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Old 29th Sep 2019, 8:53 am   #1
M3VUV51
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Default Is my scope stuffed?

been trying to look at a 20mhz sinewave today on my tec 453,i get these (see pics),thats on .1us div timebase settings,does it look normal?,looks like i have timebase issues,that was on manual and auto trigger,both look the same.,im getting dozens of peak to peak per div,not 4 or so.
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Old 29th Sep 2019, 9:53 am   #2
high_vacuum_house
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Default Is my scope stuffed?

Good morning,
Start by looking at a low frequency sine wave such as 1Khz and see if it looks correct. Trying to resolve a 20Mhz sine wave may be pushing the oscilloscope’s Y amplifier a bit too much. If a 1Khz sinewave looks good then increase the frequency in stages to see if the performance rolls off gradually or fails at one point. Also check the oscilloscope probe as these can cause issues. Can the signal generator produce a nice sinewave at these frequencies. It might be generating some harmonics which is interfering with the desired frequency .

Christopher Capener
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Old 29th Sep 2019, 10:18 am   #3
M3VUV51
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Default Re: is my scope stuffed?

I sorted it the tb knob was in the wrong position on the shaft,i now see about 3 waveform peaks per div at .1us tb,at least i think its .1 but could be one as its a job to see as the dial plastic has yellowed with age,waiting on a replacement nos to arrive from the usa.,cheers Paul m3vuv
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Old 29th Sep 2019, 10:31 am   #4
M3VUV51
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Default Re: is my scope stuffed?

this is what i see now,its at .1us div i think and 20mhz.
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Old 29th Sep 2019, 11:50 am   #5
Herald1360
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Default Re: is my scope stuffed?

That looks credible. For 20MHz anyway though not 20mHz (0.02Hz).

Can't you confirm whether the setting is .1uS / div by extrapolation from a legible or at least known setting? Even if you have to count round from 1mS / div as confirmed by a 1kHz sinewave input it's not that onerous.
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Old 29th Sep 2019, 4:13 pm   #6
RogerEvans
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Default Re: is my scope stuffed?

Take care when you swap the new knob into position. The white spot on the knob relates to the B timebase and the two lines on the transparent skirt relate to the A timebase. When you remove the black knob the skirt will stay in place and you need to release another pair of grub screws to remove the skirt. If the two timebases are locked together before you remove the parts then don't move either shaft before replacing the knobs and make sure the knobs are locked when you replace them. I didn't do this and had 'fun' trying to get them back in the correct sync after moving the shafts for easier access to the grub screws.

As Herald 1360 says you can always use the 1kHz calibrator signal to find the 1msec/div setting and count from there.

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Old 30th Sep 2019, 4:30 pm   #7
John_BS
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Default Re: Is my scope stuffed?

I'll second what Roger has stated: put the timebase into a known position before removing the knobs, and carefully replace in the same! Also (and counter-intuitively) the timebase knobs have 0.050" hex grub-screws, whereas all the smaller knobs on this scope are 0.0625"

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Old 1st Oct 2019, 10:44 pm   #8
flyingtech55
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Default Re: Is my scope stuffed?

"Is my scope stuffed?"

No.


HTH

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Old 2nd Oct 2019, 9:44 am   #9
Oldmadham
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Default Re: Is my scope stuffed?

Yep! Just as in the OP's "carbon copy" posting over on EEvblog!
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Old 4th Oct 2019, 11:53 am   #10
M3VUV51
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Default Re: Is my scope stuffed?

yup it was on eev blog as well,more irons in the fire the better i think!,anyway,got the new tb clear skirt arived and fitted,its a new old stock tek part in the original tek box with part numbers etc,seems it was a lucky find on ebay!,my scope was made in 65,postage was 3x the cost of the dial/knob tho but woth it in my opinion,pic attached.
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