Does anyone have a cheap electrostatic CRT?

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Re: Does anyone have a cheap electrostatic CRT?

Post by Admin on Tue May 30, 2017 6:05 pm

Hi Ivan,
Thank you very much for the information and the kind offer. As you stated, the tube is quite large for me so it is not really what I can use. But when I followed the link you gave on E-Bay there were also several other electrostatic tubes. This one spoke tome - it said "Buy Me". I bought it.

http://www.ebay.co.uk/itm/RARE-CRT-vintage-oscilloscope-cathode-ray-tube-6LO1I-NOS/111974247715?_trksid=p2047675.c100623.m-1&_trkparms=aid%3D2220072%26algo%3DSIC.MBE%26ao%3D2%26asc%3D44293%26meid%3D026ab461f3314401bb430cd1e2cb035d%26pid%3D100623%26rk%3D1%26rkt%3D6%26mehot%3Dag%26sd%3D371959826741

It is a 1200 V tube, 43mm x 53mm square. It is also quite short :-) A little bigger than I had wanted, but it should do the job well.

I am now planning the chassis, PSU and the driving circuits. Thank you very much, once gain you have helped me tremendously.

Tomorrow I will order the 1M pots for the focus and brilliance. If I run the cathode at -1200 V then the deflection plates can be around 0v ground and I can use a 1/2-decent wideband transistor amplifier to drive the deflection. At least that is the thought. Just need to get a basic tube working then see what deflection signals I need.

Thank you once again. Very best regards from Harry - SM0VPO

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Re: Does anyone have a cheap electrostatic CRT?

Post by Ivan on Tue May 30, 2017 5:38 am

Hi Harry,
I have one of the DSO nano line for several years and it works fine. Maybe you missed the AC/DC coupling selector somewhere in the menus?
Did you try to search for "CRT oscilloscope" on ebay.co.uk? Maybe I have this one http://www.ebay.co.uk/itm/8LO39V-8-39-Russian-Oscilloscope-8cm-3-BLUE-color-Small-Flat-CRT-Tube-NEW-/371959826741?hash=item569a888935:g:IB8AAOSwJb9Ws9kX or similar even in my surplus. I can look for it, but I am really afraid of breaking the tube during posting it. Rolling Eyes And it is bigger than that you are searching (8 cm dia).
The chinese kit looks cute, too. But the total bandwidth 200 kHz is not much.

VBR from Ivan

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Re: Does anyone have a cheap electrostatic CRT?

Post by Admin on Mon May 29, 2017 4:09 pm

Hello Ivan,
Thank you very much for the information. I have bought one of those:

https://www.aliexpress.com/item/New-Style-Mini-DSO211-Nano-ARM-Pocket-Size-Portable-Handheld-LCD-Screen-Digital-Storage-Oscilloscope-8MB/32813767411.html?spm=2114.01020208.3.2.I2KGzc&ws_ab_test=searchweb0_0,searchweb201602_5_10152_10065_10151_10068_10136_10137_10157_10060_10138_10155_10062_10156_437_10154_10056_10055_10054_10059_303_100031_10099_10103_10102_10096_10147_10052_10053_10142_10107_10050_10051_10171_10084_10083_10080_10082_10081_10110_519_10111_10112_10113_10114_10182_10185_10078_10079_10073_10123_142,searchweb201603_2,ppcSwitch_5_ppcChannel&btsid=9e09086e-5f30-4ba7-8869-aafacba20216&algo_expid=139536cf-f50d-4c30-bf6b-2f44c0712302-0&algo_pvid=139536cf-f50d-4c30-bf6b-2f44c0712302

And to be honest it is very strange to use. As you wrote, it is ok for audio use, providing there is no DC component, but I think I have an earlier model. When I switch it ON there is always a demo display, and any DC component just pushes the display off the screen. Perhaps I need to update the FW.

I was thinking about building something like this:

http://www.learningelectronics.net/circuits/minimalist-oscilloscope.html

But I would use -300v (perhaps a little more) on the cathode so that the deflection plates are at or around ground potential - no need for capacitors to isolate the +300v. That would get me started. Then update with simethink like this to get more gain, sync, and so-on:

http://www.antiqueradios.com/forums/download/file.php?id=73698&sid=6994cbc64a72ee49eb6c421f79b535b7

I already have the tubes themselves, but just need an electrostatic CRT. I was thinking about a case that was only 4cm to 6cm high so that it could be stacked on the bench with other items, such as PSU and a HB DDS generator. I have already built the DDS generator prototype: just need a PSU and boxing.

Thank you very much for your reply. I do appreciate your input. Have you tried on of those China scopes for yourself?
The menu is also a bit primitive and you have to use it daily to remember the 2-letter abbreviations. The manual is also a bit cryptic. But it works for low voltage at LF.

Very best regards from Harry - SM0VPO

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Re: Does anyone have a cheap electrostatic CRT?

Post by Ivan on Mon May 29, 2017 1:37 pm

Hi Harry,
it is obvious that you want to make a scope by yourself. BUT - did you ever consider something like this?
https://www.seeedstudio.com/DSO-Nano-v3-p-1358.html
https://www.aliexpress.com/premium/nano-pocket-size.html?ltype=wholesale&d=y&origin=y&isViewCP=y&spm=2114.01020208.8.4.y0wKYc&initiative_id=QRW_20170529063535&SearchText=nano+pocket+size&productId=32813767411&blanktest=0&tc=ppc
It has a size and weight of a mobile phone and is OK for AF use.

VBR from Ivan

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Does anyone have a cheap electrostatic CRT?

Post by Admin on Sun May 28, 2017 9:15 pm

When I sold the house in Lunda I had to downsize a lot. This meant getting rid of the shack-heater oscilloscope, Maccaroni 995 signal generator, spectrum analyser, and loads of other goodies. But I really miss the oscilloscope.

My thought was to build myself a very simple oscilloscope, so I am seeking a cheap electrostatic tube, around 1" or 2", round or square. If you have one on the shelf gathering dust and you want to part with it then please let me have the opportunity to buy it. If it is an oddball or special tube then tube data would be appreciated.

I was thinking about a battery-powered oscilloscope using my inverter project to get 1000v or so for the tube.

I will publish the finished scope(s) on HHH as the project developes.

Very best regards from Harry - SM0VPO


Last edited by Admin on Sun May 28, 2017 9:18 pm; edited 1 time in total (Reason for editing : seemed like a good idea at the time.)

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