Two Old Variacs


I found two old Variacs in my grandfather's basement after he passed away.

Here is what they look like:

They are both General Radio Co. VARIAC Type 200-CM.

I want to keep one original, as he used these in the 1930's and was a prolific inventor.

The other is cracked on the switch part, so that one is going under the knife to convert it to 3 prongs and properly ground it.

Anyhow, if you've ever wondered what they look like and how they work, you are in the right place.

Note: I am learning as I go, so I don't guarantee everything I say about these is exactly true. I am looking to get closer to Van Halen's "brown sound" of the first album by running my Ampeg VL-502 50 watt amp head at a lower voltage. I assume this will lower the headroom and cause it to clip at a lower level as well as color the sound. It will undoubtedly turn my guitar into a mojo cannon.


Here is a closeup of the switch and outlet:


With the switch opened, you can see the wiring. There is a wiring diagram at the end of this page if you want to peek ahead.


The dial is easy to get off, only 2 set screws:


The steel case is hollow:


Here you can see that the top blade-like part turns to tap different points on the transformer:


This shows the hot output wire that is soldered to the blade part. Its wire runs through the middle then connects to the output plug below the switch:


Here you can see the hot input gets soldered to one of the windings:


Then there is another tap that is not connected on this model. If you look back at the switch photo, you can see the top right terminal is not connected to anything. That is the one that goes to this second tap. I assume they made another model that used 220 volts. The wire that comes through the bottom is the hot output wire. If you look carefully, you can see the ground wire at the bottom of the windings at the very end as it goes behind the hot output wire and gets connected to the bottom left terminal on the switch enclosure.


Here is a wiring diagram that sums it all up:


I plan to update this page after I perform the surgery.

Thanks to everyone who has helped out at!


© 2011 ~ Molten Voltage ~ visionary effects ~

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