need help identifying device

Chuck McGregor cbmcg at COMCAST.NET
Mon Sep 29 14:14:40 EDT 2008

Sorry to add to your bad news, but that white panel behind the power 
tubes of your diathermy machine sure looks like ASBESTOS.

--Chuck N7RHU

WSHU Engineering2 wrote:
> 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:
> 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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