I was trying to repair my tek 2236 and was in need of measuring a -2kV line, only problem: my best Multimeter can only do 1000 V so I had to yank up 30 3k3 Ohm resistors in series to make a 100M Ohm Resistor. All put into some trash plastic tube makes a usable series resistor for the MM.
Be sure to watch the safety advice and keep your hands off the circuit under test!
So currently I’m testing several different approaches on generating the HV for the scope project. This is my favourite for it’s simplicity. The schematic is Here:
Be sure to use a very good cap, that can withstand the hight currents when discharging. The parts are not critical, any transistor, that can handle the power will do and the resistor values are just for orientation.
Have fun watching!
The whole arrangement will make a top voltage of about 400 V with two secodaries at 24 V, you can go muuuuuuuch higher with lower values and resistor values. In my very first tesla-coil almost the same arrangement makes somewhat 4 KV.
Good ideas not always turn out for the best but have some value anyway.
The two trafos you see are way to “soft” and at 200 mA the output will drop from 220 VAC to 210 already.
Nevertheless it works fine until that and I will just have to wait and see if some better trafos find me.
I just made up some working test setup for the homebrew oscilloscope project and the screen came to life for the first time:
Here is my setup:
By the way is the 3KP1 / DG 7-113 with the green p1 phosphor. If you ever come across the white phosphor (3kp4) you found some nice piece of rareness. The P4 version was used in the Pilot TV-37, one of the first portable TV-sets. Check out David and Marlene McClellans blog about restoring one! Also check out some video of it here.
Hi, I just started a dream project: Building an oscilloscope from scratch. Originally I wanted to use a russian 13LO37I but it turend out to be too bulky so I went and scored a waaay smaller 3KP1 / DG 7-113 from ebay.
I’ll put up a high res Photo of the tubes weiring system at my website.
My last video reminded me of one of my very first high Voltage Projects. It is a Push-Pull high Voltage converter, that is made out of an old flyback transformer from a black & white TV-set, 2 2n3055 Transistors, 2 resistors,1 cap and a bunch of wires. It performs very well and reliable .
Okay I’ve been working on this for a year now but I can see the end and hope I get it done in a month or so.
Sorry Mighty Ohm The geiger shield had to take a step back before high voltage and vintage tube stuff.
Until I can make the vid you can enjoy these pics of the build:
I had the need to test some transformers and didn’t like the idea of dealing with blank line voltages. The solution was a protective circuit with two relays closing their contacts only, when an acryllic case is closed.
I ordered a russian scope tube some weeks ago but it didn’t arrive yet. Yesterday I thougt, I could use something like 4kV to test the thing when it finally arrives. I looked through my options and ended up with a NE555 solution. And when I yanked up a schematic today I listened to the Amp Hour where they were talking about their 555-contest to be ending on march 1st so I figured to speed my project up and make an entry:
Here’s a little vid first:
Unfortunately I had do divert from my original Idea of using a 2n3055 transistor – the tractor under the transistors – because i didnt think of the necassery driving power so I had to use some modern day FET.
Lets have a look on the Waveform:
first is the 555s output after the protection restistor
here the FET drivers output:
still nice looking
at the driver-FET:
starting to look messy
and the transformer connector:
The funny thing was, that at some point, that I unforunately didn’t capture the last waveform changed into 3 perfect sine waves on top of each other. Does anyone have an idea what that coult have been? And it still works – strange.