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The RCA 151 oscilloscope was a cost-reduced scope made in 1936. While still expensive, this scope brought visual trace confirmation in the price range of the experimenter and small radio shop. This cost $47.50 in 1936, which is roughly $960 today.

This unit was built in Montreal, Canada, and was designed to operate on 25Hz power. This simply means it had a bigger filter in the power supply to compensate for the ripple from the lower frequency. It operates fine on modern US 60Hz power.

Tube lineup is a type 80 for the rectifier, a type 885 for the sweep, and two 6C6 that handle the remaining functions. The CRT is a 1" 913 tube. The 80 and 6C6 are fairly common today, the others are scarce or unobtainable.

This particular example is fairly pristine save for the "oops, it was live" mark on the right side near the input jacks. The inside appears to have been worked on at some point in the distant past, probably before WWII. I didn't open it because I need to clear another project off my actual test bench before doing so, but there are plenty of examples of the inner works online.

Here's the original ad for the scope (not mine) http://www.myvintagetv.com/oscilloscopes/rca_151_adv.jpg The inside (again, not mine) http://www.myvintagetv.com/oscilloscopes/rca_151_inside.JPG

The RCA 151 oscilloscope was a cost-reduced scope made in 1936. While still expensive, this scope brought visual trace confirmation in the price range of the experimenter and small radio shop. This cost $47.50 in 1936, which is roughly $960 today. This unit was built in Montreal, Canada, and was designed to operate on 25Hz power. This simply means it had a bigger filter in the power supply to compensate for the ripple from the lower frequency. It operates fine on modern US 60Hz power. Tube lineup is a type 80 for the rectifier, a type 885 for the sweep, and two 6C6 that handle the remaining functions. The CRT is a 1" 913 tube. The 80 and 6C6 are fairly common today, the others are scarce or unobtainable. This particular example is fairly pristine save for the "oops, it was live" mark on the right side near the input jacks. The inside appears to have been worked on at some point in the distant past, probably before WWII. I didn't open it because I need to clear another project off my actual test bench before doing so, but there are plenty of examples of the inner works online. Here's the original ad for the scope (not mine) http://www.myvintagetv.com/oscilloscopes/rca_151_adv.jpg The inside (again, not mine) http://www.myvintagetv.com/oscilloscopes/rca_151_inside.JPG

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[–] [deleted] • 1 pt

She's beautiful, and works!

This unit was built in Montreal, Canada, and was designed to operate on 25Hz power.

Never seen 25Hz on anything before, so I had to go look it up:

The first generators at the Niagara Falls project, built by Westinghouse in 1895, were 25 Hz, because the turbine speed had already been set before alternating current power transmission had been definitively selected. Westinghouse would have selected a low frequency of 30 Hz to drive motor loads, but the turbines for the project had already been specified at 250 RPM. The machines could have been made to deliver 16+2⁄3 Hz power suitable for heavy commutator-type motors, but the Westinghouse company objected that this would be undesirable for lighting and suggested 33+1⁄3 Hz. Eventually a compromise of 25 Hz, with 12-pole 250 RPM generators, was chosen. 20 MHz type deal. Looks like it belongs on an old submarine. Still use it from time to time, only adjustment it needs is a little "twist" on the trace usually. It was with this scope I learned the actual topology of the house electrical wiring... POOF and a probe goes flying across the room. Luckily that boneheaded move didn't break anything, but the important thing is I learned something that day.

Thanks again for posting some of the best content here.

[–] • 1 pt

I enjoy sharing the junk I pick up.

Leader made some respectable equipment in the day. The vocational school I attended in the 80s had 10MHz Leader scopes, they withstood years of abuse by high school kids.

I've never really tried the 151 at anything other than about 5KHz, it was hard enough keeping it stable for the pictures I took, but I assume that's due mostly to age. I expect you could use it to align a radio, even if you couldn't see the cycles you could still see the trace grow and contract as you aligned the IF transformers. Not sure why, even a decent tech can align by ear and an experienced tech would have no problem aligning.

I'm not sure if you can find it (anymore,) but a magazine called Invention and Technology published in the 1990s ran an article about a cooper in New England that had equipment so old that it was designed to run on low frequency AC. As it was still in operation, the electric utility was legally obligated to either keep the AC at the frequency required or update the equipment. Just was kind of neat to see stuff like that in operation decades after it went out of date.