813 Amp Build: Let's drill some holes!

[W9ZSL]

  Where to put the holes and filament iron?  You can see why a different tuning cap is needed!  It's fat at 7 KV and all I need is 4.5.  This is really cramped and I don't want to spring for a larger chassis but might have to to house screen and bias supplies.  Input tuning would be under the deck to the left with band switch and tune. far upper-left corner in the pix.  The Loading is a 1000 pf at 1 KV supplemented by switching in 5 micas with a shorting switch under chassis.  Is the choke in the right place?

The filament iron could be mounted under the deck but it's 3 1/4" in a 3" chassis.  It's a nice Stancor P-4096.  I'd love to get a larger chassis, but have you seen the price on those things lately?   Sigh!

Up-date.  Oh Joy, Oh Rapture!  Found a 13 x 5 x 3 chassis to bolt on to the back.  Shield between the chassis.  The chassis in the layout is 17 x 13.  I'll be 18" deep  Since the smaller chassis leaves a 4" gap (upper left), I can completely shield the input.

Mike
W9ZSL

[w4bfs]

is this just a leanyer or are you going to plate modulate it ? that plate cap looks ok to me but I would use an inverted mount (rolled over 180 deg) this will make for shorter interconnect between the plate components which does more to make a tx stable than about any single other thing ... it will also reduce the amount of capacity to ground which will help with 10 /15 meter tuning

[W9ZSL]

Plate mod with 811A's at close to 1.5KV into an NOS UTC S-22.  That tuning cap is overkill.  Besides it upsets the "Chi" or whatever.  You know, the fung sway balance.  We had an engineer at the local station where I worked.  He'd drill holes first and then figure out what he was doing.  We called his band-aids "tumors".

The search is on.  A Johnson 250E45 would be ideal...or didn't they make one?  I can't help thinking of two hooters on one chassis and there's just no visual satisfaction!   

[W9ZSL]

Beans,

I'm hoping to track down something at only 4.5 KV  Can mount it any way I want. This tumor is taking up too much room...and there's the fungy-sway thing.  This is my masterpiece.  You'll note in the one photo...vernier dials?  I'm looking for a way to adapt the classic Collins-style knobs to that thin shaft.  I want this to look retro.

Mike

[Donnie SWL]

Maybe you could stand it up vertical an use a different drive like they do in a johnson 500 transmitter...just a thought..

[W9ZSL]

I hear ya Donny, but this has to be a rack build.  I had a Johnson Ranger years ago.  Best xtr I ever owned.  Bought it off my chiropractor!  He had it mated with an SX-100.  A lot of hams in Rhinelander used those.  One of the best combos in ham history.  I had a Gonset G-33 and worked only 40.  Worked 39 states by 1964.

If you check out the 4-125A transmitter Collins introduced right after the war, obviously my 813 can't be viewed.  Or can it?  I'm making up for that in meters.  I have collected tons of the classic Simpsons.  The second Collins used a 4-250A

Two separate supplies; 2 KV on 813 plate with 1500V going to 811A's.

Separate exciter and speech processor/driver.  I'm using a pair of 6V6's through a 15 watt iron to hit the 811A's.  Beefed up frequency response.

As for the exciter, I'm building a souped-up version of the classic Heathkit AT-1.  I just scored a vintage set of coils and all hardware.

[KA2DZT]

Leave the 7KV tuning cap in there.  I have 9KV in my 813 rig.  Turn the plate tuning cap over, the stators should be on top.  The choke is in the wrong place, too close to the coil.

Is that a neutralizing cap behind the tuning cap??  if it is, that's where the choke should be.  Move the 813 forward a bit.  The neutralizing cap can go between the 813 and the tuning cap.

I have to take another look at your pics.

Move the coil back, it looks like it's overhanging the chassis.  Turn the loading cap over, stators should be on top.  Also you'll need to raise the loading cap so the shaft is even with shaft on the tuning cap.

Fred

[W9ZSL]

This is just a first draft!

[K1JJ]

Exciting.  The rig will never look better than when the parts are first mounted on the chassis... :-)  You are starting with a blank canvas. Spend a lot of time getting it optimized.

Take a close look at Chuck's 4-400A rig below.  Check out the RF deck and how well he planned things out so that the RF tank circuitry was short and direct -  and the leads were as low inductive as possible. Look how the band switch is integrated into the coils. And the tubes sit right in front of the viewing windows.

If that's not enough, the front panel has almost perfect symmetry. Amazing planning and brainstorming needed to pull that off.

His rig easily operates stably up on 10 meters even without neutralization.  This is the work of a master and a good example for any builder to strive for in quality.

 http://amfone.net/Amforum/index.php?topic=36463.0

T

[W9ZSL]

Yeah Tom.  I could always move everything to the right but I always liked the way Collins gear was laid out.  I'd still like to get a more compact tuning cap so I'll have more "wiggle" room.  As for that coil, it will be mounted on the front panel on the same plane as the Pi Net shafts.

[W7SOE]

Here is my advice, from a novice builder:

Put bolts in all the miss-drilled holes to make them look like they are supposed to be there.

Rich

[VE3AJM]

Mike is this a different single 813 project from the one you were talking about building in Feb. 2015?, or the ART-13 mod transformer 811a modulator with the single 813 final, musings from recent posts.

http://amfone.net/Amforum/index.php?topic=37800.0 and http://amfone.net/Amforum/index.php?topic=40407.0

I don't think we ever found out on here how the tx from Feb. worked out.

Al VE3AJM

[W9ZSL]

This isn't the same Al.  

I had picked up an ART-13 mod iron and I asked some theoretical questions about what tubes to use IN PLACE OF the 813/811A combo because I wanted to use those tubes for this amp project which has been evolving for at least 20 years.  I couldn't resist the ART-13 iron because it's NOS and cost only $19.  At the time I was musing about using a single supply with the 813/811A and the ART-13 then upgrading it with 2 supplies and the UTC S-22 Mod iron.  Dumb idea.  Waste of time.  Go big right away...this project.

I may get a plate transformer from a DX-100 or TX-1 and modulate a pair of 5933's with another pair of 5933's using the ART-13 but that is a back-burner.

This is project #1 and I still am swapping parts around. RF Parts has a single-gang 280 pf @ 4400 volts I can use for the Plate Tune.  I originally planned on using a 4-125A but decided to use an 813 instead. The good thing is I have gathered a large stock of alternative parts.  The bad thing is I have gathered a large stock of alternative parts!

Another reason this is taking so long is I wait until I find something that is in great condition.  This really isn't a junk-box project.

[W9ZSL]

  RF Just bought the RF Parts cap, a 280 pf @4400 volts.  I may also check out the loading cap from Fair Radio you recommended.  No wonder this is taking so long.  I'm always looking for something more efficient.  Oh, wait.  Dang, that's the whole idea, isn't it?  

[KA2DZT]

RF Just bought the RF Parts cap, a 280 pf @4400 volts.  I may also check out the loading cap from Fair Radio you recommended.  No wonder this is taking so long.  I'm always looking for something more efficient.  Oh, wait.  Dang, that's the whole idea, isn't it?  

You should use the 7KV cap that you're selling in the rig you're building.  With 2KV plate voltage and high level plate modulation  the voltage peaks can exceed 4KV and higher.  You'll end up arcing the 4400 volt cap.  The 7KV cap will give you the needed margin.  I used a 9KV cap in my 813 rig.  Look in any Handbook, there are charts for the voltage rating for plate tuning caps.

Fred

[w4bfs]

You should use the 7KV cap that you're selling in the rig you're building...

I dunknow, Fred ..... It's hard to argue with Fung-Sway, whatever that is !  javascript:void(0);

[W9ZSL]

You know.  It's the oriental (Japanese?) art of arranging a room or garden so that it is in harmony with you and the surroundings...something totally absent from the usual shack or workshop!

[w4bfs]

You know.  It's the oriental (Japanese?) art of arranging a room or garden so that it is in harmony with you and the surroundings...something totally absent from the usual shack or workshop!

yes, I see ... I suppose I can reconcile this to a saying from L. L'amours 'Crossfire Trail':

    "You should take some time to consider that.  You will get a more harmonious outcome."

[W9ZSL]

The good thing about my power supplies is they are dual-voltage so I can always drop the 813 plate voltage down to around 1700 to 1800.  I'll be starting there and see how it goes first.  I'm putting in the High/Low Power switch from a BC-1T.