ICS Signal Generator

Front view

Top view

Bottom view

I would guess that this was a kit of some type. It's definitely not a professional piece of equipment. And I found one dry joint which tends to reinforce the idea.

I am not as good a draftsman as Roberta, but here it is.

Hand-drawn Schematic

Basically it's an Armstrong oscillator built around a 6AQ5 a.k.a. EL90. I suspect the light bulb is acting as a monode noise generator, based on the capacitive coupling to the grid (a direct or resistive coupling would have suggested stabilisation of the Bill Hewlett variety. Comments will be appreciated.

2016-08-22: Received pictures of a different model.

Keith's ICS

So ICS is short for "International Correspondence School". I was right then.

Keith's ICS

This one uses a 117L7 -- The 117L7 is a combination pentode and rectifier with a 117V filament. The filament is connected straight to mains and HT is just that same mains, rectified. That's what we call a widowmaker.

Keith's ICS


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