need help identifying device

Scott Johnson scottjohnson1 at COX.NET
Mon Sep 29 20:48:59 EDT 2008

I don't think that is asbestos, I forget the trade name, but it is a
glass/mica loaded composite that was often used in old timey RF relays, etc.
besides, asbestos is not all that bad in hard forms, it is really bad in
loose form, as was used in steam pipe insulation. If you're really scared of
it, I'll take it off your hands!

Scott W7SVJ

-----Original Message-----
From: Boat Anchor Owners and Collectors List
[mailto:BOATANCHORS at LISTS.TEMPE.GOV] On Behalf Of Mike WE0H
Sent: Monday, September 29, 2008 5:22 PM
Subject: Re: [BOATANCHORS-TEMPE] need help identifying device

Don't take a deep breath around that baby. Yikes!!!


Chuck McGregor wrote:
> 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
>> N1MUC

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