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 Post subject: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Aug Fri 25, 2017 4:06 pm 
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Location: Monroe, NC 28112 USA
In moving stuff at the AWA Museum into new storage they unearthed an interesting relic now near 'death'.
It is a development version of the first AC powered superhet made by GE. Nothing like it made it into production. The bottom of the cabinet has no salvageable wood but there are enough clues to reproduce an exact replica. The sides of the cabinet broke off in pieces and what is shown is the 'best side'. Inside veneers are loose with half of them completely detached. I think I can glue them back in place. The top lid is complete and not warped but is severely gouged here and there.

The goal is to document the design configuration and compare to production examples. Then make the cabinet and chassis parts look fairly OK such that a viewer is not drawn away from study of the designers' intent OR to focus on what was done to make it presentable.

This is going to make my rebuild of the Zenith 3R earlier this year look like a piece of cake. http://kd4hsh.homestead.com/zenith-3r-00.html

Wish me luck.

Robert

Robert


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Aug Sat 26, 2017 4:43 am 
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Robert,

Interesting.

This looks like a project to re-package a Radiola 25 with the loop and an AC supply enclosed to create a table model. I wonder what the SPU is? Possibly the RCA conversion unit for the 25 to AC...

Chas


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Aug Sat 26, 2017 3:25 pm 
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Location: Monroe, NC 28112 USA
SPU ??? Don't know that abbreviation...

I looked through the Red Book and on the first pass I cannot see receiver modules that match what I'm seeing in this outfit. Ditto on looking through the RCA Service Notes and replacement parts pamphlets (with their much better photos). I sort-of think this predates the Radiola 25 and 28. Still much poking around with Ohm meter after extensive clean-up.

Robert


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Aug Sun 27, 2017 4:41 am 
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Posts: 5118
Location: Radio Heaven, North Carolina, near Charlotte, 28106-3015
wow, such sad condition, it's much worse than it was described to me when
they first found it.
I can't imagine how you're going to save that.
Are you going to try to preserve it, what about replacing the missing
wood, are you going to make it look old?
I think maybe make all the replaced wood look very different so it's
clear to anyone looking at it that it's replaced and is just there to show
what it should look like.
It's clearly not of the vintage of the original super-het, don't know
that I've ever seen a front panel that looks like that.
The tiny loop antenna looks silly, don't look like it's big enough to
do anything, compare it to the super-het loop...

Good luck, it'll be interesting to see what you do with it.

_________________
73, Ron w4ron
http://radioheaven.homestead.com/menu.html


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Aug Sun 27, 2017 4:53 am 
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Location: The Old Dominion VA 23518
Robert Lozier wrote:
SPU ??? Don't know that abbreviation...

I looked through the Red Book and on the first pass I cannot see receiver modules that match what I'm seeing in this outfit. Ditto on looking through the RCA Service Notes and replacement parts pamphlets (with their much better photos). I sort-of think this predates the Radiola 25 and 28. Still much poking around with Ohm meter after extensive clean-up.

Robert


Socket Power Unit
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_________________
Brian
"Capacitor Cosmetologist since 1979"
USN Retired 1984-2006 (Avionics/Cal)


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Aug Tue 29, 2017 2:11 am 
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Joined: Jul Mon 21, 2008 1:00 pm
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Location: Grantham, New Hampshire
Can you provide a picture from the top? I'd be interested in seeing the overall layout??


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Aug Tue 29, 2017 7:58 am 
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Location: Port Orchard, Wa
Robert, after seeing the Zenith 3R presentation, I know if any one can save this GE

prototype, it is you. You are the master!


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Aug Tue 29, 2017 1:19 pm 
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Location: Monroe, NC 28112 USA
JBL_1

Not exactly the view you asked for but the best of the 100+ taken to date. I'm always frustrated in getting stuff back together. There is always at least one questionable item that seems to have escaped the camera lens.

To clean the two tuning condensers yesterday burned a good 7 hours. The power supply block is almost done after 15 hours or so.

Today I hope to get the angle iron base and the catacomb chassis free so they can be sand blasted. Too bad just for using a wire brush. Will have to fill with body putty here and there.

Fun???

Robert


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Aug Tue 29, 2017 4:25 pm 
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Robert,

Does look an 8 tube catacomb, not the 6-tube as I had stated above. However, there is usually a tuned antenna stage for the 8-tube. Possibly part of the development process. I wonder if there are "RCA" lead seals on the cat?

For the Radiola 28 AC and 30, there should be a bus bar strip on a series of screwed lugs at the upper rear edge of the cat. The purpose is to place all the filaments in series and provide bias in the form of resistance wire wound on the strip. For the DC version of the 8 tube cat there is a strip to place all the filaments in parallel. It is the external strips that determine the catacomb to be AC or DC as defined by RCA. That may not hold true for this prototype.

Judging by the state of corrosion I suspect if there are windings on that bus-bar strip they may be eroded.

GE may have altered this strip for this "un-tuned RF" model. So resistances and jumpers may not hold true.

In my repairs of cats I have found that this lug, screw, strip to be a source of noises and had to throughly clean all the lugs and replace the screws. Any rivet connections were soldered.

BTW audio transformers inside are 3:1, same lamination size and windings as a Radiola III, 20, 24, 25, 26 and 30 cats. Laminations are drilled to fasten to a bracket within the cat. Other transformers may not have the holes in the laminations.

I have an extra pair or Radiola 25 tuning capacitors and dial drums should there be an unrecoverable fault with the ones in this example. I am making a wild assumption they will drop-in fit, well, maybe...

Chas


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Aug Tue 29, 2017 4:56 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1517
Location: Monroe, NC 28112 USA
No lead seals but suspicious outlines to suggest they were there at some point.

The catacomb is for 8 tubes but there are no pins in the 8th socket.

Have not addressed the actual circuit yet... The PS (SPU) with its three sockets leave me to suspect that it might have had two UX-216s and a UX-210? Since the full wave UX-213 was not announced until Sept 1925 and reported not to have been used in any radios... Only battery eliminators. Too early for the UX-271A for the power tube...

Robert


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Aug Thu 31, 2017 7:50 pm 
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Hi Robert, I can see that I approached the right guy to tackle this momentous job.

We have searched our database and can not find the source of the donation for this historic piece. It just appeared in a box under a table, found while moving the annex to its new home. It would be great to find out how it made its way to the AWA collection.

Have you ever seen the spiral rheostats used in any other RCA products?

After viewing the magic you performed on the Zenith 3R - I was in awe of your expertise- it took a lot of patience & perseverance.
Your attention to detail & knowledge of the steps involved in reproducing the missing & broken parts took it to a whole new level.

Thank you again for undertaking the job of bringing this early RCA Prototype back to displayable condition. :D

73 Jim


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Sep Tue 05, 2017 4:55 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Monroe, NC 28112 USA
I guess why I love this hobby of restoration, conservation and historical research is because, if you care to, you can be exposed to an almost infinite set of challenges new to you or me.

One challenge on this set is that the braided jacket cable from the power supply to the catacomb fanning strip is completely missing over 90% of the major diameter of the cable. The braiding is ragged on both ends assuring me that the jacket was indeed removed by insects or mice. Also you can go through all the RCA service notes and see that cable bundles from point A to B all have an over braid. Interesting in that the cable must have had the braid removed recently because the exposed wires are in pristine condition.

How the heck to replace the braid.?. No getting away with wrapping with Scotch 33 or friction tape or just wrapping with embroidery floss like I do on short breaks in headphone and speaker cords... YouTube has a number of videos showing how cable bundle over-braid machines work. Too complicated! The cable bundle would be too damaged if I tried to unwire it and send it out to one of the couple places left that make reproduction cable harnesses for antique cars. (Probably too expensive anyway for a one-shot setup.)

So I came up with this contraption and it WORKS! Well at least well enough so that people will probably not suspect that the braid has been replaced. (The forger's goal :D ) The major problem with this is that there is no way to control thread tension... After four layers of new braid are added, you stop and pull everything tight. What you see are four hours of actual braiding... Another two or three hours will have the task done. (None too soon for me.) But it is an interesting challenge for my skill level and shop resources.

Robert


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Sep Thu 07, 2017 1:52 am 
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Location: Grantham, New Hampshire
I've wanted to make or have made those very harnesses for my RCAs and Victor's with RCA's. What a neat idea on how to achieve it. A long time ago I saw a table radio that said RCA Radiola 28 but was clearly a totally different set using UX-201As. I also owned a prototype Radiola 18 that had the same GE engineering department tag. That would have been around 1927. The dial escutcheons were actually cast and not stamped and did not have the writing. I sold that one about 10 years ago but wish I had kept that one. I wonder the one you are working on is really a prototype or something else?? Maybe a model for RCA licensing to demonstrate RCA patents or complete radio outfits to Victor and Brunswick. It looks to far along to be prototype?? Nothing ever appeared in production that is similar.


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Sep Thu 07, 2017 2:13 am 
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Location: Monroe, NC 28112 USA
JBL_1 Interesting thoughts on why this set might have been made. I'll add them to the narrative on this project.

Today I was starting to clean the drum shaped loop antenna. Note that there is a blob of what looks like trash stuck to some of the loop wires. It is some sort of an insect nest and guess what it is primarily made of? It is the missing braided jacket chewed up almost to the consistency of very fine wet dryer lint :shock:

Robert


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Sep Sun 10, 2017 3:45 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Monroe, NC 28112 USA
Latest challenge... The base of the cabinet is useless... All new wood required.... The snag for me is that I cannot find the correct molding router bit profile in any on-line reference.... I received a quotation on a custom bit. $158 + $15 shipping... I suspected it would not be cheap... I'm going to hold off until I prove that I can do a credible refinish on the rest of the cabinet... If it comes out looking pretty bad, I might just go with a stock profile and report the differences.

If you think that this profile cut looks pretty good, know that it is heavily Photoshopped.

Robert


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Oct Sun 29, 2017 4:32 pm 
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Sort-of a mini update on this project. What a TIME PIT !

The outside walnut veneers on most all the panels of the cabinet were loose on the edges and had to be glued and pressed. The inside veneers had to be steamed off. On one panel both layers had to come off the lumber core. On the others only one layer. Each veneer had to be bleached to kill the mold and washed to remove the bleach residue and the old hide glue, then treated with 'veneer relaxer', sandwiched between layers of blank news print and run through my old cast iron book press to squeeze out the water. After three changes of paper, the veneer is flat and can be placed in the press again for a day to dry completely.... Did I mention TIME PIT ???

When one layer was steamed off I found a powder post beetle gallery that I cleaned out and filled. I'm pretty confident that that infestation is old and now dead.

One of the inside veneer panels was not salvageable and I replaced it with a similar poplar core veneer. On the back side of the cabinet, there was one, maybe 7", section of the veneer completely missing. My poplar veneer would not match close enough if inserted between two sections of the old veneer. Fortunately there was enough core veneer in the trashed base for me to extract a 9" section that could be processed and act as a replacement that matches almost perfectly.

The top lid was awful but I wanted to not have to resort to veneer replacement... I have just not found new walnut veneers that come close to matching this old growth wood. I think it has come out good enough to not detract from the overall appearance of this old artifact.

The angle iron frame had to be sandblasted and filled with automotive glazing putty before I can start re-assembly. I should start on putting the catacomb and tuning parts back together in the next two weeks. The mystery power supply has been refinished but I need to do some detective work to figure out just what it is... The whole thing is potted in asphalt and I am NOT going to melt it down. Some ARF research turned up a thread where the late Doug Houston was commenting on why the early AC Radiolas did not have push-pull audio outputs. He thought there should have been an iteration where there would have been push-pull 71s and maybe a 213 rectifier. I hope to be able to determine what tubes would have been used in the three sockets on the PS module. So yes, I'll be putting juice on the tranny but only for detective work... With as much severe rust and wood delamination I'm positive ALL the paper caps in the PS block are dangerously leaky.

These photos were taken just after I had stained and put on a thin coat of lacquer to verify coloration. The base is finished EXCEPT for routing the edge. The bit profile is unlike anything available on the market today. I have found a shop that makes custom profile bits... $175 with shipping... Will cut an order this week...

Robert


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Oct Sun 29, 2017 6:42 pm 
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Location: Grand Island, NY USA
Robert,

WoW !!!!!!!!!!!! The cabinet looks beautiful!!!!!!!!! Just Incredible !!!!!!!!!!! WoW.

I was following your progress on the forum, but noticed that not many new entries had been made lately.

This one has me blown away.... Talk about a resurrection..... We will be keeping an eye on your progress,
and can assure you that your costs will be reimbursed- if it wasn't for you the radio would have spent eternity
in the old cardboard box.

I like your nickname for the set- Time Pit !!!

We will look for the lid prop on Tuesday & let you know what we come up with.

One quick question.... Are there 2 separate antennas or do they work in conjunction with each other?

Thank you so much again for your effort in bringing this piece back to what it originally looked like.

73 Jim


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Oct Sun 29, 2017 7:14 pm 
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Location: Monroe, NC 28112 USA
Jim,

I'm only 99.9% certain that the cross frame coil was the way to couple to an external antenna. :)

There are no signs of external connections for the drum antenna...

Robert


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Nov Thu 09, 2017 11:43 pm 
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Location: Monroe, NC 28112 USA
Well it was time to try and figure out just what the power supply unit does...

Three mystery tube sockets... I hoped the tranny was not open circuit.... No problem there... A careful dim bulb power-up to 110 VAC had it drawing less than 50 ma. with no tubes inserted. There are three 5 Volt center tapped windings. Two 460 Volt center tapped windings each connected to the center or right tube socket.

The only thing that makes sense is that there are TWO UX-213 rectifiers and a UX-71 audio output tube for the socket on the left. AIN'T THAT INNERESTING ! Current lore says that the UX-213 was only used in add-on 'B' eliminators and not for very long. Well, at least one GE radio used it. The 213 and the 80 have the same filament power requirements, so no problem to pop in 80s for some detective work.

One rectifier circuit provides about 250 Volts (no load) The other rectifier circuit provides 240 Volts with taps at 150, 85 and 37 Volts (no load).

Why two UX-213's ? The UX-213 could only supply 65 ma. and that was not enough to run the circuit. (The UX-280 was apparently not available at the time of the design.) So.. Put two to work.

The Radiola 28, 30, etc. used the UX-210 power tube but it has a 7.5 Volt filament.... This Engineering prototype circuit has just 5 Volts to service the audio output tube. The UX-71 is the only power tube in the RCA pipeline that would run on 5 Volts.

So if we could find out when the first UX-71 and UX-280 tubes were released for design/production use, we could use that as a pretty good marker as to when this radio was built.

Figuring out how these circuits were used to light the filaments of the UX-199s is a whole 'nuther thang. Trying to rationalize the readings I'm getting with a VOM to the published Radiola catacomb drawings have me cross eyed.
Right now I'm going to quit that line of investigation. The PSU and the catacomb are both potted and I'm not going to melt-out 90 year old asphalt and beeswax potting compounds and break up brittle insulation for the answer.

I'm waiting for my $173 custom router bit to be fabricated so I can finish the base... But there are plenty of odds & ends to be done and condense the restoration/conservation narrative into a manageable format.

Robert


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 Post subject: Re: GE Radio Engineering Department Receiver Section 1925?
PostPosted: Nov Fri 10, 2017 10:46 am 
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Location: England
Amazing job, really well done.

Gary


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