[JMS] Variarm VFO

Brian Harris cosmophone at yahoo.com
Fri Dec 31 17:04:45 EST 2021 

I have two 90700. Neither have SO-239. I think UHF connectors came along slightly the 90700 was introduced anyway. 

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> On Dec 31, 2021, at 2:40 PM, Tom Elmore <tom at telmore.com> wrote:
> 
> Thanks Dave for the offer what I am really interested in is a picture of the coil under the little cover to see hoew the wiring looks.
> 
> -Tom
> 
> -----Original Message-----
> From: james_millen_society-bounces at mailman.qth.net [mailto:james_millen_society-bounces at mailman.qth.net] On Behalf Of David at Eppert.ca
> Sent: Friday, December 31, 2021 7:42 AM
> To: The James Millen Society Members Email Reflector
> Subject: Re: [JMS] Variarm VFO
> 
> Tom
> 
> I have both Millen VFO’s and they both have adapters that connect to the Millen transmitters via the crystal socket. I’m at work so I can’t send pictures but can send later today. 
> 
> David VE7CN
> 
> 
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>> On Dec 31, 2021, at 1:12 AM, Tom Elmore <tom at telmore.com> wrote:
>> 
>> Hello, I recently picked up a Variarm VFO model 90701, serial number 431. It
>> still had the original resistor line cord and I considered keeping it as a
>> display unit had the line cord been functional but as it turns out the
>> resistive element was open.  I did replace the cord with a black cloth
>> covered type that I found at Lowes marked as a Globe Designer extension
>> cord. I went with this type of cord because of its appearance and that it
>> also has a polarized plug on one end and on the other I cut off the female
>> outlets. I ended up using the capacitor & resistor combination shown below
>> to get the proper filament voltage and the sure resistor runs quite cool to
>> the touch. This unit is going to need a total recapping but what I did find
>> out was that I have B+ voltage live on the chassis. It took a couple of
>> hours of troubleshooting but what I discovered  was that the V2 25L6 buffer
>> tube has its output coil L2/L3 one tap goes to the chassis.  Can anyone tell
>> me if these VFO's ever  had a SO-239 installed on the side of the chassis as
>> the VFO output. The one I have has a SO-239 installed and it looks like a
>> stock installation. According to the schematic there are actually two
>> separate coils in the output here marked as L2 and L3. L2 is part of the
>> tank circuit and L3 is the actual RF output that is air coupled to L2.  In
>> my VFO though L2 and L3 are wound as one continuous coil with several taps
>> and someone at some point grounded one the taps to the chassis (a big no no
>> since there is live B+ here) and then capacitor coupled one the other taps
>> to the center pin of the SO-239. I'm thinking I could break the electrical
>> connection at one of the taps to provide a true isolated output but I wanted
>> to see if anyone had a picture of their coil arrangement they could send me
>> please.  Lastly what's the deal with the fuse in the schematic it looks like
>> it is only providing protection for the voltage doubler circuit and not the
>> filaments and this is how mine is wired also. 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> Volt Total=62.6
>> 
>> Current Total=.300ma
>> 
>> 
>> 
>> Capacitor 8.3uf 
>> 
>> Surge Resistor 33 ohm / 3 watt
>> 
>> 
>> 
>> 
>> 
>> Thank You 
>> 
>> 
>> 
>> Tom Elmore  KA1NVZ
>> 
>> Anchorage, Alaska 
>> 
>> 
>> 
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