is my scope  buggered? - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: September 29, 2019, 07:11:28 am
content: got this on my scope today trying to look at a 20mhz sinewave the timebase knob was fully clockwise(should be .1us,is what im seeing normal?

author: ataradov
author_rank: Super Contributor
timestamp: September 29, 2019, 07:27:01 am
content: Looks like it is jut not properly triggered. Although you could make better pictures.And there is no need to create multiple topics for the same issue.

author: m3vuv
author_rank: Super Contributor
timestamp: September 29, 2019, 07:30:42 am
content: it was triggered fine,took the pic on my phone,i will dig my camera out.

author: ataradov
author_rank: Super Contributor
timestamp: September 29, 2019, 07:32:42 am
content: How do you know if it does not properly show nay signal? Have it been stable before? Have you tried to adjust the trigger level?

author: m3vuv
author_rank: Super Contributor
timestamp: September 29, 2019, 07:41:11 am
content: hope thats better,its the best pic i can get.

author: m3vuv
author_rank: Super Contributor
timestamp: September 29, 2019, 07:45:02 am
content: that was on auto trigger,ive tried it on manual trigger too,if i adjust the trigger wrong the trace dissapears.

author: ataradov
author_rank: Super Contributor
timestamp: September 29, 2019, 07:47:06 am
content: Can you make a clear picture of all the controls on the scope? There are many settings that can cause this behavior.Also, have you tried with lower frequencies?

author: m3vuv
author_rank: Super Contributor
timestamp: September 29, 2019, 07:58:52 am
content: the settings are 50mv div,ac coupled,see pic,seems fine until about 100khz then goes imposible to view properly.may have to rotate the pic.

author: m3vuv
author_rank: Super Contributor
timestamp: September 29, 2019, 08:01:35 am
content: just noticed the x10 was on turning it off just makes the display brighter but doesent alter the trace.

author: tggzzz
author_rank: Super Contributor
timestamp: September 29, 2019, 08:09:14 am
content: The answer is in your other thread on this topic.https://www.eevblog.com/forum/beginners/looking-at-a-waveform-on-a-scope/msg2714180/#msg2714180If you can't manage to get a picture the right way up, I suspect you will find it difficult to get the scope controls in the right positions.

author: ataradov
author_rank: Super Contributor
timestamp: September 29, 2019, 08:10:50 am
content: From what I see you have 10 or 5 us/div set. It is not very clear from the picture, but 0.1 us/div setting is close to the bottom of the dial.

author: maginnovision
author_rank: Super Contributor
timestamp: September 29, 2019, 08:12:35 am
content: Can you push the center of time/div knob in and make sure time base is correct for frequency? Norm trig is good, level can be 0 if it's a sine wave. Some controls may be dicky so wiggle and turn a bit too.

author: m3vuv
author_rank: Super Contributor
timestamp: September 29, 2019, 08:42:23 am
content: the time div center knob is locked with the outer knob its all the way to the right,ie clockwise as far as it will go it should be 1us,although the knob is in bad shape,im waiting for a new one to arrive from the usa nos,heres a pic of my dso with the same settings, the signal is 20mhz modulated at 600hz,both scopes are in the pics with the same signal.

author: maginnovision
author_rank: Super Contributor
timestamp: September 29, 2019, 08:47:30 am
content: You can't do any better than 1us? Can you knock it down to about 1MHz and strike the modulation? The signal is definitely there. Also how is your PC scope at 1ms/div(I'm assuming it's/div) which makes a 1kHz signal and it's the same signal?

author: m3vuv
author_rank: Super Contributor
timestamp: September 29, 2019, 09:08:45 am
content: i think ive sorted it,looks like the knob was positioned on the shaft wrong,at 20mhz now i see about 3 waveform peaks per div on either 1 or .1 tb settings,i cant see the dial very well as the plastic is yellow with age,anyway with it fully cw,does that seem about right now?,cheers Paul m3vuv.

author: maginnovision
author_rank: Super Contributor
timestamp: September 29, 2019, 09:11:24 am
content: Picture?

author: m3vuv
author_rank: Super Contributor
timestamp: September 29, 2019, 09:28:02 am
content: this is a 20mhz signal,no modulation at 20mv div and .1 i think or could be 1 us div horiz.

author: ataradov
author_rank: Super Contributor
timestamp: September 29, 2019, 09:29:44 am
content: There are exactly two periods per division. This is correct.

author: m3vuv
author_rank: Super Contributor
timestamp: September 29, 2019, 09:33:10 am
content: great,thanks for your help,have a good weekend,73 paul m3vuv.