Hi, i have a Kikusui COS5020 oscilloscope and channel 1 on it doesnt work
(not getting any trace at all). Does anyone know where to get the
schematic/service manual for it? (I have found a paid site but ill try and
see if i can get it free first).

Also can anyone point me in the right direction where to look for the fault?
When no channel is selected there is a faint unfocused mark on the screen
which stays there when ch 1 is selected so this leads me to believe that
maybe there is something wrong with the input selection section.

Hope that made sense

Cheers