I picked up an Johnson Viking ll transmittter at a hamfest yesteday. I
have the manual for it.

It has been modified in several ways with no docummnetation. One is
there are 2 voltage regulator tubes in series that connect to the large
power resistor with the slider contacts on it. Is there a published
modification for this ?

Another thing is on the 807 tube plates there is an added resistor of
about 25 ohms. It is similar to the paricitic supressor on the plates of
the 6146s but without the wire around it. This is the first time I have
seen resistors this way in audio circuits. I am mainly solid state,but
have worked some with tubes, but have not worked on many audio
amplifiers of any power.
What is the purpose of those two resistors ?

In article t,
says...

I picked up an Johnson Viking ll transmittter at a hamfest yesteday. I
have the manual for it.


I also found out the 2nd 6au6 tube has been replaced by a 6AQ5 tube and
seems to be rewired to match.

In article t,
Ralph Mowery wrote:


I picked up an Johnson Viking ll transmittter at a hamfest yesteday. I
have the manual for it.

It has been modified in several ways with no docummnetation. One is
there are 2 voltage regulator tubes in series that connect to the large
power resistor with the slider contacts on it. Is there a published
modification for this ?

There are a LOT of modifications for these things out there. I don't know
most of them.

If this is attached to R13, it's likely a shunt regulator for the
bias for the modulator. That would be a smart idea and probably bring
the distortion on the modulator down quite a bit.

Another thing is on the 807 tube plates there is an added resistor of
about 25 ohms. It is similar to the paricitic supressor on the plates of
the 6146s but without the wire around it. This is the first time I have
seen resistors this way in audio circuits. I am mainly solid state,but
have worked some with tubes, but have not worked on many audio
amplifiers of any power.
What is the purpose of those two resistors ?

There is normally a 22 ohm resistor in series with each plate for stability
and to act as fuses to protect the transformer in the event the tubes fail
into shorts. These are original, not modifications. Notice also 100 ohm
resistors in series with the grids.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article t,
Ralph Mowery wrote:
In article t,
says...

I picked up an Johnson Viking ll transmittter at a hamfest yesteday. I
have the manual for it.

I also found out the 2nd 6au6 tube has been replaced by a 6AQ5 tube and
seems to be rewired to match.

That's also factory. Do you have the correct manual for the thing?
Get the one from:
http://www.radiomanual.info/schemi/S...ing-2_user.pdf
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article , says...

I also found out the 2nd 6au6 tube has been replaced by a 6AQ5 tube and
seems to be rewired to match.

That's also factory. Do you have the correct manual for the thing?
Get the one from:
http://www.radiomanual.info/schemi/S...ing-2_user.pdf
--scott
--



Thanks for the info and manual link. I downloaded it.

It is dated 1953 where the one I have is 1952 and it does show the 22
ohm resistors in the plates of the 807 tubes that is not shown on the
schematics I have.

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.

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.

I hate it when there is a change and no difference in the model number
or maybe a letter after the change. I worked in industry at calibrating
and repairing instruments among other things. Some companies would make
a change and never show a different model number on the boards. Made
things confusing there also.

73 de ku4pt

Ralph Mowery wrote:
In article , says...

I also found out the 2nd 6au6 tube has been replaced by a 6AQ5 tube and
seems to be rewired to match.

That's also factory. Do you have the correct manual for the thing?
Get the one from:
http://www.radiomanual.info/schemi/S...ing-2_user.pdf

It is dated 1953 where the one I have is 1952 and it does show the 22
ohm resistors in the plates of the 807 tubes that is not shown on the
schematics I have.

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
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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

Ralph Mowery wrote:

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.

If plate and screen resistors failed, I'd replace the tube and see what
happens, because likely it was the tube that caused them to fail.

Check the supplies with a scope. If you see hum, you have decoupling cap
issues. If you don't, then it's something else.

You can also try pulling the first audio tube. Got a hum? If so, pull
the second audio tube. Still a hum? Pull the finals from the audio deck.
Still humming? You can track it down stage by stage... and it may well be
in the RF stages and not the audio stages.

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.

When the 6AQ5 develops a heater-cathode short, which they are prone to doing,
they usually hum SO LOUD that you won't have any usable audio. So I am not
going to put money on that... but you should have a spare handy since the
6AQ5 is a very common tube and you will encounter them in the future.

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.

The Vikings saw commercial service all over the place, and even found
themselves in broadcast service. As late as the 1980s, both HCJB and
one of the C&W stations in the Caribbean were using them as shortwave
broadcast transmitters, continuous key down for days on end. New, they were
not cheap by ham standards, but they were very cheap by commercial standards
and because there were so many in commercial service they turned up surplus
at good prices a lot.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article , says...

The Vikings saw commercial service all over the place, and even found
themselves in broadcast service. As late as the 1980s, both HCJB and
one of the C&W stations in the Caribbean were using them as shortwave
broadcast transmitters, continuous key down for days on end. New, they were
not cheap by ham standards, but they were very cheap by commercial standards
and because there were so many in commercial service they turned up surplus
at good prices a lot.



Yes, if used in commercial service the price is inexpensive. I guess
that explaines why so many of them show up at the hamfests. I had a
hard time thinking hams from around 1950 to 1957 could afford many of
them. Just like the $ 5,000 rigs and up of today. However it seems
with the 401k and such older hams like me have more money to spend.
Especially looking at the required takeout after 70 1/2.

I have a box of tubes from about 40 years ago when I did some repair to
the CB radios to pick up some extra money and learn repairing. Could
only find one used 6aq5 in the lot but my tube checker said it should be
good.
I did get on ebay and ordered a couple of the 6aq5 and 6al6 tubes that I
did not have. Found a bunch of the 6au6 tubes. Whoever designed the
Viking shure could use some learning on where to place the parts as the
audio tubes are difficut to get to. I have a couple of 6146 tubes but
did not think they need changing at this time as I can get out over 100
watts on CW and close to 100 watts on AM. I may try them when I am
satisfied the Viking is working like it should. I should be able to
find a couple of 807s at a hamfest that is comming up over Labor Day.
They should be ok as my scope shows that if I run the audio up I can get
well over 100% modulation.

I probably need to trace and draw out the modification made to the audio
stage. Probably should check all the resistors for value as most seem
to be the origional ones. I know sometimes they will change values
like the ones in the Heathkit amp I have did in the meter multiplier.

I hope to put it on the air in a week so with some friends that hae some
AM equipment.

73 de ku4pt