problems with Dick Sniff's cheap 10Mhz CRO

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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.




Re: problems with Dick Sniff's cheap 10Mhz CRO



"Simple Simon"

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** No such problem exists on any examples I have seen or heard about.

  Focus and linearity are both very good.



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** ROTFL   !!!

I guess you are testing it with a fast rise and fall, lowish frequency
square wave.

I guess you have never used an analogue CRO before either.

One of the nice things about them is the ability to visually judge rise and
fall times from the brightness of the trace -  where it is simply invisible,
the times are *very* short.

Most digital CROs supply a false impression of slowness.


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**  Seems like you have one with a damaged / faulty CRT.


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 ** It is dead  Simple  -  Simon.



.......  Phil




Re: problems with Dick Sniff's cheap 10Mhz CRO


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.


3) Why can I not see the near vertical lines on a wave, but only the peaks
and troughs?






Re: problems with Dick Sniff's cheap 10Mhz CRO


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

Bob



Re: problems with Dick Sniff's cheap 10Mhz CRO



"Bob Parker"
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 **  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




Re: problems with Dick Sniff's cheap 10Mhz CRO



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Yup, this shows the issue (excuse the quality)

http://www.chrome64.org/CRO.jpg

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



Re: problems with Dick Sniff's cheap 10Mhz CRO



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

Re: problems with Dick Sniff's cheap 10Mhz CRO



"dmm"

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**  Nope.

  It just don't have one.

  Works fine,  however.




........  Phil





Re: problems with Dick Sniff's cheap 10Mhz CRO


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 http://members.ozemail.com.au/~bobpar/P9146256.JPG my what a
big picture 741Kb


wrote:

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



Re: problems with Dick Sniff's cheap 10Mhz CRO



"Simple Simon"
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**  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













Re: problems with Dick Sniff's cheap 10Mhz CRO


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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:
http://members.ozemail.com.au/~bobpar/P9146256.JPG
    I agree with Phil - the CRO's faulty so ask DSE for a replacement.

Bob



Re: problems with Dick Sniff's cheap 10Mhz CRO



"Bob Parker"


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 ** Your supplied probe has one  ????

 I know the one shown in the manual does.

 Only matters when set on 10:1 anyhow.




.........  Phil



Re: problems with Dick Sniff's cheap 10Mhz CRO


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    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

Re: problems with Dick Sniff's cheap 10Mhz CRO



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Mine has one, but its on the connector end not the probe itself like the
manual would suggest.



Re: problems with Dick Sniff's cheap 10Mhz CRO



"Simple Simon"
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**  No.

The DSE user manual has it shown on the BNC socket end,  fig 3.5,  page 9.

Geezus  -  there out to be a law against supplying anything technical to
this Simon boob.

Like the one the prohibited the sale of guns to Indians in the Old West
!!!!






........   Phil





Re: problems with Dick Sniff's cheap 10Mhz CRO


so what kind of camera did you have then



On 17/12/2006 16:00 Simon wrote:
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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:
http://members.ozemail.com.au/~bobpar/P9146256.JPG
    I agree with Phil - the CRO's faulty so ask DSE for a replacement.

Bob




Re: problems with Dick Sniff's cheap 10Mhz CRO


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    Not sure which camera you're referring to. You'll have to ask Simon
what he used. Mine was taken with an Olympus C-740.

Bob

Re: problems with Dick Sniff's cheap 10Mhz CRO




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No, thank you!

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I played with the compensation, but without a decent sine to adjust
against its a waste of time.

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thanks for the photo Bob, I adjusted my settings to match yours and I get
a solid flaring blob :)

Back she goes!


Re: problems with Dick Sniff's cheap 10Mhz CRO



"Simple Simon"

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




........    Phil




Re: problems with Dick Sniff's cheap 10Mhz CRO



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Could someone here please send Philthy Phil a Christmas present.
Make it a new vocabulary which doesn't include all the potty mouth stuff he
seems to have overdone here in the past year please.




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