Hi to all.
I have a TDS684B scope presenting a "vibrating" waveform. It is in vertical and horizontal directions, as another signal were added to original one. This happens in 4 channels.
--in self test it pass, no message errors or fails;
--this shake appears to be more intense in higher frequencies input signals;
--without input signal the horizontal trace is fixed;
--this shake is randomly, not a repetitive pattern;
-- the 25 volts power supply is presenting a ripple as noise-it reaches 0,5Vpp sometimes. The other supllies are OK. I did not find yet the reason for this ripple in the 25 volts psu, it seems to be in the first rectifier/multivibrator part. Capacitors are OK.
--there is no schematics.
Anybody has a tip to help me?
Thank you in advance
Dirceu