Tektronix 2235 channel 1 trace unstable

[Evoroadster]

Channel 1 trace is unstable in AC, GND or DC position. Applied signals are good but bounce around. Channel 2 is rock solid. Before I dive into this does anyone have any recommendations are where to start.

 

[rjenkinsgb]

Operate ALL the switches and controls a few times. A tarnished contact can cause all sorts of odd effects & working the switches can clean the contacts.

 

[ahsrabrifat]

You can swap the probes between Channel 1 and Channel 2. If the instability follows the probe, the problem is with the probe or its connection. If the instability stays on Channel 1, the problem is internal to the scope (or the input jack).