My first job was at a TV/Radio shop before I was even in high school. I worked after school and on Saturdays, started at $1.25 an hour. In the right side window display was an Oscilloscope my boss had built in the 1930's. He gave it to me one day.
1930's Oscilloscope
My first job was at a TV/Radio shop before I was even in high school. I worked after school and on Saturdays, started at $1.25 an hour. In the right side window display was an Oscilloscope my boss had built in the 1930's. He gave it to me one day.
Here it is.
This is a very early RCA 906 CRT. There is no coating inside the glass so you can see the electron gun and deflection plates clearly.
Closeup of the CRT.
Under the chassis.
He did a nice job with the paint and lettering.
First thing, the power cord is... rough.
I replaced the power supply electrolytics, put it on the variac and it's doing something.
Using a scope to fix a scope. This is the horizonal sweep, it should be a nice clean linear sawtooth wave.
I had to disassemble, clean and lube all the potentiometers.
Pots reinstalled. The original wiring is rather crispy.
Now the dot is nearly focused.
The HV needed more filtering, there was still a little line frequency on the deflection plates. Looks like a nice dot now.
The horizontal sweep was still low and distorted. I found a bad plate resistor, the plate was only getting about 20 volts on it. This is the grid, and plate of the horizontal amp tube.
Replaced a few coupling caps, and found a bad resistor, now the sweep is looking a lot better.
It's an oscilloscope again!
(note: the green trace on the clear glass is just a reflection, you can't see the electron beam)
I found the book this scope was built from! Down to the diamond-shaped CRT support and everything. Radio-Craft Library No. 20 "The Cathode-Ray Oscilloscope by Charles Sicuranza, 1938.