| Electronics > Beginners |
| Tektronix 2235 AN/USM-488 - trace stability issue |
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| F3nn3c:
Hello, forum members: I have acquired two Tektronix scopes a while ago, and finally decided to check a Tektronix 2235 AN/USM-488 in hopes to set it up as my bench scope. Good news - both A and B channels appear to be working, and trigger from an internal oscillator. Calibration also appears to be OK, the square wave follows the graticule markings both vertically and horizontally. Traces are rather bright and rather sharp, I can get them down to ~1mm in width. Bad news - trigger signal seems to be unstable. For no apparent reason trigger is being randomly lost, and the channel displays a baseline instead of a signal. Mostly happens on a B channel, but A is also affected. Also, both baselines when this happens are not clean, but rather rapidly pulsating/flickering both for A and B. After a couple of minutes the traces are back - stable and sharp... Does anyone have any suggestions/pointers as to where to look for a potential problem spot? Switches to clean? Transistors to reseat? Thank you, Dmitri |
| Jwillis:
I would start by giving all the pots and switches a good cleaning with some Deoxit .Make sure all the connections inside are seated well. Thats probably all it needs .Looks like as nice scope . |
| David Hess:
Your photograph is too out of focus to read some of the control settings. Make sure P-P Auto is pushed in. Do not use the VERT MODE trigger source with ALT vertical mode; this is a special triggering mode only appropriate for overlapping signals. Instead use CH1 or CH2 trigger source or the external trigger source with another probe connected. |
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