Restoring a Japanese Oscilloscope

Oscilloscopes have come a long way. Today’s scope is more likely to look like a tablet than an old tube-based instrument. Still, there’s something about looking into a glowing green tube, especially if you’ve done the work to resurrect that old hollow state device. [NFM] picked up a Kikusui OP-31C–a vintage Japanese scope at a second-hand store. He made a video of his restoration efforts that you can see below.

The scope actually powered up and worked the first time. Of course, unlike a modern scope, the OP-31C has to warm up before it will show up. However, the pots needed cleaning and as a precaution, he replaced the old oil and electrolytic capacitors.

The big transformer and the coarse-looking single sided circuit board certainly will bring back memories if you are old enough. [NFM] had a schematic of the scope and takes you on a tour of the innards, although his schematic had some subtle differences from the actual unit, possibly due to some repair work.

He was going to rebuild one of the large electrolytic “can” capacitors to keep the outer shell with newer (and smaller) modern capacitors. However, he found a very similar modern capacitor and used that, instead.

We think it would have been more fun if the scope didn’t work. However, it was still a great tear down of the old tube-based device. This is a bigger device than the last old scope tear down we looked at. Not that we haven’t seen smaller ones (although, the link in the post has moved).

5 thoughts on “Restoring a Japanese Oscilloscope

  1. that looks a t it working, along with lot like an old EICO scope I had, the 1S2 rectifier tube had failed, we gave up trying to get it going, along with a few others with the same fault.

  2. I really wish modern oscilloscopes would go back to the ‘vertical’ orientation with the screen on top, and the knobs / buttons on bottom. It takes up less desk space, for one thing. Even if it’s thin and flimsy plastic, how’s that any different than a tablet on a cradle?

    Also, that leather handle? Man, they don’t build them like they used to. That’s classy af.

  3. I love seeing old test gear being given the love it deserves. Sometimes it’s possible to get perfectly usable lab-grade stuff for very little money on the used market. Spend a little more to clean it up and re-cap it, and you end up with lab-grade gear that cost someone else thousands of dollars for potentially less than you spend on a night out.

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