Hi Nenad,
I did, I uploaded a photo here:
/g/TekScopes/photo/89504/0?p=Created,,,20,2,0,0
this was taken with SCAN at approx. 21h position, so that "Morse code" could be seen.
Your photo reminded me of a modification I made in my 7S12. See here and surrounding messages:
/g/TekScopes/message/96331I'm not sure your "morse code" problem is related to it and also not whether it's related to the unit not showing waveforms.
W.r.t. sensitivity for DC input (did you try?) I forgot that the setting of S901 "Correction Memory Switch", see page 2-5, is important. For now the best way is to set the switch in the rear (OFF) position (as long as you don't have a pulse generator head).
Here is one more attempt to show that the preamplifier responds to the strobe pulses.
With a DMM attached to the front panel Vertical Out connector you can see that Memory is slowly drifting when no strobe pulses are generated. You can set the S-53 for free running when Level is roughly midway and Stability cw, and stop and start free running by slight rotation of the Level knob. You don't need any signal for this and you can try it at different Offset levels. During free running the DMM will reflect the vertical position of the visible trace, and will listen to variations in Offset. When you turn off free running, the trace gets blanked but the DMM still shows the trace position. You will see the DMM reading slowly drifting away in some direction. When you turn free running on again, the DMM reading will immediately jump back to the normal value. The trace should reappear immediately at the previous vertical position. If you don't want to wait for drift you can change Offset while free running is off; the trace should immediately be at the new position when you turn free running on again.
Albert
