I'm Finally Building It, Imagine That! WHOO HOO!

[K3YA]

Mike, you have quite a nice selection of parts there!  With you broadcasting background you also have more experience then I did when I started my first homebrew AM transmitter.  Here's a picture of my homebrew rig that I started 30+ years ago and still haven't "finished".


Mine started off as a pair of 813's modulated by 811"s with separate power supplies, 'caus those were the parts that I dragged home from the Gathersburg hamfest.  Over the years it's gone through three RF decks, four modulators, several audio drivers, and countless power supply and control changes all in the same Par-Metal rack.  If I may suggest, build your rig however you want, but leave room for future changes, and additions where possible.

Two more suggestions.  First put the heavy iron on the floor, not on chassis that mount higher up.  It's too hard to lift and support heavy chassis. 

Second, a 4 foot rack may prove to be a little confining, space wise,  Save some rack space by building simple assemblies like power supplies on a flat piece of 1/8-1/4" aluminum rather then a three inch high chassis.  It also keeps the wiring up top where it's easy to get to. Something like this:


This particular chassis is an early power supply from my HB rig.  It once also had a plate transformer on it and taught me the folly of building heavy sub-assemblies.

Enjoy your project!

[W9ZSL]

  Yup.  That's either a "classic" Collins on the left or a real nice clone.  This Loudenboomer will look like a shorter version of that. 

I also have a chikkin box or two labeled "George Junior" that I was fixin' to build first.  I'm not sure what I will do with those parts including a Merit A-4005 and a Stancor A-4701.  That modulator came from the '62 West Coast too.  It has a 6SN7 driving a pair of 807's. The iron is rated at 60-100 watts (?!)  I have a Bud cabinet and was planning on an AM/CW rig. 150-170 CW and 120 AM with 2 x 5933's final and P/P 5933's modulator.  It goes without saying, that rig probably will never be built because putting George together will probably kill me and George Junior, hihi!  I still have the oscillator/driver from the BC-1T.  I turned it into a VFO.  Shoot!  Maybe I'll build a pirate.  My first one covered 2 miles on 880KC!  I put a stack of 45s on an RCA changer.  When the stack ran out the last song was "Lost Friend" by Duane Eddy.  Somebody was trying to tune in WLS 890 and heard the tune being played over...and over.  The headline in the paper, "Mystery station plays "Lost Friend"...over and over and out!  73!

[W9ZSL]

Not to worry.  Everything on the bottom power supply deck will be surface-mounted.  Rather than put a plate flat on the bottom of the rack I'm building a chassis with 2" sides to allow for the caster bolts and give me a larger base.  The Gates plate iron can then be bolted down on mounts already secured to the top plate.  Likewise all the other heavy iron.  If I need relays, I have all of them from the BC-1T...KA-CHUNGKK!!!!! BANG!  The sound of kilovolts being rerouted!  I had to reduce power at sunset.  How often do you think I forgot?  Eventually it was a KW 24 hours a day.  

I'll pre-drill on the flat plate, align everything and possibly breadboard again.  After that I'll put the 2" sides on the chassis, bolt it down and wire the main power supply and controls.  If that doesn't work.......... I also have a tranny that belonged to a HB supply for a Hot Water 100.  This is the perfect choice for a voltage doubler.  It's made for a solid-state rectifier.  It's 820 volts and no center tap.  I'm guessing it's good for close to 1/2 amp.  Hot dog.  I still have the chassis it was mounted on.  I could replace the big Gates plate iron with a 2500 volt supply in a heart beat.  Then again, that would do justice to a nice linear, ain'a?

[W9ZSL]

LOOK AT THEM 833'S THERE...SAME AS THE BC-1T.  Would have been nice except for the shorted plate iron.

[N0WEK]

Yeah, I like the power supply built right into the bottom of the cabinet, just like the Gates. The BC-1J has all the heavy stuff bolted to the 1/4 or 3/8 steel bottom of the cabinet. The holes are tapped so it doesn't need nuts on the other end of the bolts. I'm going to do something like that when I get to building.

I'll have to try to get up your way this summer sometime, you should be well along with construction by then.

I'm in Wichita, KS at the moment getting my annual three days of torture in Flight Safety's simulators.

Greg

[KB2WIG]

" The holes are tapped so it doesn't need nuts on the other end of the bolts. "

Thars always carrage bolts... no tappin necessary.

http://technabob.com/blog/2011/11/15/drill-bit-makes-square-holes/

klc

[W7TFO]

Yeah, I like the power supply built right into the bottom of the cabinet, just like the Gates. The BC-1J has all the heavy stuff bolted to the 1/4 or 3/8 steel bottom of the cabinet. The holes are tapped so it doesn't need nuts on the other end of the bolts.

Greg

What Gates actually does (did) was spotweld nut plates on the bottom of a 10-Ga steel sheet for transmitter cabinet bottoms.  It makes it look thick, but isn't. 

Most transmitter shops did the same thing, tho Collins/Continental used a .250 aluminum plate with tapped holes in lots of their TX's.

73DG

[N0WEK]

Yeah, I like the power supply built right into the bottom of the cabinet, just like the Gates. The BC-1J has all the heavy stuff bolted to the 1/4 or 3/8 steel bottom of the cabinet. The holes are tapped so it doesn't need nuts on the other end of the bolts.

Greg

What Gates actually does (did) was spotweld nut plates on the bottom of a 10-Ga steel sheet for transmitter cabinet bottoms.  It makes it look thick, but isn't. 

Most transmitter shops did the same thing, tho Collins/Continental used a .250 aluminum plate with tapped holes in lots of their TX's.

73DG

I had the cabinet on it's back when I mounted the heavy duty wheels to the bottom plate and I don't remember those, I think mine has a solid plate but I'll have to find the pictures I shot to be sure.

The Bud cabinet I found has castors but I don't think they're heavy enough for a buzzardly transmitter and the bottom plate is too thin. I'll probably double it up with at least a 1/4 plate to mount the wheels and the iron. I'll mount the wheels recessed.

I used heavy duty, non swivel, steel wheels on the Gates for strength and stability; it'll allow me to pull it away from the wall to get into the back but I'll have to slide it sideways if I want to aim it somewhere else. With them mounted to the bottom plate they only raise the cabinet about 1 1/2 inches off the floor.

[W9ZSL]

BIG HONKIN' CASTERS!  I salvaged my Gates on-site.  It had been outdoors covered with a tarp.  August with temps pushing 90.  All that was left was the shell.  It did have threaded base plates.  I'm doing some re-thinking.  I have some 1/8 tempered pieces used in building control panels for boat lifts laying around.  Problem is getting them cut.  Maybe the guy from church could do it.  That way I have two separate supplies.  The plate supply on 1 and Screen/bias on the other on the bottom.  That way all I'd have to do is cut the .1 and use it for the front panel of the RF deck.  It's not thick enough to tap.  I'll play it by ear.  Most likely I have the original bolts.

Question: I'd like to put my pix or something here.  Not sure how to do it.  I cope with my computer and that's about it, hihi!  Greg, can that tuning eye squint?

[W9ZSL]

I actually have a solid-state supply I built awhile back to use for Plate, screen and bias.  It's a honey.  I had it for another project that never quite panned out.  It put out 775VDC; 550VDC under load to a pair of 5933's.  I have something like -140 volts.  I run it through one of the bias pots from the Gates.  The bleeder is tapped for the PA screen.  It has a big terminal block.  It also has a 6.3AC tap.  That transformer is a UTC and it was built for bridge use. The two octal sockets are for VR tubes.  I was planning on 180 volts regulated for the modified BC-1T oscillator.  I substituted coils for the crystal and have a rock-solid VFO  I got the thing to work just below 160 meters.  I need to wind a new coil.  I gave up on putting up a 160 meter antenna and in spite of everything I did never could get much out of it except SWR.  That's it in my last blab. 

[W9ZSL]

  Off and running.  Now that I have room to move in the shop I'm going to punch out the caster bolt holes.  I have a pair of 1/8" hard aluminum sheets on hand I could put on the bottom for the power supplies... one 10 x 17 for the plate and one for the  terminal block and relay/s if I use them and that screen/bias supply.  I'll need to size them so I'll have a pair 10" wide x 17" deep.  Right now they are 19".  They fit side-by-side in the bottom of the rack just perfectly.  Our local college has a metal shop with a hydraulic shear.  They have done some stuff for me in the past so I'll get 2" cut off there.  The 20" x 16" x .1" I was going to use to build the bottom chassis can then be sized to form a shelf for the tuning net.  That's how the Gates was set up.  I have a couple 17" x 11" x3"s but the tune breadcutter is also 11" so the fit would be too tight for an RF cage without drilling a hole for the end of the shaft.  The RF deck will be on one.  Hmmmm.  Maybe I can mount the Plate supply on the other.  Decisions, decisions.  Ain't it fun! 

[W9ZSL]

   What exactly did Lincoln say when he was presented with the plans for the Monitor???  Looks like this is a shoe-in?  Choke input is 15 HY at 250 ma, navy issue.  The 4-125A won't draw more than 175-200ma.  The cap is a 12 uF at 4KV.  The bleeder is from the Gates and is 100K at 175 watts.  I included a shot with the screen/bias supply and another with the tuning parts inside the RF deck chassis.  There's something in there indeed!  I can hardly wait to drill into that chassis!!!  Note there already is a wire coming off the SS rectifiers (Gates) that screws right on to the choke.  Too natural to ignore, hihihi!  I also have a 8 at 3 KV cap I could substitute.  Looks like a plate supply to me,  Separate supply for the mudulator.  Whoo Whoo!

[W9ZSL]

The power supply won't fit on the modulator chassis so.....  Thordarson is on the right with a choke and 1 cap.     I pulled the Navy choke for the plate supply and stuck in a UTC 10Hy at 350 mills.  The Thordarson will give me 1250 for the modulator.  NOW.  There is room for only 2 chokes.  Given I'm using separate supplies and have just one swinging choke, where should it go or don't I even need it?  I can put another filter stage (smoothing) on either chassis if necessary.  The navy is too big.  I believe the UTC is a CG-104.  The one in the pix is a Triad swinging 20/4HY@40-400 ma at 3KV.  I also have a Thordarson 12Hy at 300 ma.  The cap is a 4ufd at 3KV.  Am I right thinking using the swinger down below for RF is better than using it for the AF?  I can go either way  The UTC will fit fine on either AF or RF deck if needed.  I don't think I need another swinging choke.  The question is where will it do the most good?

[KE6DF]

I'm getting a little confused about all the chokes and transformers, but my general thought is a swinger is less useful for an AM final supply.

The reason is the final draws a lot of current constantly. So perhaps use the smoothing choke there.

On the other hand, a swinger in the PS makes sense for the Class B modulator as the current varies considerably and the large inductance at low current helps with regulation.

With today's larger caps, one stage of filtering should be enough. You needed multiple stages back in the days when 4 mfd was a big cap.

[W9ZSL]

If I were building a single supply around the big iron, there would have been two stages with swing followed by smoothing. A 12ufd would be between and an 8 or 4 on the end in parallel with the bleeder for the modulator.  

I'm going to use the UTC 104 on the plate supply...10Hy, 350 ma...the round one.  The supply on the right has a Thordarson 3160 CT in the upper right.  Next down is a pair of 866 solid state rectifiers with the swinging choke on the left of a 4ufd at the far lower right.  That will be replaced with the 8ufd. On the modulation deck I can put a smoothing...the Thordarson 12Hy @ 300 ma with the 4 ufd and a bleeder.  The filament iron will be under the deck.  No need for a bias supply.  I have to leave room for the driver xfmr.  Basically using two power supplies makes all the difference and the swinging choke in the AF makes more sense so the smoothing will be on the modulator deck if I want to add weight or if it is necessary. The modulation bleeder is a 60K new in the box.  BIG watts. Too much fun!   Yo, 'yall, does that make sense?

[W9ZSL]

Does anyone have a nice 5 volt filament iron?  Should power a 4-250A so, 15A???

[W9ZSL]

   This stuff will be moved around some yet.  The plate iron will be more to the top center in this side view allowing room for the fuse block and/or relay/s.  The front is to the left.  That is a 13" x 17" x 3" chassis.  On the bottom I just laid down a sheet I had on hand.  That supply will be for the modulator.  The Thordarson is at bottom right.  That one will be larger and mounted on a 1/8" panel I'll cut to fit so the parts will be stretched out.

Here is the parts list for the PA supply.  Plate iron from the Gates BC-1T-250 which is 3600VCT and worth close to an amp I'm guessing, two 8008 tube replacements, the CG-104 and the original 8ufd @ 3KV.  Bleeder will be under the chassis.  It will be 240V primary.  The mud supply will be the Thordarson.  It has a 115 volt primary and two secs...3120 and 2500 at 300 ma, CT.  It will be more spread out to 17".  I also have a Thordarson 12Hy at 300 ma and 5KV on standby.  That would go in the Mod deck if needed.  The diodes are 866A replacements.  Choke is the Triad swinger 4-20HY at up to 400 ma.  The cap is 12ufd at 4KV.  Bleeder can go on the Modulator deck with another choke and/or cap. How am I doing?

[KE6DF]

Are you sure you don't want to put a rectifier filament transformer on the PS deck so you can put real 8008's in and "see the glow".

[W9ZSL]

The 5V iron is for a 4-250A PA filament.  I have another xfmr for a 4-125A but I'm building for expansion.  Collins came out with a unit right after WW2 which was similar to what I'm working on.  It was upgraded to a 4-250A version later.  I have the 4-125A now but can plug in an up-grade any time.  

The rectifiers are all solid-state from the old Gates BC-1T and will do fine.  While I like the mercury bottles glowing blue (or as we used to say, "Blowing Glue") I'd have to buy them and besides, this way I probably won't need a plate relay.  Don't worry, I'm going to put a window in both the PA and Mod decks so hopefully there will be a nice light show and the 811A's will Blow Glue Too, hihi!

[W9ZSL]

  The plot thickens.  I dug out a cute little 10Hy, 200 ma 3KV Thordarson choke.  It fits on the Mod chassis perfectly along with the 4ufd cap.  You all got it right.  When it starts going together there's no stopping it!