Hi Bill,
ripple? ?your on the right track I believe.
try checking the ripple output on all the power supplies. ?the caps in these older scopes go bad with age and the first sign is ripple on the DC supplies.
recapping the main electrolytics involved in the power supplies usually cures.
?jim
On Jul 10, 2012, at 2:38 AM, maninashed1 wrote:
?
Hi,
I have a Tek 468 analogue with digital display and storage. The problem: the scope works fine in analogue mode, however when digital mode is selected, the trace appears to be modulated at a higher frequency causing a blurred display. If the timebase x10 is used to expand the trace, it appears to be composed of a semi sinusoidal waveform.(Its not possible to determine the frequency as in the digital mode the timebase control doesnt seem to have much effect)and its not possible to re-create this effect in analogue mode. I have checked grounding connections, re-seated the i/cs etc all to no effect. My next step is to check the digital psu for excess ripple.
Has anyone come across this problem before or can anyone point me in the right direction?
Note: The digital functions seem to work ok,save, store etc.
Very often the 'scope will not 'POST (power on self test,) but will come on in analogue mode.
The digital LED display does work, and so do the cursors and they do measure, but the cursors are modulated in the same way as the trace.
Bill
