Old transmitter Rescued from the Scrapyard
K1JJ:
Quote from: WD5JKO on March 22, 2020, 08:18:30 AM
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I figure about 1250V B+ and 200W DC input to the RF stage.
Jim Wd5JKO
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They sure worked mighty hard to get ~160 watts out in those days! Running 1/4, 1/2 or a full gallon really meant something back then.
Are the chassis' made of galvanized steel or are they aluminum... or something else?
T
Opcom:
Wow good job!
Junk yard rescues forever!
Opcom:
Is the HDVL coil set the largest "kw-sized" one? I may have some of that stuff here, if you are going to restore it, and it should be restored, but shipping would be quite delayed for reasons.
KD2AZI:
Gents, thank you. Have no fear, I saved it for a reason! The decks are from the Top:
PA
3E29 amplifier
PS + audio amplifier
Huge PS + Modulator
PS (with the loose iron)
The only thing missing on this unit (besides some coils) is an oscillator.
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3E29 tube is your IPA or intermediate power amplifier
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So the external VFO would feed this. Is the 3E29 a bold choice for that time? I read in the data that the tube has a 15 watt capability - so makes me wonder what kind of VFO he had.
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OM who built this decided to recess mount the panel mater(s)
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n
All the meters are recessed and I was wondering the reason for that. The downside it's it's difficult to read them with the screen in the way :)
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Did those transformers shown separately come from this rig?
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The loose iron was removed from the bottom deck and I guess the scrapper forgot to grab them - lucky me!
Yes, the final tank is HDVL, and I have some laying around, I think for 10m, 80m and maybe 40m.
I drew the diagram out for the modulator, and it really helped finding a 1940s Thordarson transmitter guide from Bunker of Doom website. The modulator tubes I have to figure out, guessing something in the 8xx numbering due to the length of the plate leads and the bases.
Here are pictures of the bottom side of the PA unit, and the top view of the PS/Modulator. The modulator transformers are UTC VM-4 and S-9, and that's great because there's plenty of docs available on the "VariMatch" transformers. The tube pictured is a 242 I stuck in there just to figure out what bases those are.
The chassis are all steel.
Looks like I have a good project. Not much rust, plenty of mouse crap and dust...really great shape! I just need to figure out the interconnections, then we'll start working on it...and the biggest piece I have so source is an oscillator - maybe it's time to look for one of those Millen jobs (?)
Thanks all for the comments.
W2PFY:
Quote
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3E29 tube is your IPA or intermediate power amplifier
So the external VFO would feed this. Is the 3E29 a bold choice for that time? I read in the data that the tube has a 15 watt capability - so makes me wonder what kind of VFO he had.
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My guess is that the original tube was more likely an 829B tube that looks identical but has more plate dissipation than the 3E29. The 3E29 was a WW2 radar & radar jammer tube whereas the 829B was always an RF or audio tube depending on its application. Your rig looks like a late thirty's or very early forties build so if a 3E29 would have been original, I would have thought that some of the parts and practices would been reflective of late forties or very early fifties workmanship. Just my opinion, but it may sound convincing on the Antiques Radio show? If nothing else, now you know that an 829B will work in there and if you ever need either tube, I have them around here somewhere.
BTW, if you can measure your modulator filament voltage, that would go a long way to figure out what tubes may have been in use there.