RCA Oscilloscope

This is an RCA WO-33A oscilliscope, from about 1960. Here's the manual (PDF), complete with a schematic.

The oscilliscope from above with its case removed.

A closeup of two tubes. They are branded RCA. The printed circuit board has the RCA logo and reads "Oscilliscope WO-33A C-907097."

This isn't a very capable scope—it claims to be good to 4 MHz, although the internal sweep oscillator only goes to 75 KHz (or "KC," kilocycles, according to the front panel!). A view of the CRT mounted in the scope.

The probe is not very capable either: one clip is for ground, one clip is 1×, and the other is 10×. The leads are very short.

The oscilliscope probe as depicted in the original product manual. The caption reads, "Figure 1. WG-349A direct/low-capacitance probe and cable supplied with WO-33A"

The only problem with the scope was the high voltage filter cap—the big paper one in the picture below. It was leaky, both physically and electrically... it was oozing wax out the bottom and the CRT wouldn't focus.

A view from beneath the scope.

I found a suitable (and free!) replacement cap inside an old microwave. The replacement (0.86 μF, 2000 V) is much larger than the original, so I had to install it in a different location. It's the thing wrapped in electrical tape, below.

The scope in operation, displaying a sine wave.