need help identifying device

WSHU Engineering2 paull at WSHU.ORG
Mon Sep 29 11:51:49 EDT 2008

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 

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:

Tony will probably put it up on e-bay if we can figure out what it is, but 
you can contact him at tpage at  should you want to offer something 
for it and save him the trouble of listing it.

Paul A. Litwinovich
Director of Engineering
FCC License  PG-GB 039245

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