Hi Mac,
Since your response came so quickly, I couldn't resist to answer before going to sleep:
Barry describes (part of) his problem as follows:
Changing the vertical position of the trace definitely changes the height of the trace
as I move from bottom to top.
Only Channels 1 and 2 exhibit vertical linearity issues
The problem as described by you (Mac) from msgs. 89026:
My first complaint is the vertical channels 1 and 2 have a sawtooth noise on the trace.
Changing vertical position causes the sawtooth to appear and it grows as the trace is moved farther from center.
I interpreted Barry's description as a vertical trace compression problem, whereas in Mac's, I imagined a sawtooth superimposed on the trace with position-dependent amplitude. The compression (in CH1 and CH2) is the signature symptom for me to suspect U400. I don't want to make U400 into a scapegoat any more than necessary... -;(
Computer is going to sleep now, I'll follow within 20 seconds!
Raymond
Raymond Domp Frank