Dr. Scott M. Baker

Eico 430 Oscilloscope

by admin on Dec.24, 2015, under Electronics Projects

I can’t resist buying vintage test equipment:

The Eico 430 is a tube-based oscilloscope. By that I don’t simply mean that it uses a Cathode Ray Tube, but that it uses vacuum tubes for the amplifiers and oscillators as well. It’s truly an amazing piece of equipment for the era that it was created in. The video above walks through my trying out the scope (it didn’t work right… does anything bought on ebay ever work right??) to me fixing the scope, and then using it in conjunction with a couple RF frequency generators and my sweep generator.

Now for some still shots:

Eico 430 Tube Era Oscilloscope

It’s probably not evident from that picture, but the scope isn’t actually working very well. The Horizontal gain control is fully clockwise, and there’s less than one division of horizontal deflection on the lissajous pattern that I’m displaying. I noticed the gain would improve at higher horizontal frequencies, and I decided to take a look at the schematic:

Eico 430 Schematic

I was immediately suspicious of C23, a 20 microfarad electrolytic capacitor connected to the horizontal gain capacitor. It’s an electrolytic capacitor that appeared to be original, and the attenuation at low frequencies would be consistent with a failed capacitor. I replaced it with a modern cap, and the problem was fixed:

Eico 430, lassajous pattern after capacitor fix

Here’s a picture of the replacement capacitor:

Eico 430, replacement capacitor

Well gee that turned out to be really easy. The scope works pretty well. I bought it with the particular purpose in mind of using it in X-Y mode in conjunction with a sweep generator, and that’s shown in the video at the top of this post.

Now for some teardown images:

Eico 430, view from underneath

Eico 430, Left View

Eico 430, right side

Eico 430, top view

As far as vintage gear goes, a vintage oscilloscope is one of the funner pieces of gear that you can acquire. Just beware that you might have to repair it yourself!

Here’s a picture of my Eico 430 in action, together with an Eico 369 sweep generator:

Eico 430 oscilloscope with Eico 369 Sweep Generator

1 Comment for this entry

  • Anthony Speros

    HI Dr. Baker I am looking for The Nixie Driver Boards you made for your kickstarter project because I want to build your nixie freq counter if the boards aren’t too expensive.

    just found you recently love the way you explain things and the type of stuff you do..


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