David,
Try searching "7T11 Failing Trim Caps" in the archives.
This contains information on shifting trace problem.
Joe
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--- In TekScopes@..., "David C. Partridge" <david.partridge@...> wrote:
In equivalent time, sequential mode, the trace is shifting left as I rotate the time/div knob.
All measurements were made on the 50nS sweep range with the timebase triggered from Pulse Out.
Looking at the signal at TP286 which is the output of the TTH circuit, I see:
Time/Div Start V Stop V Delta V
5nS -2.22V -7.82V -5.6V
2nS -2.22V -4.62V -2.3V
1nS -2.22V -3.5V -1.2V
.5nS -2.22V -2.76V -560mV
.2nS -2.22V -2.43mV -230mV
.1nS -2.22V -2.34mV -120mV
50pS -2.22V -2.62mV -60mV (approx values)
20pS -2.22V -2.25V -30mV
10pS -2.22V -2.23V -10mV
Looking at the output of U512A (TP512):
Time/Div Start V Stop V Delta V
5nS -0.1V +5.5V 5.6V
2nS -0.3V +5.3V 5.6V
1nS -0.6V +5.0V 5.6V
.5nS -900mV +470mV 560mV
.2nS -210mV +350mV 560mV
.1nS -420mV +140mV 560mV
50pS -70mV -10mV 60mV (approx values)
20pS -170mV -110mV 60mV
10pS -340mV -280mV 60mV
I don't think the ramp start voltage should be moving down like that.
Can anyone confirm my suspicions and suggest what the fault might be?
Thanks
David Partridge
