Johnson Viking 1 1/2 modification

[N0WEK]

I got a good deal down in Kansas on a Johnson Viking I that had a new audio section put into it and the final tube was changed from the 4D32 to a 8643. He also solid stated the power supply and added PTT and tune functions. 4D32s seem easy to get and cheap but the 8643 not so much. According to his notes he also tried the 5894A and 829B tubes and got 80 watts out; he's claiming 100-120 output with the 8643. He took pretty good notes and seems to have converted it in 2004, calling it a Viking 1 1/2.

I haven't fired it up yet, but supposedly it works fine @ 100 watts.

Any ideas?

[KX5JT]

You could always change it back to the 4d32! They used to be 17 bucks from Fair Radio but they're about 25 bucks a pop now... .still not bad at all.

I can't seem to find a data sheet on the 8643.

[Pete, WA2CWA]

Some data info:
http://home.comcast.net/~n6jv/8643.html

[KX5JT]

And a little more:

8643: double tetrode.
Vf=13.5V or 6.7V If=1A or 2A.
Pa = 2 x 38W max.
Va = 800V max.
Vg2 = 300V max.
mu = 7.

Base: 1-7 = f,f. 5 = heater CT.
2 = g1-1
3 = common g2
topcap1 = a1
4 = common cathode
6 = g1-2
topcap2 = a2

[N0WEK]

Any idea of how robust the plate and mod iron is in the Viking I? I don't know how good an idea it is to try to pull more out of the transmitter than the 4D32 would do and the modulator may not make enough audio to get to 100%. It was probably converted when the 4D32 was expensive and harder to find. I've found good sources for both tubes and don't have any current spares of either.

I suppose I could get it up and operating and see how it does with the 8643 and just not push it hard. When and if the 8643 needs replacing I could then decide which way to go.

[KM1H]

There is sufficient audio for a pair of 6146's as the iron is the same as the II and Johnson sold many 6146 sub assemblies to Viking I owners when the USAF dried up 4D32 sales to civilians during the Korean war. That was the real Viking 1 1/2

I bought spares several years ago at 2/$20 when the USAF surplus first hit the dealers. Enough to keep the Viking, 32V2, and eventual HT-20 happy for decades.

Carl
Viking I and II CDC owner

[The Slab Bacon]

You could always change it back to the 4d32! They used to be 17 bucks from Fair Radio but they're about 25 bucks a pop now... .still not bad at all.

I can't seem to find a data sheet on the 8643.

John,
        4D32s got kinda scarce and pricey for a while, so people looked for possible subs,
8643 is a nice bottle, kinda best described as a souped up 5894. The 8643 was a tube designed for high powered VHF 2-way gear (mostly used in Motorola stuff) (note the 13.5v filament rating) I believe the 8643 was either a Motorola or Amperex part number and listed only in SOME industrial tube manuals. Those tubes used to be dearly EXPENSIVE, but the equipnent that uses them is now old and passe' and the tubes go for dirt at hamfests cause noone wants them anymore. A pair will absolutely loaf along and yawn at the 100w power level!!

[W1AEX]

As Carl and Frank said, there were some interesting substitutes to ponder when the supply of 4D32's dried up. When I faced this problem I ended up removing the original socket and built up a little chassis for 3 x 6146B tubes that bolts down above the hole for the 4D32. It worked out great, and the same tubes are still in there today. To take advantage of the potential for more RF output, I moved to an outboard 811A modulator with its own power supply and run the 3 x 6146B's with the original Viker's power supply components with 700 VDC @ 300 mills.

Rob W1AEX

[kg8lb]

Seems Johnson offered up an official 829B conversion when the mighty 4D32 became scarce. The OT in our neighborhood always called that one the "Viking 1 1/2".

[N0WEK]

I've got a data sheet here for substituting an 829B for the original 4D32 which looks like a Viking addendum sheet. It looks like the owner tried the 829B and the 5894A for 80 watts out and settled on the 8643 for 100-120 watts out. I don't know if he actually wired it up and tried it or if it was just what was in the literature of the time, although my understanding from things said here and elsewhere on the web it that the 4D32 became scarce during the Korean war. This conversion seems to have been done in 2004.

I can go either way for about the same price for tubes. I guess I'll try it like it is and if things work fine I'll just leave it as is and look for a couple of spare 8643s at the next fest in March. I believe that it was Da Slab Bacon, in an old post, who had the Motorola part number, which I have printed out.

Can anyone confirm that the same plate and mod iron was used in both the Viking I & II? If so, I won't worry about over stressing the iron with the higher power. It does have a small muffin fan and enclosure around the output tube. He wired up the two plate pins with separate parasitic suppressors which tie together at the top of the plate choke. He seems to have done a very nice job on the conversion.

I like that 3/6146 mod, very slick! What's that mini-box over in the xtal section?

[WD8BIL]

Yes, the V1 and V2 use the same iron. If you use the same voltages it won't matter what tube you put in there,

[W1AEX]

I like that 3/6146 mod, very slick! What's that mini-box over in the xtal section?

The mini-box holds a League Handbook circuit based upon a 40673 dual gate MOSFET to handle the antenna T/R switching between the Viking and whatever receiver is being used. There are no relay contacts to clean, and it hasn't failed (yet) in the 30 years it's been in operation.

Good luck with the project, the Viking One is a great rig.

:O)

[KM1H]

A pair will absolutely loaf along and yawn at the 100w power level!!

The 8643 is a dual tetrode with 76W total dissipation and goes right into the 4D32 socket. Only one is required.

Seems Johnson offered up an official 829B conversion when the mighty 4D32 became scarce. The OT in our neighborhood always called that one the "Viking 1 1/2".

Strictly a first response that was a stopgap measure until the Viking II 6146 module became available as a kit with a Johnson part #. It was simply a sheet of paper sent to registered owners. From historical notes Ive read Viking I owners were more likely to upgrade to the V-II (with a nice discount since they took a bath on selling the V-I) since the TVI measures were included and doing it to a V-I was a royal PITA. The V-I that I had in the late 50's had a home brew TVI enclosure made from copper window screen and thankfully I never had to change a tube.

Carl

[The Slab Bacon]

<snip> "The 8643 is a dual tetrode with 76W total dissipation and goes right into the 4D32 socket. Only one is required." <snip>

It sure does, but the pinout is different, so please dont confuse it as a drop in swap. You'll have to rewire the connections to the socket. Also the 13.5v filament is center taped, so you can parallel it up and run it on the standard filament supply.


  

[kg8lb]

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Not a Viking 1 1/2 but we called it the DX-150. Other breeds were adaptable to the three holer conversion. This one with a sheet steel sub-chassis as well.
  The transmitter had already been well hacked by the previous owner. For some reason he felt the need for a front panel xtal socket and a front panel neutralizing control. Of course the front panel xtal socket also mandated a wierdly placed authoratative looking switch. A real pity as the DX-100 was otherwise a very clean machine up until the ham-holes appeared.

[KM1H]

<snip> "The 8643 is a dual tetrode with 76W total dissipation and goes right into the 4D32 socket. Only one is required." <snip>

It sure does, but the pinout is different, so lease dont confuse it as a drop in swap. You'll have to rewire the connections to the socket. Also the 13.5v filament is center taped, so you can parallel it up and run it on the standard filament supply.

Same with the original 829B swap and all its children.

[kg8lb]

"Stop gap" or not, I actually prefer the 4D32 version over the V2 . The 829B conversion seemed quite common as threre were tons of these tubes in the surplus stream by then. I have reversed three of the 829B conversions over the years. Nice to find and unmolested Viking 1 without the hamholes so often found . Yes , I understand they were TVI generators . I sure wish hams would enhance their metal working skills beforenthey take axes and chisels to the gear.
  I passed on two Viking 1 transmitters that had the TVI "upgrade" before I found the one we are now using.  The TVI kit wouldn't be so unsightly if only done by a capable person. The chicken wire screwed into sloppily placed and pierced hamholes really degrades a nice old radio .
 If I had a hacked up chassis I would probably give it to someone that wants to hack it up some more.

Another rig that fell to tube conversion mania was the HW TBS 50. The 6146 conversion was a disappointment for many folks.

 Surely , the component quality in the Vikings was top rate .

[KM1H]

If I had a hacked up chassis Id go with two 4D32's, a new PS section, more drive and an external modulator. Luckily I dont have to go that route unless I sell the current one and decide to go a lttle crazy.

[KB7HTV]

I have 2 Viking 1's I was thinking of taking my one with "hamholes" (great, absolutely killing me with this term I had not heard ) and running a weird Old 829B just for grins, who cares how much power it puts out, I was even thinking about depowering it further to make it a PW rig, It would be cool to have a PW Viking 1 with "Hamholes"

"you guys are killing me"