Hi Brian,
The spot has to jump from the current trace vertical position to the readout vertical position. The undershoot or overshoot will be a fixed percentage of the jump size. If you move the trace (waveform) further away from the readout position then in absolute sense the jumps (say between top trace to readout and bottom trace to readout) will increase - and so will their differences - and the wavy behavior will increase. It will also increase when you increase the displayed signal amplitude (with same vertical centering).
In your 7844 the trimmers to adjust are R1749 and R1764 (for Beam 1), see calibration step G-6e, page 5-33, "LF COMP 1" and "LF COMP 2". I think you'd best use the same setting for both, though I didn't see such mentioned at first reading.
Albert
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On Fri, Dec 31, 2021 at 07:15 PM, Brian wrote:
Hi Barry , thank you for the reply . I had heard / seen it mentioned that it
was LF compensation being way off causing this but like you I hesitate to just
blindly adjust a pot and see if it makes a difference . I had looked at the
circuit and seen that some of the pots one might be adjusting are in series
with the dreaded tant capacitors , I wonder if with that effect when using the
vert position control it means the tant cap is bad . I'll have to tweak the
pot and see then maybe change the tant if none or not enough effect .
thank you?Brian (UK)
