Heathkit IO-12 'Laboratory Oscilloscope' Restoration

Aaron Poffenberger

I went to Houston Vintage Radio Association (http://hvra.org) meeting this past weekend and picked up two used oscilloscopes during the auction.

I blogged about the Tektronix TAS465 here

Heathkit IO-12 "Laboratory Oscilloscope" Restoration


The Heathkit is an IO-12 "Laboratory Oscilloscope". These oscilloscopes were available from 1962 to 1968. It's vacuum tube based.

I got the Heathkit at the same auction for USD$5.00 (I really know, right!!!). As you can see in the image, it did work initially. The trace was not particularly bright, but it worked.

Black Beauties


Alas, after running for 10 or 15 minutes it blew a cap. They're 1600 VDC, 0.1 uF. I was able to find a newer (probably 20-years old) cap rated for 2000 VDC, 0.1 uF.

I haven't installed the replacement, yet. Probably this weekend.

Oh, and while I've titled the image "Black Beauties" these aren't real "Black Beauties" because they were made by General Instrument. Robert C. Sprague gave the name to a line of capacitors produced by his company, Sprague Electric.

Still, the name has often been used for capacitors like his.

Hand Built


One of the things I like about this scope is, like many Heathkits, it was built by hand. You can tell by looking at the soldering.

In the image above you can see where our unknown builder rebuilt a trace and touched a wire with the soldering iron.



I'm cleaning up the insides first. There's close to 50 years of caked dust inside. In the first place, it needs to be cleaned to work on. I've had trouble measuring continuity between points because the dust is so thick.

In the second, this scope is a real beauty with it's gleaming glass tubes and metal traces. It should look good!

MacroFab and the Montage


I'm giving a 3-minute quick talk about the Heathkit restoration at MacroFab tonight. I made montage of mutliple images to use as a single-image slide.

Take a look and follow along. (The image is much larger. Open in a new tab to see all the detail.)