need help identifying device

Glen Zook gzook at YAHOO.COM
Mon Sep 29 13:19:31 EDT 2008

Can you say "diathermy machine"?

Glen, K9STH


--- On Mon, 9/29/08, WSHU Engineering2 <paull at WSHU.ORG> wrote:

From: WSHU Engineering2 <paull at WSHU.ORG>

My assistant  Tony just picked this Frankenstein device up at a live auction. Pictures are on the link below. It has two mercury vapor rectifiers (one broken) and two large triodes The triodes are type 3581, they look like 810s minus the side mounted grid pin, the grid connection is on the bottom pins. It contains a plate transformer but no filter cap, so the RF product would be modulated by the 120 hertz ripple.
It looks like a variable  push pull oscillator.The plate circuit is tuned by a cap with a knob on the front panel. I have not grid dipped it, but it looks like it is probably in the 20-30 mhz range.
Here is where it gets weird. The tuning cap is labeled Aux volume control, and a grid series resistor is labeled Main Volume Control. I took one of the 3581s out for the picture. What looks like metering jacks seem to be the input/ output connectors but the  grid coils on each side of the plate tank sure look like oscillator ticklers to me. Could be neutralization I  suppose if it is some sort of amplifier. Coupling of the plate circuit to the output jacks is via fixed air capacitors.
It has fillament and Plate switches on the front panel and a 500 mA scale meter for plate current.
120 volt input. Single transformer supplies fillament and B+ voltages
Pics at:


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