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Scope waveform slanted to one side. HELP.

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diy didi

Member
Hi all.
I have this scope for a while now. Works fine, except the waveform is slanted to the right as in the picture below.
I have tried adjusting some of the trimpots inside.....still nothing.
Trace rotation adjustment also doesn't help. Any ideas??
It is a 20Mhz GW Gos-623 scope. Can't find service manual either.
 

cowboybob

Well-Known Member
Most Helpful Member
Looks like the CRT may be rotated slightly off center. Graticule mask doesn't look square, either. Hard to tell.

What's it look like with a calibration square wave?
 
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ronsimpson

Well-Known Member
Most Helpful Member
I think you are showing the 'fall time' is faster than the 'rise time'. I do not know if that is your scope or the waveform.
What's it look like with a calibration square wave?
What frequency do you show? Try faster or slower.
 

unclejed613

Well-Known Member
Most Helpful Member
what are you feeding the signal from? what frequency? often function generators do the same thing near their frequency limit. it's a distorted sine wave as if it's being generated by a function generator with the symmetry control off center or out of trim.
 

electro_pa

New Member
Hi diy didi,
I worked as Tektronix Australia P/L service tech for years, and know analogue CRO's inside out!
Your display looks like timebase sawtooth is being modulated by your sine-wave display signal!
GW is a chinese product. Consider it may be suspect to contain dud electros, in power supply areas. Chinese electros are all suspect particularly from 1997 to 2007.
See this,http://en.wikipedia.org/wiki/Capacitor_plague
I suggest look for dud decoupling caps in your vertical amplifier's power supply circuits or any that are common to horizontal and vertical amplifiers and time-base generator.
Try jumping a good cap across any suspects, while you watch.
Try operating it as a X/Y display (time-base off), and check if vertical signal gives sloped line. Change sine frequency from very slow Hz to a MegaHz or so. Might give you a clue if slope changes.
Regards,
Clive.
 
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