RCA cabient from scratch and help needed on the next steps

Posted: 12/14/2005 4:57:56 PM
echoplex

From: Boulder, Colorado

Joined: 8/17/2005

Mark (Dayfan),
I looked at your drawings before, but now the links don't work for me:
members.tde.com/mmckeown/Theremin/ThereminDwg1.jpg
members.tde.com/mmckeown/Theremin/ThereminDwg2.jpg
members.tde.com/mmckeown/Theremin/ThereminDwg3.jpg
Could you possibly post these again, or email to me? They looked like very detailed drawings.
You did a great job on your restoration.
echoplex at yahoo.com

Mike, I really like what I see of your cabinet. I have an RCA theremin (maunette, restoration article featured on thereminvox http://www.thereminvox.com/article/articleview/159) whose cabinet was destroyed long before I bought the chassis/power supply/coils. I have a cabinet that is similar to the RCA, but not an exact copy.

If either of you, Mark or Mike, has any interest in building a cabinet for me, or selling me some cut wood for me to assemble, or sending me drawings, I'd love to hear from you.
bret in boulder
Posted: 12/16/2005 4:32:58 PM
Dayfan

Joined: 10/8/2005

Echoplex,

I don't know why the links didn't work. I reposted the links under a new topic so try again. If you still have trouble let me know and I will email them to you. Sorry, but cabinet work is not fun for me. You might see if anybody else is interested in a cabinet and get a volume discount at a cabinet shop.

Mark
Posted: 12/16/2005 4:57:01 PM
echoplex

From: Boulder, Colorado

Joined: 8/17/2005

Mark,
Thanks for the reply. I got the links to work again. Great drawings.

I am impressed with your restoration of the RCA that you did. Did you repaint the chassis, the paint looks so good?

If so, what paint matches the original rca brown?

bret
Posted: 12/16/2005 5:39:27 PM
Dayfan

Joined: 10/8/2005

Bret,

Yes, I repainted both chassis and transformers. They were seriously rusted so I CAREFULLY sanded, primered with red primer and painted with Rustoleum leather brown enamel. This color is very close to the original. Masking everything and painting with the power cable attached is a challenge. I made cardboard plugs for the tube socket holes and removed as many screws as I safely could. I wrapped the power cable in a piece of gauze from my first aid kit to protect it. All pretty tedious but worth it.

Glad the links worked.

Mark
Posted: 12/16/2005 6:06:55 PM
echoplex

From: Boulder, Colorado

Joined: 8/17/2005

Thanks for the paint information.
Talk about seriously rusted, my rca was so water damaged that the cabinet was gone (why I need a replica cabinet). The chassis are pitted with rust.

I have put off sanding and painting the chassis, but will need to do this eventually. I don't even think about removing the components to repaint it.

If you have found any good websites describing the process of restoring and painting a rusted chassis, I would be grateful.
bret
Posted: 12/17/2005 11:55:42 AM
Dayfan

Joined: 10/8/2005

Bret,

How rusty is the inside of the chassis? The outside rust pits can be repaired with bondo or equivalent, then primered and painted. Just like auto restoration work. If the inside is rusty but the electronics function I would scrape as much rust off as possible and not worry about it because you have to weigh the chances of damage to the old components against what you gain. You could seal the inside with some clear varnish. As a last resort you could find a Radiola 17,18, or 60 radio and use the chassis. I think one of those is the same or very close to the RCA, some adaptation might be necessary. This is a last resort move. The power supply for the Radiola 60 is identical to the RCA so you could just replace the bad one.

Mark
Posted: 1/14/2006 8:27:03 PM
Jason

From: Sammamish, Washington

Joined: 2/13/2005

I finally tracked down an e-mail address for Floyd Engels: FEngels07@cs.com
Posted: 6/20/2006 1:15:46 PM
mikebuffington

From: AZ

Joined: 11/25/2005

More RCA replica progress!

To Dayfan, and others who are interested:

I got an RCA Radiola 60 last night and took some photos:
http://bedsidestory.livejournal.com/31555.html

Of course, questions arise.

Mark, The Radiola's power supply has a cable for the faceplate light and the power switch that do not appear in the theremin service notes. What do I do about those? Just leave them or should I remove them? I can't really follow where they lead into the power supply and figure there's no need to mess with them. Any thoughts?

The small coils that I hope to use for the volume, fixed pitch, and variable pitch coils are 1.5 inches in diameter instead of 1.75. Without being able to measure the values of these coils, can you tell me what the difference is?

There was a heavy white paper that was under the power supply, probably used to protect it and keep it dry. Are these in the 1264 theremins?

Is there a Radiola 60 service manual like the theremin's? That might be helpful for a neophyte like me.

Also, I can't quite wrap my brain around this, but: the audio outputs are on the power supply? How does this work? I guess it's possible, but it doesn't make sense to me.

Unrelated to the radio, I was wondering if anyone has the volume, pitch and on/off and off/play faceplates that they could cast a mold for me? I saw on Chuck's ebay listing that some would be difficult to find. Anyone willing to make a mold of their RCA theremin's plates??? I know you want to!
Posted: 7/4/2006 10:30:20 AM
Dayfan

Joined: 10/8/2005

BM,

The Radiola's power supply has a cable for the faceplate light and the power switch that do not appear in the theremin service notes. What do I do about those?

*I would follow the dial light wires into the power supply and cut them off or just cut the socket off and tape the ends of the wires. The power switch the same except you could use it to turn the power on/off if you wanted to.

Just leave them or should I remove them? I can't really follow where they lead into the power supply and figure there's no need to mess with them. Any thoughts?

The small coils that I hope to use for the volume, fixed pitch, and variable pitch coils are 1.5 inches in diameter instead of 1.75. Without being able to measure the values of these coils, can you tell me what the difference is?

*I had the same thought but decided to make new coils. You can remove all the hardware from the coils and use to make new ones. Unfortunately the difference in diameter makes a big difference in inductance. Send me the coil diameter and length and I will calculate an equivalent inductance coil for you. It would be useful to come up with an equivalent coil.

There was a heavy white paper that was under the power supply, probably used to protect it and keep it dry. Are these in the 1264 theremins?

*The "paper" is actually asbestos so don't eat or inhale it although it probably won't hurt you. It is to protect the cabinet from heat. Not really necessary or used in a RCA.

Is there a Radiola 60 service manual like the theremin's? That might be helpful for a neophyte like me.

*I could only find a schematic. If you need it email me at mmckeown@hughes.net.

Also, I can't quite wrap my brain around this, but: the audio outputs are on the power supply? How does this work? I guess it's possible, but it doesn't make sense to me.

*In our modern world it doesn't make sense because we all are used to low impedance outputs from a transformer. Back in the 1920's speakers were high impedance and the high voltage from the plate part of the audio amplifier circuit went through the headphones or speaker coil. Because the high voltage comes from the power supply, it was just as easy to have the audio output there. Look at the RCA schematic and you will see this.

Unrelated to the radio, I was wondering if anyone has the volume, pitch and on/off and off/play faceplates that they could cast a mold for me? I saw on Chuck's ebay listing that some would be difficult to find. Anyone willing to make a mold of their RCA theremin's plates??? I know you want to!

*The on/off can be found but not easily. The off/play is impossible. Making molds would be easy and non destructive. Good idea!

Mark
Posted: 7/4/2006 8:17:24 PM
mikebuffington

From: AZ

Joined: 11/25/2005

Mark,

Thanks for the info. I did find the schematic of the 60 online. Looks like Radiolaguy sells nice reproductions of the service notes, but I don't know if it's worth it for this.

I can see where the light's wires go, and will probably cut them. For the power switch, I think I will separate the two splices, remove the switch, re-splice them.

I have looked closer at the SPU of my Radiola 60 and see more differences from the Theremin's SPU.

On the Radiola SPU, terminal 5 (green w/ red chaser wire) goes to one of the output jacks, and the other (green) comes from one of the "filter reactor and filter condenser connections." The Theremin service notes show terminal 2 (red wire) connecting to the first output and a red wire coming from a different "filter reactor and filter condenser connection" going to the second.There also appears there should be a 0.02 MFD fixed condenser bridging the two outputs that I don't see on my Radiola 60 SPU.

Also, the connections to the "center-trapped resistors" don't seem to be the same. The center connections of the two are bridged by a black cloth wire. It's getting hard to follow because I'm jumping back and forth between 2 schematics, figure 7 of the manual, and my SPU. Plus these 78 year old wires don't look like they should any more. I can see some color still, though. I bet these things looked really beautiful right from the factory.

i can see how bridging terminals 6&7 and 3&4 might override some of these differences, but I'm still confused about the output jacks with terminals 2 and 5 (plus terminal 1 according to the Radiola schematic.).

Glad to know that paper is actually asbestos! It's been bagged and tagged now!

The Radiola 60 coils:
thickness: 1/16
diameter: 1+1/2
lengths (the longer one is the one that sits horizontally): 1+13/16, 1+19/32, 1+10/16

Thanks Mark,

Mike

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