Building My Own Oscilloscope

[Miguel López]

Is it possible to make a high voltage capacitor, using a double-sided PCB? How much capacity would be achieved (pF/cm2)?

Had anybody try this before?

[pwdrive]

If the board thickness is 1.6mm (typical thickness) and the dielectric constant is 4 (typical) then the capacitance = 2.2pf per square cm. (approx)
Not sure of the voltage rating.

Lawrence.

[Miguel López]

I finally did it!!!!

The scope is working OK with the 60Hz EHT PSU. I got -1300V for cathode and +3500V for anode, on the CRT. No noise present. See pictures bellow. It istill a bit unfocussed but i guess this due to some lack of negative voltage in the focussing plates. I hope to solve that next weekend. Synchonization is perfect, and the trace is steady in the screen.

[boiss]

Great stuff Miguel,
Keep up the enthusiasm.
Mike

[Miguel López]

This is the oscillogram of a TTL signal. The upper level shows a peak that is not present in the original signal. Any idea on how to solve this ?

[Miguel López]

I solved the problem with the peaks. Silly me.

The S51 Y-amplifier has two coils (inductors) in series with the anode resistors, in the diferential amplifier. I connected the deflecting plates between the resistor and the coil (erroneously), and there were the peaks. Now I have corrected that, connecting the plates to the anodes of the diferential amplifier and the square signal looks great.

Yesterday I also finnally supressed the flyback trace by adding an RC network plus a diode, in the grid of the CRT, taking the blanking signal from the screen of the 6BW7 in the time base. It worked fine. I will show oscillograms soon. I'm also drawing all the schematic in an old software (MS-DOS based), to make some kind of manual when finished.

Now I will begin to adjust ranges.

[Skywave]

Miguel, you are clearly making excellent progress with this project. I've been 'doing electronics' - as a hobby and for a living - for over fifty years now and I don't think I could have achieved the success - and provided the determination to succeed - that you have obtained and shown: well done!

Incidentally, what is the MS-DOS based software that you will use for your schematics?

Al. / June 4, 2013. //

[pwdrive]

Same from me Miguel, you are doing an excellent job with the resources you have.

Lawrence.

[Miguel López]

Thanks for you kind words.

I'm using OrCAD v3.21 from 1988. It works great!!!.

[AlanBeckett]

That takes me back a long way. Unfortunately I changed jobs and the new Comany used a different Package.

Alan