[Swan] SW 240 lineage questions

[Rick Gouge]

Robert,I also have a SW240 in beautiful condition. I was trying it on AM 
along time ago and i guess i had the drive to high and had a RF flareup in 
the finally cage. Since then i can not get full drive out of it on SSB. I 
have alot of new 6DQ5. I put a new one in and no change. I also tested all 
other tubes as well. All are good. So i think it must have something to do 
with another component in the RF cage. I have a operators manual but no shop 
manual. I hope this makes some sense to you. I would be greatful for any 
help on this matter. Rick VE7RiK
----- Original Message ----- 
From: "Robert Nickels" <ranickel at comcast.net>
To: "Discussion of equipment manufactured by Swan" <swan at mailman.qth.net>
Sent: Monday, November 03, 2008 5:09 PM
Subject: Re: [Swan] SW 240 lineage questions


> Bill Clarke wrote:
>>
>> On the PA (6DQ5) pin 3 has a 5 watt 5 ohm ceramic resistor to ground.
>> It does not look original and is not on the diagram I have. What
>> might the reason for this modification have been?
> Bill, that's a hack to re-balance that leg of the series-parallel heater 
> string for use with the "dark heater" version of the 6DQ5.  RCA introduced 
> this version of the tube in the 60s as a "running change" i.e. no change 
> in marking or designation.  However the dark heater version draws 
> substantially less current than the original 6DQ5 and thus the Swan 240 
> filaments will be really unbalanced if one is just plugged in.   I did the 
> same thing to prove to myself that this was  the case before learning 
> about the dark heater issue and have been trying to spread the word ever 
> since.    In most applications with 6.3 volt filament wiring, the new 
> version was a plus as it required less filament current, but not for the 
> Swan 240!
>
> By the way, I'd recommend restoring it.  Several of us use them routinely 
> on the Vintage Sideband Net and I like the broader sounding audio.  It 
> also puts out a heck of a signal for having only one inexpensive final 
> tube!  I also have a spare TCU remote VFO console available if anyone's 
> interested.
>
> 73, Bob W9RAN
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