Hameg HM1507-3 oscilloscope

[doncia]

Hi, all of you.  I've been working with this scope for a long time now, but lately I noticed that channel one was a bit unstable.  Consequently the problem evolved into having ranges of 5V and larger not working at all.  The scope internal relay is working as I can hear the click and compared to channel 2 it is switching at the right range change, however the display goes to a flat line at the 5V range. Anyone can help please?

[oldway]

Welcome on the forum 

It is probably a problem of bad contacts of the relays.
Here is the diagram of the front end of your oscilloscope.