[Boatanchors] Johnson Viking II Audio Mod Question

[Al Parker]

Hi agn,
    Garey's memory is faster and has much more retrievable info in it than 
mine, he comes to my rescue often.
    I now remember that while researching the subject, once you discount the 
super/hifi/max opinions, the gain in the stock Viking modulator is plenty 
sufficient with the 2 6AU6's in it, it sure doesn't need 4 triode stages. 
Most of the series, Viking 1 & 2, Ranger, Valiant, etc., have almost 
identical circuits.  The work I did my V-1 was largely direct replacement of 
off-value resistors, leaky caps, etc., and kept almost the same ckt.  The 
interstage xfmr was replaced, mainly 'cuz the old one was open, but the 
orig. is said to limit response a bit.  I did incl. regulation for the 
modulator screens, to improve linearity, and regulated grid bias.  There was 
a series of articles in ER on Viking 2 audio mods which showed those 
addtions.
    The better interstage xfmr does help the low freq. dropoff, nice for my 
deep voice & a D-104 mike, no change on hi's.  I'm not in favor of 
increasing hi-end audio, it just makes the signal wider, and AM is wide enuf 
when run respectfully.
    FWIW, I had a Viking 2 in the late '50's, my first rig of substance 
after a DX-35, and spent endless hours on 10m AM enjoying the fantastic 
conditions.  Box stock, as most stuff was then when not too far from the 
production lines.
73,
Al, W8UT
New Bern, NC
www.boatanchors.org
www.hammarlund.info

----- Original Message ----- 
From: "Garey Barrell" <k4oah at mindspring.com>
To: <Boatanchors at mailman.qth.net>
Sent: Tuesday, July 10, 2007 11:54 AM
Subject: Re: [Boatanchors] Johnson Viking II Audio Mod Question


> Scott -
>
> That sounds like a poor adaptation of the Valiant preamp.  Take a look at 
> the Valiant schematic.
>
> The Viking II was always known for it's great audio back in the 50's.  The 
> Ranger was also known for outstanding audio.  Now I'm sure that was in 
> part due to the fact that many of us were using cathode or screen 
> modulation, but I really don't understand the need for modifying these 
> modulators.  We really don't need "high-fidelity" broadcast audio for 
> communications!
>
> My Ranger and my Viking II are stock!
>
> 73, Garey - K4OAH
> Glen Allen, VA
>
> Drake 2-B, 4-B & C-Line Service Supplement CDs
> <www.k4oah.com>
>
>
>
> Freeberg, Scott (STP) wrote:
>> I've got a gorgous Viking II with a messed up preamplifer modification. 
>> I've looked in ER and online Viking II audio mods, found several, but not 
>> like the one here.  The PO replaced both 6AU6 preamplifiers with 9 pin 
>> 12AT7s or 12AX7's.  The first 12AT7 provides two stages of amplification 
>> while the 2nd tube has both sections tied in parallel for a massive 
>> driver transformer drive.
>> Does that mod sound familar to anyone.  The circuitry for that mod is a 
>> mess with shorts, messy connections, burnt wire insulation, wires tacked 
>> on, etc..  The rest of the Viking II connections are clean, its just a 
>> mess in the preamp section.
>>
>> I'm thinking of just removing the mess, putting the 7 pin ceramic sockets 
>> back in, and putting back to original.
>> 73, Scott WA9WFA
>>
>>
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