The Superior Instruments Co. Model 76 Bridge part 3: Rebuilding the device.
Thursday, March 26, 2026 at 07:17:02
This thing had a rough life. It doesn’t really work right now save that it lights up and makes glow. Did it ever really work? Well…since I just wrote that, I think you can probably guess what I mean.
I can’t say I’ve seen a device that has corroded wire like this one does. Not all of them, just some.
It’s hard to see, but it’s speckled with green. I checked wires as I went, some needed replaced, some were replaced just because they were in bad shape otherwise.
The eye tube socket assembly.
Everything here was attached decently, but stuff just looked bad, and these wires were corroded.
Some new resistors and new wire, and it looks better. Still needs a bit of dressing, but that comes last.
The original builder put the eye tube at a weird slant. While the bracket itself can be moved on a slide, doing so puts the bolt for the bracket up against a terminal strip underneath because it was mounted opposite of how it should have been. That was corrected by just using a longer screw and some nuts as spacers. It’s not like this thing is going anywhere, so mechanical stresses aren’t a concern.
That’s all for the eye tube.
The grid cap for the 12C8.
This is the “signal tracer” portion of the unit, and it uses a WWII surplus tube, the VT-153/12C8. This tube was designed for radio service, and exposes one of it’s grids on the plate cap. That’s where audio is fed in for amplification. There are two parts, a resistor to ground that provides bias for the grid and a blocking capacitor for the audio so you don’t get DC in your device that’s under test.
That was easy enough to re-do.
Fairly standard work, there’s really nothing of note. It’s time to move on to the main body of the unit, and all of it’s “none of this matches anything you wrote down!” mess.
Next part of this series: https://wereboar.com … rest-of-the-rebuild/
Previous part of this series: https://wereboar.com … actually-in-the-box/
Wrapup and final thoughts: https://wereboar.com … -and-final-thoughts/