[Swan] WtB Swan sw-240

[Rick Gouge]

Thankyou for all of the info Ken. When i was talking about the radio not 
loading to 160 ma... i was talking about LSB not am. It was after i tried 
running the rig on am and had the RF flair up  that i could not tune the rig 
easy on LSB . It still tunes up but not to full power on SSB. I get maybe 
half of what it use to do and i have change the 6DQ5 with a new one and i 
get the same thing.. Max i think i get just under 100 ma on the plate 
reading at dip.... Rick VE7RiK
----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at verizon.net>
To: "Discussion of equipment manufactured by Swan" <swan at mailman.qth.net>
Sent: Thursday, January 24, 2008 5:53 PM
Subject: Re: [Swan] WtB Swan sw-240


> On 24 Jan 2008 at 13:42, Rick Gouge wrote:
>
>> Hi all. I am looking for a swan sw-240 tri bander for parts. must
>> still transmit because those are the parts i need. I am sure the
>> problem is in the final section. Had an RF fire for a brief moment in
>> the final cage when i was on AM. Transmitter still works but it will
>> not tune so i can have 160 ma.
>
> UNDOUBTEDLY, your final RF choke is a large, spiral-wound piece of
> carbon by now. The bypass capacitor at the bottom of the RF choke is
> simply bypassing all your RF to ground.
>
> If the RF choke is open, the screen grids of the final amp tubes are
> probably toast as well.
>
> A Swan 240, when operated on AM, shouldn't be loaded to more than 60
> watts input.
>
> 160 mA, if your plate voltage is around 700 VDC, would be 112 watts
> input. If it is 800 VDC, that would be 128 watts input, which is a +100%
> overload for the rig in AM.
>
> Even at 600 VDC, 160 mA would be almost 100 watts input (96 watts).
>
> If you have been running it at 160 mA, no wonder it burnt up.
>
> At 800 VDC on the final, you shouldn't load it to more than 75 mA on AM,
> and if your power supply puts out 600 VDC, then 100 mA is maximum
> input.
>
> I would the check final amp plate RF choke and replace it, and check the
> final amp tube(s) screens to see whether or not they still exist.
>
> Good luck.
>
> Ken Gordon W7EKB
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