problems with Dick Sniff's cheap 10Mhz CRO

[Phil Allison]

"Simple Simon"

Im a complete boob, 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?

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

Focus and linearity are both very good.

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

** 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.

4) Why is the line wider on one side of the screen than the other?
5) Have I got a dud?

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

Its a real bitch to level the screen too,

** It is dead Simple - Simon.



........ Phil

 

[Simon]

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.

 

[Bob Parker]

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?

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

Bob

 

[Phil Allison]

"Bob Parker"

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

** 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

 

[Alan Rutlidge]

"Simon"



** 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. :-(

 

[dmm]

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

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

 

[Phil Allison]

"Alan Cuntlidge"

An about face hey Phil?

** Try reading my first reply again - **** .

You must be blind as a dead bat.




........ Phil

 

[Phil Allison]

"Simple Simon"

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

** 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

 

[Bob Parker]

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

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

 

[Phil Allison]

"dmm"

There should be a variable capacitor near the probe end.

** Nope.

It just don't have one.

Works fine, however.




......... Phil

 

[Phil Allison]

"Bob Parker"

Apart from the fact that the probe's compensation is badly misadjusted,

** Your supplied probe has one ????

I know the one shown in the manual does.

Only matters when set on 10:1 anyhow.




.......... Phil

 

[Phil Allison]

"Simple Simon" = SS

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


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

** 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

 

[Bob Parker]

"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

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

 

[Simon]

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.

Thats exactly what Im saying

 

[Simon]

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

Bob

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

 

[Alan Rutlidge]

"Alan Cuntlidge"




** Try reading my first reply again - **** .

You must be blind as a dead bat.




....... Phil

Oh deary me. They must have to call him "each way bet Phil".
Yes, I did read your initial response. You were quick to have a go a Simon.

You can tell Toaster Boi has lost the debate as well as the plot.
Resorting to 4 letter words which regrettably make up the most of his
limited vocabulary.
You're a sad little old man with no friends.

 

[Phil Allison]

"Alan Cuntlidge"



** Try reading my first reply again - CUNTHEAD .

You must be blind as a dead bat and dumb as a dead donkey.






........ Phil

 

[Phil Allison]

"Simple Simon"

" Im a complete boob with a CRO btw,"

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

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




......... Phil

 

[Simon]

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. :-(

heh, Ive actually got Phil blacklisted, so there ya go.

So the concensus is that its busted?

 

[Alan Rutlidge]

heh, Ive actually got Phil blacklisted, so there ya go.

So the concensus is that its busted?

Hi Simon,

From what you have described, it sounds to me it is faulty. Get it
exchanged for a new one.

Cheers,
Alan