problems with Dick Sniff's cheap 10Mhz CRO

what a surprise :)

Im a complete noob, so can anyone answer the following?

1) Why is the image wider at the bottom of the screen than at the top? 2) Why can I only focus one side of the screen at a time? 3) Why can I not see the near vertical lines on a wave, but only the peaks and troughs? 4) Why is the line wider on one side of the screen than the other? 5) Have I got a dud?

Its a real bitch to level the screen too, the mechanism at the back appears to be seized. I got there in the end though.

I suspect what you are tring to say is when I display a sinewave, why is it the trace almost disappears as it crosses the X Axis, while when it turns on the Y axis it is as clear as daylight.

A simple photo of what's on the screen would remove all doubt and speculation. Any chance of doing that, Simon?

Bob

"Bob Parker"

** Oh come on - the boob is looking at a fast square wave.

A possible alternative explanation for his alleged image distortion is the CRO is (or has been) placed on top of a speaker magnet and hence magnetising the steel case.

........ Phil

** Take the CRO bank - get another one.

The CRT is faulty.

........ Phil

An about face hey Phil? A few posts back you were accusing Simon of not knowing what he's doing. Now it's suddenly a different story. Hey, but is anyone here surprised? Nope.... just the little bleeding toaster boi doing ape shit as usual. :-(

There should be a variable capacitor near the probe end. Adjust it until you get nice vertical and horizontal lines on the signal.

"Simple Simon"

** The boob is using the " Probe Adjust " signal - which IS a 1 kHz SQUARE WAVE !!!!!!

There are MANY things wrong with the trace - it lacks width, is out of focus, has bad astig, has bad tilt on the wave tops and bottoms etc.

I guess that CRO it left the factory in China WITHOUT the internal trims being adjusted.

Take it back - Simon.

...... Phil

G'day Simon, Thanks for doing that. A picture's worth >1K words. :-) Apart from the fact that the probe's compensation is badly misadjusted, to me it looks like your CRO's showing the symptoms of excessive EHT (CRT high voltage supply) which is making the trace too small and wrecking the astigmatism (focus over the whole screen area). The probe adjustment signal should look like this photo:

I agree with Phil - the CRO's faulty so ask DSE for a replacement.

Bob

"dmm"

** Nope.

It just don't have one.

Works fine, however.

........ Phil

"Bob Parker"

** Your supplied probe has one ????

I know the one shown in the manual does.

Only matters when set on 10:1 anyhow.

......... Phil

"Simple Simon" = SS

** This mysterious Q is now explained.

SS ( who has no clue even what a sine or square wave is) has used the " Probe Adjust " signal to test his new toy. This is a fast 1kHz square wave of 0.5 V p-p.

The DSE produced " User's Manual " for the CRO shows a drawing ( on page

9 ) of what the trace should look like which is technically WRONG - the rises and falls are shown having the same width the top and bottom lines.

Arrrrrrrggggggghhhhhhhhhh !!!!

....... Phil

The previous owner of my Q1803 got a faulty probe with it. When he took the probe back to DSE under warranty, they supplied him with a better one which does have a compensation adjustment cap.

Bob

Thats exactly what Im saying :)

Yup, this shows the issue (excuse the quality)

Im a complete noob with a CRO btw, so excuse me if its something really dumb :D

by the way you put the probe tip on the oscilloscope tag marked PROBE ADJUSTMENT then you adjust the capacitor on the probe. you might have tweak the Y and X knobs to get a suitable display

see photo at

my what a big picture 741Kb

There should be a variable capacitor near the probe end. Adjust it until you get nice vertical and horizontal lines on the signal.

Man did I get that wrong! But a original description I had to work off "peaks and troughs" ? on a square wave I would of called them "highs and lows"

so what kind of camera did you have then

G'day Simon, Thanks for doing that. A picture's worth >1K words. :-) Apart from the fact that the probe's compensation is badly misadjusted, to me it looks like your CRO's showing the symptoms of excessive EHT (CRT high voltage supply) which is making the trace too small and wrecking the astigmatism (focus over the whole screen area). The probe adjustment signal should look like this photo:

I agree with Phil - the CRO's faulty so ask DSE for a replacement.

Bob

"Simple Simon"

** I wonder what this * monumental congenital f****it * imagines the word "square" means.

........ Phil