hitachi v-550B problems

[mj21]

recently i bought a Hitachi v-550B 50MHZ scope of eBay. it powers up and there is a trace. when i feed the 1khz square wave from the scope to channel one if the volt/div is below 0.1mv i get overshoot and undershoot in the square wave, if its above 0.1 i get kinda of a square wave. picture 1 and 2

now channel two is kinda mad to, i get whats is in picture 3, regardless of the voltage division
 i have checked the 1khz wave with my rigol scope and it is a perfect square wave.

does anyone know what could be the problem?

thanks

[Chryseus]

Compensate your probes maybe ?
There should be a trim pot on the probe handle or near the BNC connector.
Adjust it until you get a nice flat on the square wave.

[mj21]

thanks, i tried it and still the same thing. funny think is when i connect a signal to the inputs the ground wire makes no difference in the signal integrity. usually if i don't connect the ground wire the signal is all over the place, can there be a problem with the grounding?

[grumpydoc]

The first picture could just be probe compensation, the high frequency response is a bit too high but I'm slightly suspicious that the HF compensation in the 'scope's attenuator is off because it shouldn't really depend on the attenuator setting.

The trace in the third picture looks like the low frequency response is too low, such as you'd get if it were going through a DC blocking cap. Do you have your AC/DC coupling switch set to DC and if DC have you checked that the switch works and you get a DC path through to the 'scope input.

Scratch that - you get a different trace in that case, looks more like a cap in parallel with your signal (so more low-pass than high pass).

Really you could do with a decent square wave source that will drive a 50ohm termination because then you can check the 'scope without worrying about getting the probe comensation right.

As you have a 2nd 'scope if you get a decent signal source you can trace it through the input channels on the Hitachi to see where it all goes pear shaped.