The AM Forum

Hello All, I tried this last year with no success, so I thought I would try it again this year.  I bought an old (1938 was told) 6 foot plus transmitter from a guy in Dayton, OHio.  He got it from a couple of guys in Cincinnati, where I live now, it was traced back to an engineer, now SK, at WLW.  Tube compliment has changed, but this is what the original tubes were...

PA - (2) RK-20
Modulator - (2) RK-31
HV Rect. - (2) 866A 

New Tube set up

PA - (2) 813
Modulator (2) 811A
HV Rect. (2) 866A


I want to restore it, its absolutely beautiful. Will likely keep the current tube compliement, it appears it was never in service with this latest configuration. The final (tuner) unit was removed and a motor controlled variable Cap installed to tune the final...swinging links above and below the RF Pa deck.  Thoradson transformers (stainless steel overlays on them)

Also, the speech amp is missing and the exciter is a repackaged Meissner Signal Shifter...first model 1938.  It has a different textured front panel and obviously there was a different exceiter.  Also - rack size is 22" wide...not 19".

Thanks... 73, Tim K8WBL

Nice!!!

I love those meters!

N0WEK said:

Ditto! I was thinking the very same thing!

The 811-A is probably the closest thing available to-day to the RK-31 (http://tubedata.itchurch.org/sheets/081/r/RK31.pdf).  The RCA 814 (http://tubedata.itchurch.org/sheets/049/8/814.pdf) (plentiful from post-WW2 surplus) is closer to the original RK-20 (http://tubedata.itchurch.org/sheets/084/r/RK20.pdf).

The original Raytheon tubes both had 7.5 volt filaments and 40 watts of plate dissipation.

It would be neat to find some original tubes and restore the transmitter back to the original, but good  Raytheons would be hard to find. 

The 813's are a little overkill, though.  814's would be closer to the original, but still with more plate dissipation.

I have a couple of meters like those, but nothing like a complete set.

Something tells me each of those meters was probably a weeks wages or more in the day.  Am I right?

Thanks Don and others.  I have been buying up spare meters for this project over a year now, have about 3 or 4 extras.  Actually the guy I bought this from supplied me with 2 extras, some bulb covers and some metal cosmetic strips for the front and sides.  I thought about restoring it back but it has so many changes to it.  I could change out the 813 sockets and put some 4 pin ones back in, but all the antenna tuning portions were removed on the top section of this transmitter.  I have purchased some RK20A's but have yet to see any RK-31's on epay.  Now that I completed my Globe King 400B, maybe I can start getting more serious about this.  Taking back to original is not possible as I don't know what is original, except power supply, mod and RF deck, the speech amp is gone as is the exciter, no idea what was used.  No idea if this was initially a commercial transmitter or a HB project from the start.

Still have 2 more Globe Kings (400C and 500A) to restore as well.  Will keep searching for parts for this Big Guy - calling it little WLW for now, due to its roots...hi hi

73, Tim K8WBL

The Taylor TZ-40 (http://www.nj7p.org/Tube4.php?tube=TZ40) is close to the same as an RK-31.  Same filament voltage and plate dissipation.  Here are some photos.  Notice two distinct envelope shapes, one straight sided and the other similar to the 811/811-A.

The RK-31 has a slightly heavier filament @ 3 amps, while the TZ-40 runs the same voltage at 2.5 amps.

http://www.tubecollector.org/tz40.htm

Well, TZ-40's are easier to come by, have not thought about using those, might do so now.  I think some of the old Globe King 400's used these as I remember seeing that stamped on the chassis somewhere.   Thanks Don, would like to work you soon, have heard your booming homebrew up here in Cincinnati many times...but for now...I am iced up but good.

PS> Pic is HB yagi-moxon for 20, 17,15,10M ... only the 20 meter element is directly fed, the others are slaved to the DE...for some reason it has a good SWR on 40 as well, good back up antenna.

73, .Tim

I'm with Don, especially since you got the Glob Queen percolating. It sure would be cool to get the thing back as close to its original configuration as possible, considering the quality of construction and provenance of the rig. I have a stash of old Raytheon stuff, but it's buried up atm. Was out there moving stuff today to get to some meters, so if you're not in a hurry and decide to definitely go that route, drop me a note via email.

You might be able to find some OTs in your area who could offer ideas as to the tuning unit and speech amp. Who knows, maybe someone will even remember the transmitter and have pics/details. Even if it's not identical, it would sure be a lot more interesting historically.

And when you get a chance, post some shots of the WRL transmitters. Always loved the ones with the bakelite meter bezels, think it was the 500B or C that went to the clear plastic.