I'm in the really OLD radio and SET clubs now.

radio, tape, stands and accessories
Coffee Phil
vinyl addict
vinyl addict
United States of America
Posts: 5772
Joined: 20 Sep 2008 08:22
Location: California

I'm in the really OLD radio and SET clubs now.

Post by Coffee Phil » 03 Apr 2016 18:46

A few days ago I saw this radio at the Snowline Hospice thrift store:

[img]35009[img][/img]

It is an RCA Radiola 17. ~circa1927

They said everything would be one half price Saturday so got there when the store opened and got this radio for $25.

As expected there was a label saying that it was untested and as is. The power cord had been cut off and it lacks the external moving iron speaker.

Here is a view into the top showing the tubes:

[img]35010[/img]


I was able to find info on line including a schemo. This apparently was RCA's first radio designed from the start to operate from the AC power mains.

Starting from the left in the picture on the separate power supply chassis is the type 80 rectifier. Moving to the right are three type 26 directly heated triodes as RF amplifiers. Following the RF stages is the type 27 indirectly heated triode as the grid leak detector. After the detector is one more #26 as the first audio amplifier stage which is transformer coupled to the audio output stage which is a type 71A directly heated triode in the SET configuration.

The tubes were in random positions. I first got that sorted then decided to live on the edge and pulled the 80 rectifier and hooked a suicide cord to what was left of the power cord to see what I had. Some of the tubes started to light dimly. After wiggling the tubes to burnish the contact all but one 26 lit. Sadly it has an open filament. Sad, as I like the blue glass and old style shape.

Here is the dearly departed 26:

[img]35011[/img]

One aspect of the design makes me as an old radio engineer want to smack sense into the designer is that the signal passes from the antenna through the volume potentiometer to the grid of the first tube with NO preselection whatever.
The engineer in me wants to start hacking but the purest in me says leave it be.

Phil

vinyl master
vinyl engineer
vinyl engineer
United States of America
Posts: 20207
Joined: 01 Nov 2013 05:27

Re: I'm in the really OLD radio and SET clubs now.

Post by vinyl master » 04 Apr 2016 04:51

She's a beauty there, Phil! It makes me wonder what my man, Chris, would do...I think our new member Radiotiques had some really old ones like that in his radio room. Keep in mind that for $25.00, it might look nice all cleaned up, at least on the cabinet... :-k

Keep this guy in mind, too...

http://www.simonsvrr.com/cabinets.html

And a few more places to check out...

http://www.californiahistoricalradio.co ... directory/

Of course, our man, Radiotiques, does some restoration work, too, from the looks of things...

http://www.radiotiques.com/services.asp?Tab=Restoration

She's worth a nice restoration, don't you think? :-k

Coffee Phil
vinyl addict
vinyl addict
United States of America
Posts: 5772
Joined: 20 Sep 2008 08:22
Location: California

Re: I'm in the really OLD radio and SET clubs now.

Post by Coffee Phil » 04 Apr 2016 07:30

Hi Vinyl Master,

Thanks for the links. I found a cabinet restorer in Sonora in there. That is not out of the question to drive to.

I want to get this radio working before I worry over the cabinet.

It turns out it is getting interesting. The front of the cabinet says Radiola 17 and that is what I thought I had. Today I disassembled it and blew out the dirt and dead sow-bugs and compared it to literature which I had down loaded. There was a bunch of stuff which didn't match. Mainly the stuff to prevent oscillation in the RF stages (more on that in a bit) and the audio output transformer is not on the radio chassis but rather appears to be on the power supply chassis. The radio appears to be the very similar Radiola 18.

OK, about the TRF stages. It turns out it is a pretty good trick to make a tuned RF stage with triode vacuum tubes that won't oscillate. A guy named Hazeltine invented a neutralizing circuit which did just that and formed a company named Neutrodyne which licenced that intellectual property. Well RCA wasn't about to pay royalties so they came up with a way to run wires so the stray capacitance between them did Hazeltine's trick in a clandestine manner. Hazeltine figured out what they were up to and sued them. RCA stopped doing it and added series resistors in the grid circuit. I think Atwater Kent did that in some of their radios as well. It turned out that the Radiola 17 resistor thing didn't work all that well and it was an unstable, oscillatory POC. RCA then replaced the Radiola 17 with the similar Radiola 18 which had Hazeltines circuit. I'm not sure if Sarnoff paid them or used some other slippery trick.

It is amazing what you can learn in one day off the internet.

It appears that whatever I just bought, it came from an interesting time in radio history.

Phil

vinyl master wrote:She's a beauty there, Phil! It makes me wonder what my man, Chris, would do...I think our new member Radiotiques had some really old ones like that in his radio room. Keep in mind that for $25.00, it might look nice all cleaned up, at least on the cabinet... :-k

Keep this guy in mind, too...

http://www.simonsvrr.com/cabinets.html

And a few more places to check out...

http://www.californiahistoricalradio.co ... directory/

Of course, our man, Radiotiques, does some restoration work, too, from the looks of things...

http://www.radiotiques.com/services.asp?Tab=Restoration

She's worth a nice restoration, don't you think? :-k

spittenkittens
long player
long player
Posts: 1778
Joined: 23 Jun 2013 05:23

Re: I'm in the really OLD radio and SET clubs now.

Post by spittenkittens » 06 Apr 2016 00:46

I love that old stuff. And it shows how getting from there to now(learning and technology)is a process. To bad about the old tube, I bet there is another out there somewhere just waiting to glow again. :D

Melos Antropon
senior member
senior member
Posts: 488
Joined: 02 Feb 2016 04:31
Location: SW Michigan

Re: I'm in the really OLD radio and SET clubs now.

Post by Melos Antropon » 06 Apr 2016 01:15

Coffee Phil said: "It appears that whatever I just bought, it came from an interesting time in radio history"

Indeed. That was 1927. Ten short years later was 1937, and the most magnificent short and medium wave radio consoles ever built were in their heyday. It was a great time . . .

Tony

Big B5515
long player
long player
Posts: 1775
Joined: 04 Nov 2012 01:27
Location: West Virginia

Re: I'm in the really OLD radio and SET clubs now.

Post by Big B5515 » 06 Apr 2016 07:32

A very nice find for $25. Hope you can get it working again, and find a proper speaker for it. I was just debating sending the speaker in my 1931 Detrola out for a reconing and field coil rewinding ($150, ouch!). I still may have a few part changes to figure out from previous repair attempts such as output tube grid resistor, etc. (my radio does not match schematic either), but the 10K wire wound volume pot from Digikey seems to be holding up, and the 2 fresh #24 tubes cleared up sound quality considerably. This also revealed the improper mystery capacitor value with oscillation at less than full volume (apparently 2uf, not .2uf).

PS Checked my box of old style radio tubes, and have 1 blue glass #27, but unfortunately no #26 tubes.

Coffee Phil
vinyl addict
vinyl addict
United States of America
Posts: 5772
Joined: 20 Sep 2008 08:22
Location: California

Re: I'm in the really OLD radio and SET clubs now.

Post by Coffee Phil » 06 Apr 2016 08:03

Hi Big B,

Yes, I went and did it and the Airline is still sitting there. I just saw it and couldn't help myself. I did find a 26 in my stash which does light up so now all the tubes are lighting other than the 80 as I haven't powered it with it in place. I'll put some silicon diodes in it place and bring it up on a Variac. There are NO electrolytic caps in this radio as they were developed in ~1930 and this radio dates from ~1927. The power supply filter caps are just 1 microfarad and I'm assuming they are oil filled paper. PCB? The power supply filter relies heavily on inductors. Before electrolytics, microfarads were big and $pendy.

I am becoming convinced that the chassis is a Radiola 18. I saw a Radiola 18 dial escutcheon plate on eBay for ~ $13. I may bid on it so the cabinet matches the chassis. I am also watching a speaker for it. This radio takes a moving iron speaker which is high impedance driven directly from the SET output stage. I downloaded the data sheet for the 71a output triode. About the most beautiful triode curves I've seen, but wimpy. This tube is good for about 3/4 Watt at best. I get the idea those moving iron speakers are more efficient than the moving coils we know and love. Good thing with the low powered amp.

Phil

Big B5515 wrote:A nice find for $25. Hope you get it working, and find a proper speaker for it. I was just debating sending the speaker in my 1931 Detrola out for a reconing and field coil rewinding ($150, ouch!). I still may have a few part changes to figure out from previous repair attempts such as output tube grid resistor, etc. (my radio does not match schematic either), but the 10K wire wound volume pot from Digikey seems to be holding up, and the 2 fresh #24 tubes cleared up reception considerably.

PS Checked and have a blue glass #27, but no #26 tubes

spittenkittens
long player
long player
Posts: 1778
Joined: 23 Jun 2013 05:23

Re: I'm in the really OLD radio and SET clubs now.

Post by spittenkittens » 06 Apr 2016 23:47

Melos Antropon wrote:Coffee Phil said: "It appears that whatever I just bought, it came from an interesting time in radio history"

Indeed. That was 1927. Ten short years later was 1937, and the most magnificent short and medium wave radio consoles ever built were in their heyday. It was a great time . . .

Tony
I have a one of those, a 1930's with short wave, police and and broadband.. It has little jewel type colors that glow so you know band you are on. Plus it has a aux, 2 screws for a turntable etc. I can't pick am were I live and it does need some work. I The cabinet is in fair shape but I can't see who made it. But the speaker says Emerson on it. I looked it up years ago and it was the mid to late 30's.

Melos Antropon
senior member
senior member
Posts: 488
Joined: 02 Feb 2016 04:31
Location: SW Michigan

Re: I'm in the really OLD radio and SET clubs now.

Post by Melos Antropon » 07 Apr 2016 03:56

spittenkittens wrote:
Melos Antropon wrote:Coffee Phil said: "It appears that whatever I just bought, it came from an interesting time in radio history"

Indeed. That was 1927. Ten short years later was 1937, and the most magnificent short and medium wave radio consoles ever built were in their heyday. It was a great time . . .

Tony
I have a one of those, a 1930's with short wave, police and and broadband.. It has little jewel type colors that glow so you know band you are on. Plus it has a aux, 2 screws for a Turntable etc. I can't pick am were I live and it does need some work. I The cabinet is in fair shape but I can't see who made it. But the speaker says Emerson on it. I looked it up years ago and it was the mid to late 30's.
Mine was a 1938 Zenith, Spit, restored by my boyhood friend, and electrical wizard (we were both 15 at the time). When I was in college, my mom called one time, and asked if I wanted to keep it. 140 miles away, and caught up with my college affairs, I said (like a DAMNED FOOL): "No Ma, go ahead and trash it". There is an old Pennsylvania Dutch expression: "We grow too soon old, and too late smart". Ain't it the truth.

Tony

vinyl master
vinyl engineer
vinyl engineer
United States of America
Posts: 20207
Joined: 01 Nov 2013 05:27

Re: I'm in the really OLD radio and SET clubs now.

Post by vinyl master » 07 Apr 2016 05:02

Melos Antropon wrote: Mine was a 1938 Zenith, Spit, restored by my boyhood friend, and electrical wizard (we were both 15 at the time). When I was in college, my mom called one time, and asked if I wanted to keep it. 140 miles away, and caught up with my college affairs, I said (like a DAMNED FOOL): "No Ma, go ahead and trash it". There is an old Pennsylvania Dutch expression: "We grow too soon old, and too late smart". Ain't it the truth.

Tony
Do you ever long for another one, Tony? Or do you have something similar? You might have been "Too young dumb", but not anymore!

Melos Antropon
senior member
senior member
Posts: 488
Joined: 02 Feb 2016 04:31
Location: SW Michigan

Re: I'm in the really OLD radio and SET clubs now.

Post by Melos Antropon » 07 Apr 2016 05:47

There is an antique mall only 7 miles from me, VM, and there is an exhibitor there who specializes in restoring those old period beauties to mint condition, cabinet and all (his refinishing work is to die for, and I'm a good re-finisher myself!) But common sense rules, fortunately. I have a modern high-ticket "all band" communications receiver who's specs run circles around the SW specs of those old units, and the nearest worthwhile AM stations to where I live are in Chicago, which I can receive fine across the lake on my Henry Kloss Model 1. My Yamaha R-S500 receiver and home-made FM antenna give me excellent FM, which I do listen to a lot. I would, in effect, be spending $400 for "audio jewelry". Helps keep me on "sane" ground, but doesn't stop the drool when I look at them!

Tony

Big B5515
long player
long player
Posts: 1775
Joined: 04 Nov 2012 01:27
Location: West Virginia

Re: I'm in the really OLD radio and SET clubs now.

Post by Big B5515 » 07 Apr 2016 06:29

I know the feeling. I'm still upset with myself for not taking better care of my Fairbanks Morse model 58 (It was given to me around age 9 after I got it to work), then leaving it in harms way on a staircase half wall and disposing of its original damaged parts and speaker after a friend accidently knocked it off the edge. I began collecting and fixing a few radios last year, but none quite equal the good looks and sound quality I remembered from this radio that belonged to my great grandfather.

Coffee Phil
vinyl addict
vinyl addict
United States of America
Posts: 5772
Joined: 20 Sep 2008 08:22
Location: California

Re: I'm in the really OLD radio and SET clubs now.

Post by Coffee Phil » 08 Apr 2016 03:50

I just won this:

http://www.ebay.com/itm/252339510238?_t ... fresh=true

I do believe it is the correct speaker for the Radiola 18 (which I'm convinced mine is).

It is untested but the seller said it has no rips. I don't know if he mean just the grill cloth or the speaker cone as well. As I mentioned this speaker is not of the moving coil type we know and love. It is some form of moving iron, most likely a balanced armature type. Unless I really scored and it is in working order, I will have a new thing to learn. I'm pretty old but never have I had to deal with one of those old speakers before. These speakers are very high impedance. In the case of the Radiola 18 there is no output transformer. You SET fans will know there are two configurations of SETs. One with the output tube current passing through the transformer and the alternate approach with the current supplied with a choke and a coupling capacitor coupling the tube anode to the transformer primary. My radio is the latter but with NO output transformer. The anode of the 71A is coupled to the speaker via a 0.5 microfarad capacitor.

If necessary, I hope my reconeing guy can deal with it. I'm pretty sure I'm on my own with the balanced armature motor, but hopefully he can fit a cone.

Also the cord looks to have a 1/4" phone plug installed. That is not correct. It is supposed to have two separate pins like the earphones which I used with my crystal sets when I was a kid. I was in the Bay Area yesterday and looked at the electronics surplus stores which I frequent for some pins with no success. I may have to make my own from brass rod.

Phil

Big B5515
long player
long player
Posts: 1775
Joined: 04 Nov 2012 01:27
Location: West Virginia

Re: I'm in the really OLD radio and SET clubs now.

Post by Big B5515 » 08 Apr 2016 09:14

Another nice find for the price, I had seen a horn type radio speaker at an a local store that finally did sell for $150. Hopefully, it's still in working condition and just needs a little cleaning and TLC. I did locate this shop that specializes in rebuilding vintage speakers if needed, http://www.thespeakershop.com/ Pricy, but he's been doing speakers since 1973. I've got my speaker packed and ready to ship, after I give him a call tomorrow.

Coffee Phil
vinyl addict
vinyl addict
United States of America
Posts: 5772
Joined: 20 Sep 2008 08:22
Location: California

Re: I'm in the really OLD radio and SET clubs now.

Post by Coffee Phil » 08 Apr 2016 19:03

Hi Big B,

Thanks for the link. Now I'm pretty sure that guy can do my Radiola speaker. He showed one as a basket case which he disassembled, bead blasted, and rebuilt. I'm pretty sure my speaker guy can't do that. Now, I'm hoping I won't need him as I'm pretty sure the price will scare me. My Radiola speaker is slated to arrive on the 14th. I'll call him when I see mine and describe it. When I regain consciousness if the motor part looks OK or fixable by me I'll call my guy and ask about just fitting the cone.

I noticed your guy has an ElectroVoice 30W on his wall. Good to know someone does those still. I don't think Electrovoice will do them any more. Now that is a service which I hope I never need. I had mine reconed about 25 years ago by ElectroVoice and it cost me $500. A solid state amp screwed up and put DC into the voice coil. I am now paranoid and only use transformer coupled amps with it.

I think I have the solution to my speaker connector problem. I was looking at the test probes on my DVM and it hit me. I poked them into the speaker connectors on the radio and they fit fine. I'll just get a couple of probes and cut the plastic handles to ~ 1". It should look believable.

Phil

Big B5515 wrote:Another nice find for the price, I had seen a horn type radio speaker at an a local store that finally did sell for $150. Hopefully, it's still in working condition and just needs a little cleaning and TLC. I did locate this shop that specializes in rebuilding vintage speakers if needed, http://www.thespeakershop.com/ Pricy, but he's been doing speakers since 1973. I've got my speaker packed and ready to ship, after I give him a call tomorrow.

Post Reply