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Ralph Mowery · July 9th 18, 10:15 PM posted to rec.radio.amateur.boatanchors

In article , says...

I have 2 (now 3) schematics that are slightly different. However they
both show a 6AU6 tube as the second one in the audio amp driving the 807
tubes. The Viking 2 I have has a 6AQ5 tube in that place. Maybe it is
factory like you say and I need to look for another schematic. I know
for the short time I have looked on the internet there have been many
mods for the audio stages. The older schematic does not show it,but the
newer ones show a 6AQ5 for the screens of the 6146 tubes.

OH! You mean the second AUDIO tube was turned into a 6AQ5, not the second RF
tube!

Yeah, that wouldn't be factory, that would be a modification, and likely
a good one since the 807 could benefit from more drive.

The second RF tube is also a 6AQ5 in all but the first few units. It sags
a little from Miller effect on 10M but is generally a good plan.

I know there are many modifications to it. A ham gave me some old QST
and CQ magzines from the late 1940s up to the 1970s. I do remember
seeing a few mods for the Viking 2,but would never be able to find them.
I looked on the internet and it is also full of mods.

Yes, these were inexpensive and reliable radios that were in common use for
many years, so as technologies changed people adapted new stuff for them.

My guess is that the combination of the regulated bias and the 6AQ5 probably
improve the audio quality a good bit over the stock unit especially with high
duty cycle signals.
--scott

Yes, the second AUDIO tube,not the 6AQ5 in the RF stage. Guess that I
was not clear on that the first time.

From what I have read, there does seem to be lot of mods to the audio
stages. Ihave not spent too much time with this unit so far. Got a
couple of crystals from a friend this morning sowas able to load it on
40 meters into a dummy load. Cw seemed ok,but no audio. Driving it
with a audio signal generator I could get a slight ammount of audio
out,but it took about 5 volts into the mic. Way too much. Found the
plate and screen resistors open on the 1st audio amp. Replaced them and
getting over 100 % when using a D104 mic if I turn the audio all the way
open. I am showing about 10% hum on the Viking on my ifr 1200s and can
hear it somewhat on a receiver in the other room. It is that way in CW
or Phone. Most of the capacitors have been replaced, but could be bad.
Maybe a HK leakage in one of the tubes. Ihave some 6AU6, but not any
6AQ5 tubes. That 6AQ5 was good for around 5 watts of audio and used in
many receivers as the output.

The Vikings were not that inexpensive when new. The book says $ 279 in
kit form. A friend that is much older than I am told me it was about $
100 more if factory built. It todays dollars, that is probably a 3 to 5
thousand dollar rig.

73 de ku4pt