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The New WA1GFZ Super Valiant




 
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K1JJ
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"Let's go sailing, Tommy!" - Yaz


« on: March 26, 2018, 04:27:25 PM »

I figgered you Johnson enthusiasts (and homebrewers) would get a kick outa Frank's modified Valiant.  It's like a Pro-mod race car.  As you can see he used four 6146s for the finals, four 36LW6 sweep tubes in p-p parallel as modulators, a homemade mod xfmr, full Teflon wire rewiring, all ceramic tube sockets, super-strapping tank components and bandswitches, etc.  It's not finished yet but is running and in the test mode putting out a well-modulated 250 watts of carrier.  He is planning on a solid state audio driver - no transformers.  All self-contained.  (The mod xfmr fits on the chassis when turned 90 degrees)

I will add more pics as he sends them.  I would love to own this Valiant in its modified form!  I really appreciate seeing a rig that has many weaknesses turned into a reliable, optimized workhorse as Frank has done.

Tom, K1JJ

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Here are some of his comments that describe the engineering thoughts as he built it - over the last 6 months.   Those of you who know the Valiant well will recognize the tremendous amount of detailed work he put into it. Frank is a ham's ham when it comes to design and building...

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Frank said:

  W1CKI turned me on to a course load switch wafer that I rebuilt with new contacts. Now I have two wafers in parallel to handle the current. I blew a couple fixed loading caps so built a module with door knob caps. Also replaced the fine loading cap with a larger 500pf Johnson, There is just enough room to install a change over relay next to the connector once I decide what to use.

I used a bunch of transformers that failed the hipot test. They were 2KV output DC transformers that had to pass 5KV. The parts that failed didn't have enough insulation between the primary and core. The primary would never see 5KV so it wasn't an issue. I gave Dean a couple, W1CKI has one in his 6 meter amplifier. I rewound one to make this modulation transformer. The core material was pretty high quality and good for audio. I studied a bunch of stuff on designing audio output transformers and figured this one would work. It will modulate 250 watt output carrier but I will be happy if it plays at 200 watts. I'm running 900 volts on 4 straight 6146s. I will swap over to 6146Bs or 6293s once I'm happy. I still need to design a driver. One option would be to copy the one in your rig. I'm driving the 36LW6 screens with an external output transformer backwards using a sanyo 50 watt module. The control grids are grounded. I have 10 ohm cathode resistors to balance the load and have a 5.1 volt 10 watt zener in the common cathode line for bias. I think I only need about 70 volts of drive because of the parallel sweep tubes. I figure the modulator will do close to 200 watts output. I was also considering a pair of 12B4s as cathode followers. Not ready to put on the air yet still need control relays and the HV is on a variac for safety reasons. You can share pictures if you want. Enclosed is a picture of the final. I rebuilt the whole rig with teflon wire and ceramic tube sockets. gfz

My last day of vacation I made great progress. I did the low drive on 20m modification and now have good drive on all bands. Then I was carefully looking at the loading cap area. As it was just determined I can fit much nicer Johnson 500pf variable cap in place of the stock cap. It has just enough clearance to get by the new dual course loading switch. The corner of the chassis left open I plan to build a LV supply. Maybe 28VDC for the relays. I blew up a couple padder caps the other day. I have some 470pf Russian door knobs that may be pressed into service.

I would be happy to do 200 watts carrier on AM. The HV supply is a bit over 900V, transformer rated for 750W CCS. We will see once I try 6146Bs or 6293 pulse tubes. It will definitely need a fan when it goes back in the case.
The A3898, 13H primary is way too big and the A3894 8H primary is too light. S21 and S22 have high resistance windings and will not like the current. CVM4 is too tall and would need to be sub mounted. Tim was going to trade me a transformer but the primary inductance was quite low so it would haul big current below 200hz. He thought 4 tubes would drive it but the efficiency would suck for low end.

The core I have has high frequency laminations and its size will not require a large number of turns to get good inductance. The present secondary is 2000VAC and measures over 100H, So one half that would be 25H then add the gap spacer.  I would like to wind the primaries side by side so they are balanced. I may make a bobbin out of G10. Another option is to wind all three windings side by side with the secondary in the middle.  I have an area of 4 1/2 by 6 inches for the mod iron where the old LV transformer and one rectifier tube sat. i'm thinking 1.3:1 or 1.4:1.
This will be the worlds most expensive Valiant when I am done considering man hours. gfz  

Happy New Year. A successful winter vacation. I'm making 200 to 250 watts on each band with straight 6146s. I picked up a second course loading switch to parallel the wafers. I'll start on the audio once I get the step start and antenna change over relay installed. HV is on a variac for testing.
My plan is to start with 4-6DQ5s and move up to 6LW6s if necessary. I have an A3898 for testing but plan to wind a modulation transformer. I'm shooting for at least a 16H primary inductance. I have a nice 500 watt core with good thin laminations from La Pointe days.
The final tuning in my Valiant does not give me peak power output at plate dip. It actually happens at slightly less C. I can't duplicate the same power at dip with heavier loading. It is acting like my Q is low but I am running 15 to 17. My bias is -86 volts increasing to about -117 with drive. My screen voltage is 150 to 160 volts. The plate is 900 or 950 VDC. I can get 200 watts at dip but I can get around 250 watts with a slight detune. I wonder if you noticed anything like that in your 4D32 rig? On 160 meters 1.8MHz my plate tune is about 1050pf and loading is almost 5000pf. It is lower at the high end of the band.
I think I will end up running at 200 watts output on AM. This is with straight 6146s so "B"s would be a bit more power. I would just like to understand why the power limitation.
I just received the wire for the modulation transformer. I can start on the audio section soon. gfz

I just fired up the HB iron 1.37:1 It appears to work fine at 250 watts output. I see power going up on the Bird when I talk. I'm using 4-36LW6s the B+ is 900 volts and hitting 400ma of modulator current on peaks.  gfz

gfz


* Valiant 3.jpg (2283.25 KB, 4000x3000 - viewed 364 times.)

* Valiant 2.jpg (976.47 KB, 4000x3000 - viewed 346 times.)

* Valiant 4.jpg (3584.98 KB, 3000x4000 - viewed 336 times.)
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
K1JJ
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"Let's go sailing, Tommy!" - Yaz


« Reply #1 on: March 26, 2018, 04:28:55 PM »

More pics to come later...


* Valiant 5.jpg (2949.34 KB, 4000x3000 - viewed 271 times.)
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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Brrrr- it's cold in the shack! Fire up the BIG RIG


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« Reply #2 on: March 28, 2018, 08:36:51 PM »

Whoooo...

Smokin'!

Hope Frank runs the sweep tubes in AB2.

Can't wait to hear that. Cheesy
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_-_- bear WB2GCR                   http://www.bearlabs.com
K1JJ
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"Let's go sailing, Tommy!" - Yaz


« Reply #3 on: March 04, 2019, 12:04:15 PM »

It's been a year.  Frank has made more progress on his Super Valiant.   He will be adding the GFZ MOSFET audio driver when built.

Take a close look at the top and bottom.


(reposted with permission)  Frank said:

"Added step start, TR relay, better mode switch, filament transformer for the modulators, Mounted modulation transformer,  negative cycle loading with spark gap.
Still plenty of room for the audio driver and power supply. Still need to rectify the 36 volt CT of transformer grounded. I'll make plus and minus 24 volts for mic amp and relay power. I plan mic amp on a little board mounted to the shield for the mic connectors. gfz"


T


* GFZ VAliant 1.JPG (1991.42 KB, 4000x3000 - viewed 154 times.)

* GFZ VAliant 2.JPG (2598.86 KB, 4000x3000 - viewed 156 times.)
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
Steve - K4HX
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« Reply #4 on: March 04, 2019, 02:58:56 PM »

Nice. I need to do something like this to my Globe Champ 300.
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