A giant is coming home.

Discussion in 'Amplitude Modulation' started by N6YW, Sep 24, 2019.

ad: L-HROutlet
ad: l-rl
ad: Left-3
ad: L-MFJ
ad: abrind-2
ad: Left-2
ad: Subscribe
  1. K5UJ

    K5UJ Ham Member QRZ Page

    The transformers RCA made for that rig are robust, judging by the mod. transformer and reactor. It's kind of unconventional to bolt them to the front of the cabinet instead of the bottom but that let them use a cabinet that isn't very deep. I am guessing the bolt holes are tapped so no nuts are needed on the other side. The iron on the right (the mod. transformer, reactor and what looks like a filter choke) can probably be removed by one man unscrewing the final upper bolt with one hand and easing the iron down to the one just below it or the bottom. The plate supply transformer is tougher--looks to weigh around 100 lbs or so. May never need to be removed but if so, there are three ways: two guys one holding the other unscrewing, one guy and a chain or cable to hold the iron, or tipping the whole box forward onto a blanket so front is now the bottom. Observe that the front panel knobs are recessed. There was a reason for that apart from looks. I'll bet when that rig was assembled at RCA, the box laid on its front on a mat on top of a roller conveyor and they set the iron in and bolted it down. The rig was probably assembled with the cabinet being one big tray.
    N6YW likes this.
  2. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    From the looks of it, the inner chassis was lowered into the “shell” as there are fly-rigging holes in the top where you might see some 1” inch bolts in the pictures. Those are stud shackles we inserted to allow the use of “Crosby” U shackles and span sets, or nylon rigging straps. I don’t want to confuse those of you who don’t know rigging hardware and terms.
    The outer shell is quite heavy duty itself and it resembles a sarcophagus in a way.
    I am worn out from the exercise needed to ready this transmitter for commissioning. It will be my last Heavy Metal transmitter acquisition. I have all I need and when the time comes to get another transmitter, it will be solid state.
    K0UO likes this.
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    Thank God they do not make them like that anymore. Makes my back hurt thinking about it. Now if they could have just make it look more like a Wurlitzer 1015 Bubbler Jukebox would be cool.


    OK time to be serious. CONGRATS, nice rig.
  4. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    I have seen photos of the older RCA 1 kW transmitters that used triodes (204-As and later 833-As). They mounted the mod iron the same way. The BTA-1R that I parted out was missing the modulation transformer, but the plate xfmr and mod reactor were mounted on the floor of the cabinet, and as I recall, the empty space for the mod xfmr was on the floor as well.

    A safer way to remove and replace wall-mounted iron, assuming the holes are tapped and no nut is used, would be:

    1. First, disconnect all wiring to the transformer and remove two of the mounting bolts.
    2. Find a couple of scrap bolts or screws the same size as the mounting bolts and the same thread pitch, long enough to go through the mounting holes on the xfmr and wall of the cabinet, and extend at least 1½ inches or so outwards when screwed completely through the wall panel. Grind or cut off the heads, and using a hacksaw, fabricate a screw slot at the end where the head was cut off. Make sure an appropriate screwdriver will fit into the slots. If it was a slotted screw, you need only to grind the sides of the head down to the same same diameter as the body of a screw, leaving something like a setscrew, and use the original screwdriver slot.
    3. Insert the modified bolts into the holes where the original mounting bolts were removed. Screw deeply enough into the wall of the cabinet that the threaded rod goes all the way through the sheet metal.
    4. Now, remove the other two original bolts/screws holding the transformer in place, carefully leaving the transformer "hanging" in place on the studs formed by the modified bolts. Be careful, make sure it balances well enough to stay on the studs and doesn't try to tilt or roll off.
    5. Preferably with an assistant, firmly grasp the monster transformer, slide it off the studs, carefully remove it from the cabinet and set it on the floor. Leave the slotted studs in place.
    6. Reverse the above procedure to re-mount the transformer.
    K5UJ likes this.
  5. W0RIO

    W0RIO Ham Member QRZ Page

    Jukeboxes really took art deco to the extreme, here are a couple of examples I grabbed from Craigs List ads.
    Have fun with that "new" transmitter.

    1941Wurlitzer850.png RockOlaJuke.png
    K0UO likes this.
  6. KA2CZU

    KA2CZU XML Subscriber QRZ Page

    thank you for this thread!

    you have the knowledge, energy and will, to pull off something I only dreamed about years ago, and never did!

    so, for those in my shoes, thank you for the great thread/pictures and of course, giving big iron like this a new home!
    N6YW likes this.
  7. K5UJ

    K5UJ Ham Member QRZ Page

    I keep forgetting about making those threaded pegs. Of course the idea for hanging rack chassis can apply to these transformers.

    it looks like that rig uses p.p. 828 RF drivers? the 828 is remarkably similar to the 804. I've also always wondered why the 806 seems so scarce. It has always looked like a hell of a tube. http://www.nj7p.org/Manuals/PDFs/Tubes/RCA-gfat-1942.pdf I've never seen anything that ran 806s.
  8. W7TFO

    W7TFO Platinum Subscriber Platinum Subscriber QRZ Page

    In that BTA- series the big iron is mounted on studs. Held on with washers & nuts.

    Still quite a chore to remove/replace, as the area is cramped and they have lots of sharp angle iron. Very easy to shed a bit of blood just working a tool in there.

  9. W0RIO

    W0RIO Ham Member QRZ Page

    I have a personal "rule": if I ever get cut by a sharp edge, I take a fine gauge file and/or sand paper and round the edge.
    Electronics of all types have sharp edges, as do wood objects and even plastics such as refrigerator trays.
    I shed a lot less blood that way, plus it's a good way to "get even" with the object that just sliced my skin ;-) ^&@#!
    N6YW likes this.
  10. W2VW

    W2VW XML Subscriber QRZ Page

    I picked up an RCA 1D and the 250 driver/nighttime tx back in 1991 from WHLD near Buffalo.

    Some stuff had been removed but all the 1D iron was still there.

    Station logbooks indicated the transmitters were in service in 1937 and removed from service in 1967.

    Iron was mounted on studs and I was able to remove it by myself. Today I would rig the mod, reactor and plate iron : (

    I am currently using the autoxfmr and mod reactor on the air.

Share This Page