Johnson Viking 500 Power Supply/ Separated units?

[KW6T]

Having resurrected one Viking 500 in 2023, I now have another RF unit but with no power supply.  I am learning the likely reason the power supplies are separated from the RF decks are due to family members of SK's not realizing the heavy, ugly brown box is a part of another box on the shelf, and the brown box goes to the landfill.  Today, while my eldest daughter was here at the shack, we had a very clear discussion about my radio gear, and especially the 500 and its power supply. 

Given that, I do have an Invader 2000 power supply and no RF deck to go with it.   My plan, if all else fails, is to convert this supply to serve the Viking 500.  Is there possibly someone out here who is in a similar situation with an Invader 2000 and has a orphaned (but restorable) 500 supply?  Or someone who knows someone who ..........., etc?

I was going to post this in the "Wanted" section but was thinking I'd find a better audience here, and possibly open a discussion on the subject of separated units and possible solutions. 

In an effort to keep this discussion within the rules, if you wish to reply with a power supply for sale/trade or similar, please send a private message or email to:  rt998cc@gmail.com or to my email on QRZ.com.

Happy new year!

Thanks and 73.
Russ
KW6T

[W3SLK]

KW6T said:

Having resurrected one Viking 500 in 2023, I now have another RF unit but with no power supply.  I am learning the likely reason the power supplies are separated from the RF decks are due to family members of SK's not realizing the heavy, ugly brown box is a part of another box on the shelf, and the brown box goes to the landfill.  Today, while my eldest daughter was here at the shack, we had a very clear discussion about my radio gear, and especially the 500 and its power supply.

Given that, I do have an Invader 2000 power supply and no RF deck to go with it.   My plan, if all else fails, is to convert this supply to serve the Viking 500.  Is there possibly someone out here who is in a similar situation with an Invader 2000 and has a orphaned (but restorable) 500 supply?  Or someone who knows someone who ..........., etc?

I was going to post this in the "Wanted" section but was thinking I'd find a better audience here, and possibly open a discussion on the subject of separated units and possible solutions. 

I was going to let this one float but I saw your response in the other thread and thought I would chime in anyway. I think you are pretty close to the mark about Johnson 500 without their power supplies. I remember looking at some of the different auction houses where you would see them for sale but only the RF deck, not the power supply. The power supply would usually be offered in a different lot to bid on sometimes unknowingly to the bidder of the RF deck.
I seem to think that the power supply also had the modulation transformer sitting on it. Thus another reason that thing was so damn heavy. Check places like BAMA for schematics for both the 500 and the Invader 2K. You will probably have to make some changes to get it to work. I would opt for building my own PSU with a mod transformer. A while ago there was talk of using toroids as cores for modulation transformers on here which would reduce the weight. Dr. Google has the answers out there somewhere, you just have to look. Remember what Emil Faber said: "Knowledge is good!"
Good luck!
Mod-U-Lator,
Mike(y)/W3SLK

[Dave K6XYZ]

My plan, if all else fails, is to convert this supply to serve the Viking 500.

Thanks and 73.
Russ
KW6T

Not sure if the Invader 2000 has the correct plate xfmr but the Thunderbolt amp does have the same xfmr as the Viking 500.

The story goes is that the originally supplied xfmr was failure prone so EFJ warranteed the failed units with the Thunderbolt xfmr.
You are looking for about 2kv on the plate.
Both my J500 have the T-Bolt xfmr
Depending on how old you are....the best thing might be to look for another complete J500! 

I can tell you this....these are really great performing units and for the most part...bulletproof if set up correctly.
Search my name here and you'll find some of my experience with this unit.

[KW6T]

All,
Thank you for the responses.  To answer some questions,  the Invader 2000 power supply uses the same plate transformer as used in my Thunderbolt amplifier and in my  currently operating Viking 500.  The 500 currently inline is a very sweet transmitter and good performer; it was a dusty barn find that took about two months to rebuild.  Folks on the AntiqueRadios site were very helpful.

The Invader 2000 supply is the same physical size as the 500 supply.   It will be converted.  Chasing down parts now and will use some modern technology in the mix.   Hammond lists their version of the P.W. Dahl modulation transformer; that will be the likely mod iron used.

Happy new year!
Russ
KW6T

 

[Pete, WA2CWA]

I see Russ we must have been typing at the same time  Sounds like you got a plan.

As Mike and I indicated, the Johnson  500 requires a separate power supply and modulator. The Johnson Invader and Invader 2000 were designed with SSB in mind so there is no plate modulator. In the Invader ssb generator section, they use upper sideband and inserted carrier to generate AM. I didn't check the overall specs on the Invader 2000 power supply section to see if, at the very least, it could power up the 500 circuits. Again, if you were going to build a modulator, it would have to include a power supply for it.

Now, thinking out loud, you might want to consider a cathode modulator for the 500. They are simpler in design and don't require a modulation transformer. They are not as efficient as a plate modulator, but, in my opinion, they can sound just as good.
Here is a cathode modulator thread from AMfone back in 2016: http://amfone.net/Amforum/index.php?topic=41170.0
You can Google for more info; also, screen modulation might be another possible avenue to pursue.

[Pete, WA2CWA]

Quickie: Ya haven't gone crazy!: I removed all the posts in this thread that weren't relevant to Russ's original query. i.e. technical query in the technical forum should be "technical"

[KW6T]

Thank you Pete. 
That link is informative.  Given all its positives and negatives, I prefer plate-modulated AM.  To use any other method on the Viking 500 would be a sacrilege, IMO.  In any case, converting the Invader 2000 power supply will be a challenge and an interesting project.

73,
Russ
KW6T

[MikeKE0ZUinkcmo]

Hi Russ,

I've looked at the schematics of the two supplies and the Invader supply should give you all the voltages you need for the 500 with little modification.   The 2K supply chassis is actually two separate supplies, with the standard invader's supply chassis mounted into the 2K HV supply cabinet.   The invader supply should easily handle the 500's B+, plus what ever modulator you come up with, because it had a pair of 4-400s instead of the 500's single tube final, and the "LV chassis" handled all the straight Invader's B+ including the pair of 6146's in the PA, so here again it should handle a Modulator easily.   The two supplies (500 & 2K) are very different designs in some areas for sure, but should be easily made "power compatible" for your EFJ-500.   Of particular note is the different methods by which the bias voltages are generated.

I have both a 500, a very nice reliable transmitter, and two each of the standard 6146 PA invaders as well as a pair of 2K invaders with supplies that are at this time complete, but in Unknown working condition, another project.

Keep us up to date on your progress, as I for one, really like having a "ring side seat" hearing about the progress others are making on their projects.

Mike

[W3SLK]

MikeKE0ZUinkcmo said:

Keep us up to date on your progress, as I for one, really like having a "ring side seat" hearing about the progress others are making on their projects.

As we do about your projects Mike! I think every time I visit your 'smugmug' site I find something worthwhile!

[KW6T]

Thank you Mike. 

I am getting more familiar with the 2000 power supply and am hoping the transformer of the "200" section will work in lieu of T301 in providing the 6.3V heaters and the medium 350VDC +- for the audio and intermediate RF stages.  The HV transformer in this 2000 power supply has an identical model# to that in the 500 supply, so no worries there.  Also planning to eliminate the monstrous resistors; hoping to take the screen supply from elsewhere, regulate and switch it in simultaneously with the plate volts; the screen only needs around 30 mA at 500V.

Still evaluating the RF Deck.  It has a strange mod to the keying that makes no sense, so it will be restored to the original schematic.  The onboard transformer is good, and all tubes but the 0A2 in the VFO tested well on the TV7-D/U.  The infamous resistor had already been changed out.  I'd like to have it operating on my current 500 supply before pulling the trigger on a Hammond (Dahl) modulation transformer.  Hoping for the best.

I also have a site that contains some of my projects: www.rtsradio.net  Some photos are a few years old.

Will keep you posted.

Russ

Hi Russ,

I've looked at the schematics of the two supplies and the Invader supply should give you all the voltages you need for the 500 with little modification.   The 2K supply chassis is actually two separate supplies, with the standard invader's supply chassis mounted into the 2K HV supply cabinet.   The invader supply should easily handle the 500's B+, plus what ever modulator you come up with, because it had a pair of 4-400s instead of the 500's single tube final, and the "LV chassis" handled all the straight Invader's B+ including the pair of 6146's in the PA, so here again it should handle a Modulator easily.   The two supplies (500 & 2K) are very different designs in some areas for sure, but should be easily made "power compatible" for your EFJ-500.   Of particular note is the different methods by which the bias voltages are generated.

I have both a 500, a very nice reliable transmitter, and two each of the standard 6146 PA invaders as well as a pair of 2K invaders with supplies that are at this time complete, but in Unknown working condition, another project.

Keep us up to date on your progress, as I for one, really like having a "ring side seat" hearing about the progress others are making on their projects.

Mike

[KD6VXI]

Use a string of electrolytics off the plate supply.

Tap at the first or second for screen voltage.  Regulate from there.  Way less lossy, less voltage to drop from resistors, etc.  Even turns on and off with the plate supply.

You can use some smaller value lytics for this in parallel with a good oil cap. 

One way to skin the cat.

--Shane
WP2ASS / ex KD6VXI

[KW6T]

Folks, 
With this new-to-me RF deck, I am finding more wiring issues such as conductors attached to rotary switch clips where the schematic shows no connections at all.  I'm afraid this will be a long-term project..     Hoping the Viking 500 build manual will hold some clues.
Russ

[WQ9E]

Russ,

The easiest approach for you is to go ahead and take the case off of your other 500 deck and use it for reference while rebuilding the new one.  I have done this a few times with rigs that had been heavily modified by a prior owner.  The manual is helpful but having a properly constructed example side by side makes things much more clear and simple.

Rodger WQ9E

[KW6T]

Russ,

The easiest approach for you is to go ahead and take the case off of your other 500 deck and use it for reference while rebuilding the new one.  I have done this a few times with rigs that had been heavily modified by a prior owner.  The manual is helpful but having a properly constructed example side by side makes things much more clear and simple.

Rodger WQ9E

Rodger
You are spot on.  That is exactly the approach I took in the past couple of days, and it has been very revealing.  The major changes found have been in switching and removal of conductors.  The wiring of the female 9-pin power port had been altered.  The male 9-pin port was broken and is now replaced.  

Somehow, I initially missed noticing VFO had burned as a result of the infamous 18K resistor.  This also explains an added RCA jack at the rear of the chassis to allow connection of an external VFO.   Unfortunately, a donor VFO from a Viking Valiant or Ranger is not a drop-in replacement due to the variable capacitor's different drive setup between it and the stage tuning.  Must swap out the board itself.
 
It may be ready for another test this weekend.  

Regarding the Invader 2000 power supply, with the stock layout, there is not enough available real estate on that deck to install the modulator.  It will be essentially stripped out and re-configured.  

73,
Russ
KW6T






  

[KW6T]

Finally found the 120 volt short in the RF deck.  When the 120 volt interlock was previously removed, the switched, shielded conductor was obviously too short to reach pin 2 of the accessory plug, so the user soldered it directly onto the Neutral tab on the inductor board--a perfect direct short.  I replaced the shielded cable with a new run to pin 2, and the unit now operates with the power supply.  350 volts are now on the deck, and the "new" VFO is working.   The high voltage fuses are left out of the power supply for the time being.

Another surprise.  The audio choke partly responsible for that famous Johnson audio has been hot enough to drip its wax into the chassis.  It was replaced with the Valiant choke. 

Question:  After running about five minutes, the Drive control was getting pretty warm, so I assume there is a problem there.  Any thoughts?

73.
Russ
KW6T

[WQ9E]

Russ,

It is normal for the drive control to get quite warm because, like the smaller Johnson transmitters in that family, it also provides the bleeder resistor for the B+ supply.  A 510 ohm resistor from the 350 volt supply is used to create the 300 volt bus and the 25K driver pot is in series with another 3.3K resistor.  So the 4 watt rated driver control is dissipating 3 watts in normal operation and this will go higher if the 350V output is on the high side.

This same pot runs hot in the Ranger, Valiant, etc.

These are wirewound pots that will take the heat.  The common failure mode is the resistance wire winding ultimately becomes loose, probably from heat cycling, and then the moving arm will catch and damage it.  The same mod used in the Heathkit DX-100 that uses a small pot and at TV horizontal output transistor (or other similar transistor) can be used if/when these pots become completely impossible to find.

Rodger WQ9E

[KW6T]

After replacing several missing and misrouted wires, the 500 limped to life today.  The Tune/Operate switch in Tune position, it produces 75 watts and only 45 watts in Operate position.  Audio is clean.  Swapping in another 4-400A yields identical results.  Sweeping the tank circuit with and antenna analyzer, a noticeable dip is obtained on all bands.  Tank doorknob capacitors test OK with an LCR meter. 

I must have missed something..any ideas?

Thanks and 73.

Russ
KW6T

[KW6T]

I should add the plate of the 4-400A is glowing dark red at 200 mils cathode current at 45 Watts output.

[WQ9E]

Check your bias voltage lines including the developed negative grid voltage on the 4-400A under drive to see if that is correct.  It sounds like the 4-400A may not be biased properly into class C mode which could be either a bias supply/divider issue or not enough drive.  As I recall, this was a kit built 500 so the grid metering shunt may be off resulting in far less drive than what the meter indicates.

At 400 watts in and 45 out, the 4-400A will definitely be blushing!

Rodger WQ9E

[MikeKE0ZUinkcmo]

Your output numbers seem the opposite of what they should be in that the operate output should be greater than the tune output value.   Just checked out a 500 yesterday and looking at the manual's tuning procedure and PA readings expected  I reviewed the schematic as well and noticed that the clamp tube's bias is changed with the tune/op switch, so as Rodger said be sure the -150 is fairly close to correct.   I don't know what the actual voltages are at the clamp tube's grid though, because the transmitter ran quite well and no "fixing" was needed.   The transmitter should give you 300+ Watts.   If the 4-400 is good.

What are you using as a modulator?    Do you have another 500 supply/modulator?
 

[KW6T]

Mike.

Thanks for the response.  Yes, I do have a good power supply/modulator that I am testing this 2nd 500 with.  Also two spare 4-400A's and one spare 4-400B. 

Taking a step back, I am doing what Rodger suggested.  After restoring some hacked circuits to the original schematic, I should have re-checked the resistances at the tube sockets.  That being done, there are some out of spec readings and some very out of spec voltages in the RF string.  This weekend, I'll get back to it; once it produces good RF, I'll order the modulation transformer and start on the power supply.  Bias voltages on the slider resistor were off a bit.  They are now better; however, I don't want to do any more adjusting of that resistor until everything else is in order. 

Also, the existing multiple scale meter is the wrong one for the 500.  I believe I have the right one (electrically) now but need to re-face it to match.  Until that is complete, it is not possible to properly tune it.

This week, the first 500 was out of service due to an open resistor but is back to 100% operation.  It is a sweet transmitter.  That is the goal for this 2nd one as well.

Regards,
Russ
KW6T