Re: Low spec 'scope.

On a sunny day (Wed, 28 Aug 2024 13:41:10 +0100) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1qz05im.msb64xeltdhmN%liz@poppyrecords.invalid.invalid>:

Jan Panteltje <alien@comet.invalid> wrote:
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On a sunny day (Wed, 28 Aug 2024 08:39:25 +0100) it happened
liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
<1qyzrl3.ocj6lm4e4yaN%liz@poppyrecords.invalid.invalid>:
 

The recent thread on high-end oscilloscopes has reminded me of a project
that I shelved some years ago and might be due for resurrection:  I am
looking for a real-time display about 3" x 4" that can behave as an X-Y
oscilloscope with a bandwidth of about 100 Kc/s; a flat panel would be
ideal.
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Currently I am using an actual X-Y oscillocsope to monitor the output
from a stereo gramophone cartridge, which allows me to check historic
discs for damage or faulty recording geometry.  The tube is about 14"
long, which means it has to be a standalone shelf unit and I can't build
anything like it into portable equipment.
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I've not come across anything like this, but I'm sure such things either
exist or can be made by adapting something that is readily available.  I
have never been down the digital route, so anything that would need a lot
of programming from scratch will never get built.

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This was an experiment:
 https://panteltje.nl/panteltje/pic/scope_pic/
works for audio, has spectral display too,
can also send screendump as text file to Usenet.
Control via RS232 or some buttons if you can code.

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Thanks very much for that.  It has most of the reatures I need and the
sampling rate is just about adequate.  It 'remembers' its last settings,
which is essential for this application.
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I have coded in the past but it was a most frustrating exercise and
something I would like to avoid if possible.  Also, I don't have any way
of connecting to the chip and uploading the code.
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Cost? Maybe the LCD is the most expensive part, 5 dollars?

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Very reasonable
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Display has low resolution, so I did a shift right a couple of times to
divide the output. A better display will give better resolution.

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The detail is extemenly important in this application - the minimum
resolution being 200 dpi.
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There are plenty of single chip cheap digital scopes on ebay.
 https://www.ebay.nl/itm/315279795435
  have not tried that one :-)

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I'll have to work through them and see which ones can be used as X-Y
scopes, with good enough resolution and the ability to start fully
functional from power-up.
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Failing that, I have an oscilloscope tube and driver chassis, so I could
mount it horizontally in the bottom of the box with a 45-degree mirror,
so I can look down on it through a hole in the horizontal control panel.

I have designed and build several scopes with CRTs in the past,
first one used a DG7-32 CRT:
 https://www.radiomuseum.org/tubes/tube_dg7-32.html
Actually the first one was an old TV CRT, much bigger, with magnetic deflection and a car ignition coil as HV generator
connected to the output of an audio amp with EL84, I made the amp oscillate at a few kHz (feedback to input) to drive that ignition coil.
stereo tube amp for H and V.
It is simple to make some 500V HV for for example a small CRT or GM tube:
 https://panteltje.nl/panteltje/pic/gm_pic/
this one uses a  simple 10:1 audio trasformer in reverse as flyback step-up:
 https://panteltje.nl/panteltje/pic/gm_pic2/
Microchip PICs are great, have build in PWM generator, ADCs, EEPROM, voltage reference, what not.

The fasted analog scope I build was 300 MHz with an East German CRT, circuit was from Tek.
Transistor amplifers for deflection with BFY95 IIRC.

I still use my old Trio analog scope up until these days, works up to about 20 MHz (10 MHz officially).
for anything more RF I use RTL_SDR sticks and the spectrum analyzer I wrote:
 https://panteltje.nl/panteltje/xpsa/index.html

If you have analog video and an x,y scope with intensity input:
 https://panteltje.nl/panteltje/scope_tv/index.html
TV!