This is my first post about my first scope that I
purchased recently. I am also not an electronics technician, so please be
gentle with me :-).
The scope is in excellent condition and has been
recently calibrated. However, when using the scope I noticed occasional small
ripples in the traces. I opened the scope and tested the power supplies and
determined that the ripple on all the rails was 2 to 3 times larger than the
limit quoted in the service manual. Consequently I replaced all electrolytic
capacitors in the power supply, except the C906 input filter capacitor, with
Nichicon PW series capacitors. I used the exact same capacity components where
the originals were +/-20% and the next larger capacity where the originals
were -10% to +30, +50 or +100%. I also replaced the four 0.01uF 3000V
capacitors with CDE 940C30S1K-F polypropylene capacitors.
the occasional ripples have not completely disappeared after the overhaul even
though the traces seem to be a bit sharper. The ripples on all the power
supply rails have significantly reduced, with the exception of the +100V rail.
Here the actual low frequency ripple seems to be in check at approximately
30mV P-P, but every second ripple peak exhibits damped high frequency ringing
at approximately 350 - 360kHz with 100mV P-P amplitude. I attached an image
showing the ripple and the ringing on the +100V rail.