that I connect another probe that came with the unit, an old looking and worn out RCA WG401A. Everything seems to be ok again.
What did I break???
*sorry forgot, If I remember right... I can flip the switch from AC to DC that's on the vertical mode panel and the wave becomes (more) square.