Sir, if you used the probe to test, please use a non-metallic tool to adjust the trimmer capacitor of the probe for the fattest square wave being displayed on the oscilloscope.
In addition, replace a connecting line to try.
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Probes were adjusted in internal square wave(5V@1KHz) and shows right square wave. Only on 150Hz it shows wrong form of signal. And i switched probe from one channel to another - forms of signal didn't change.
Could you give me links to datasheets for that components and places where i should replace it in scope?
I have found AQY280SX http://www.mouser.com/ds/2/316/panasonic_AQW,AQY280,282,284-347496.pdf is it correct?
Can't find what is U100.