Identify that Transmitter!

[K8WBL]

Hello Group, I posted this some months ago with hopes of trying to find some origin of this transmitter.  Age appears to be somewhere around 1935 - 39 era.  Rack size is 22" width X 6 1/2 feet high.  Original tube line up was (2) RK-20 RF Finals, (2) RK-31 Modulators and (2) 866A rectifiers.  The speech amp was removed and it appears that the exciter was possibly different than the one in the transmitter currently, which is a Meissner Signal Shifter, 1st generation, repackaged into a 22" rack panel.  The plate transformer and choke are stainless steel clad Thoradson's.  The Weston fan meters are quite unique and I can't believe that this was all homebrew...it has been modified currently for (2) 813's in RF final and (2) 811A's in modulator.  I have traced one of the owners as a broadcast engineer at WLW in Mason, Ohio.  Where I used to live.  Anybody recognize this?

73, Tim K8WBL

[k4kyv]

I tried to view the details, but when I opened the attachment, the image that appeared was identical to the thumbnail.  When I enlarged it, the image just got blurry with no more detail; I think the thumbnails are the resolution limit.  I would be interested in seeing the rig in greater detail.  Did you save a thumbnail image rather than the full screen view?

[w1vtp]

Need the original pic.  No detail

[K8WBL]

Let me try this again..didnt go through first time... more pics..

[K8WBL]

And Yeah, thats a motorized cap on top there that was being installed.  Lots taken out of this transmitter including the tuning network in the top.  Just hoping someone might be able to recognize what this was at one time.. I have extra meters and the RK-20's,, etc...would be neat to restore it to original or near, if  possible...might not be, then will just keep the modded parts.

73, Tim K8WBL

[K8WBL]

Just noticed the plate transformer and choke is not installed in this pic, had to remove it to lighten moving...also.. newer parts that were mounted on the mod deck on separate bolt in chassis was a screen supply for the 813 and a speech amp power supply, no speech amp though...these looked much newer and were added later when it was being converted to the 813's.

Tim

[K8WBL]

One more...

[Opcom]

That is a real BEAUTY! I had some success by finding the offspring of an owner of one of my TX's. He clearly remembered his dad's building it, and I ended up with pictures and documents. Don't rule out homebrew. People back then had more time than money and if the guy was a station engineer he may have had money too, as well as access to all kinds of tools and even some 'deceased' transmitters or spare parts.

[N3DRB The Derb]

looks homebrew to me. I dont believe that's any sort of commercial job. Raytheon didn't have a lot of luck selling their own in house tubes to commercials. the fan meters are way cool. I believe those are Weston model 267 meters. very classy.

The RK tubes are getting hard to find, but cheap when you do find em as the audio maggotry doesn't want them.

That TX is well worth the effort of bringing it back, but for practical purposes, I don't think I'd be hanging with the RK's. they're just too hard to find.  2X 813's?  using a common supply with the 811's???  That sounds a bit fishy. how big is the plate supply? Sounds like too much current draw on one supply to me, unless that supply is massive.  stainless steel iron?  You must be referring to the CHT line.
nope. I looked harder. I have no idea who made that iron.

[KL7OF]

813's x 811's....A classic setup that I would stick with ....If the power supply is up to it, the 813's will produce a big carrier...Good Luck...Great looking transmitter..KL7OF

[W3RSW]

That's what I'm running 'cept the 811's are 572B's and the 813's are in parallel, not PP.
From a common P Dahl supply at 1500 to 2200 volts.  CCS 1 amp, tape wound silicon.

The beauty of a common plate supply having sufficient current, of course, is that the Class C RF amp presents a constant load, hence better regulation for the audio amps and driver stages.  Don't need a huge 150 watt, 25k bleeder.

[N3DRB The Derb]

here's the short data sheet on that era RK tubes.

the rk 31 and the 20 were very nicely matched together.

You gotta verify that the iron was upgraded or that he used a massive supply in the first place.

1250 volts is pretty lame for 813's. 811's would like it tho. maybe thats why he stuck 2 813's in there, to make up for that.   Who knows.

Its a hell o a nice transmitter.   Those Morrell caps are around 1935 vintage.

[Todd, KA1KAQ]

One of the things I've done when pieces-parts were missing was to use the original footprint (mounting holes, sometimes enhanced by dust) as a template to try different samples. Helps to have a big junk box or access to friends with parts of the same vintage. Might not tell you an exact value but can help getting the proper manufacturer or style. Once you find the type that fits, just tailor the values to your circuits and locate the correct value component.

Of course, it gets a lot more difficult when the chassis has been re-drilled or was a scavenged deck with extra holes to start with. At least the front panels looks to be fairly complete.

[K8WBL]

Thanks all, that is excellent information.  I suspect I got this in the middle of a major refit that never got finished.  The plate transformer (1200 volts) is too small for the 813's but may be OK for a separate power supply for the modulator, like my Globe Kings are.  I have a 2000 volt at 1 amp or so comercial transformer from Motorola UHF repeater that would make a good plate supply for the 813's, and probably just to make it simple for me, run the 813's in grounded grid. 

The workmanship on the front panels, along with the tube window cutouts, the beveled holes cut out for the fan meters, I thought this not homebrew likely, but you may be right about some engineers putting this together. 

73, Tim K8WBL

[N3DRB The Derb]

no doubt in my mind thats 100% HB. a darn good one. If'n you wanted it to be SUPA BAD you could run the RK's. You'd have a unique TX.

iron from a modern rig probably just wouldn't look like it belongs in there.

[WA1HZK]

It's the main power control panel from the Cryll planets power reactor / generator from the movie "Forbidden Planet" Did you also get Robbie the robot?

It's cool. You need to get it going. Looks like it would make a nice 4X1 Rig?
Keith
WA1HZK

[K8WBL]

Thanks Derb, you know I was thinking or atleast hoping it was some "known" transmitter so I could return it to near original...newer iron would look out of place and I can date this to 1935 +/- and would be neat to keep it with the RK-20's, I have seen them but not the RK-31's .. whole transmitter would only put out about 100 watts though.  The mod deck has a tag on it labeling it a class B modulator.


And I like the comment about it being part of the Cryll Power Reactor!!  It does have that kind of "feel" about it...hi hi


73, Tim K8WBL

[N3DRB The Derb]

if you find out what the iron is and what it's safely rated for, then you can start thinking about new tube choices. until you know that info, you have to assume that the supply is only made to handle what the RK's sucked down.

you could go with 812A's in the rf, and stick with the 811's. pair of 812's @ 1250 volts would get you a good 200+ watts and maybe a bit more depending on how much current you can squeeze out of the supply. 812's are cheap and available.

[W1GFH]

It's the main power control panel from the Cryll planets power reactor / generator from the movie "Forbidden Planet"

Don't forget what happened when Dr. Morbius tried to run QRO....

[KB2WIG]

Well, the Doctor spent too much time in the shop, and neglected his other duties.... Maybee Dennis, w7tfo, had the same problems when he was workin' on his radios.


klc