Hello! I've searched the forums here and the internet in general, but I haven't found a way to fix this.
The main time/div knob is stuck on 0.1 ms/div on my HP 1742A analog oscilloscope and I can't move it. The delayed time/div knob (the ring around the main one) works fine. The main knob flexes a little, but never clicks into another position. I haven't put too much torque into it for fear of breaking the plastic.
The insides look like
Video 803 with the 1740A, but with an extra plastic cog wheel and its board for the 1742A. None of the plastic gears seem stuck to the boards, and none of the spring-loaded pawls seem to have a problem. It's easy enough to manually move the springs. If you turn the delayed knob a tiny bit, its metal axle moves a tiny bit. But if you turn the main knob a tiny bit, its axle doesn't move at all.
It's very clean inside, except for a little bit of dust. Nothing looks obviously jammed and it doesn't look like there should be anything blocking movement. What do you think I should look for or do at this point in order to try and fix it?
I was able to find
the manual online, but I didn't see this problem in there. I'm familiar enough with digital o-scopes, but this is my first time with an analog one. I'd be happy to provide any additional information as well.