The purpose of this posting is to share my wonder and excitement of doing something new and challenging in electronics (I still consider myself a noob).
I built a test jig for (half of a) 12AX7 vacuum tube. The 12AX7 is one of the most popular small-signal amplifier tubes. The 12AX7 contains two amplifiers, but I only used one of them. I have been looking at tube testers for a while but I want full power testing and I want to see the input and outputs on my scope. I decided to build my own jig to see a 12AX7 working.
I used the noval breakout board from Electro-Resales (1,2) (no relation, just a happy customer). In order to build my jig I used the info on the 12AX7 datasheet from General Electric (3). I took reasonable care to not short anything and double-checked my build before giving it some juice. I was super jazzed when I saw a big sine wave coming out of this thing. I am grateful to the many smart, hard-working son-of-a-guns that invented and refined vacuum tubes.
I inverted the (duplicated) input signal on the scope for ease of comparison. Both channels of the signal generator are outputting same signal and are sync'ed. Of course the amplifier is inverting.
Input signal (blue, scope channel 2) is 1kHz sine @ 3.0V P-P and output signal is (inverted) 180V P-P. Does this mean the voltage gain of my amplifier is -60 V/V?
I notice that as I crank up the input to 4.0V P-P, the top of the output waveform is distorted. I want to bias the input so that I can even that out. I know that's very easy to do, but I've got to hit the books. This is how I enjoy learning: practical problems sitting on the bench in front of me.
I also realized that I need a couple more cables, adapters, and doodads.
What fun!
(1)
https://www.electroresales.com(2)
https://www.ebay.com/str/electroresales(3)
https://frank.pocnet.net/sheets/093/1/12AX7A.pdfEDIT:
I used a Micsig DP10013 high-voltage differential probe in X500 mode to get the tube output to my scope.