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

radio, tape, stands and accessories
Coffee Phil
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Re: I'm in the really OLD radio and SET clubs now.

Post by Coffee Phil » 17 Apr 2016 23:11

The speaker for my Radiola 18 radio arrived a couple of days ago. It is a Radiola 100A.

Here is the front view:

[album]35170[/album]


Rear view:

[img]35171[/img]

This looks pretty much like the front except for the cord. The driver is mounted to the front.

This is the interior view from the bottom with the cover removed:

[img]35172[/img]

Note that this is unlike the moving coil speakers which we know and love today. It is a balanced armature type. The cylindrical device is some sort of filter. I'm guessing series inductor and shunt capacitor. This speaker has a DC resistance of over 1 k Ohm and is driven from the 71A output tube in the radio via a coupling capacitor. No audio output transformer.

This is the bottom cover showing the label:

[img]35173[/img]

For what I paid for it this speaker appears to be in pretty good shape. The case is metal and should be paintable with a rattle can. I need to figure out how to restore the gold trim around the grills. The front grill cloth looks good enough to wash with cold water and reuse. I may need a small iron-on patch on the rear. I have not had a good look at the cone but the coil has continuity and clicks emanate from the speaker when I test the coil with an ohmmeter. So far I have not applied audio to it. Hopefully I'll try that tonight. If it sounds reasonable I just look for the correct connectors for the the cable and move on to sorting out the radio. What reasonable sound from this thing is is something I'm not sure of as I don't think I have ever heard a moving iron speaker before, other than the clicks from this one.

Phil

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

Post by analogaudio » 18 Apr 2016 00:42

I notice the RCA label has a lot of fine print, what does the notice say?

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

Post by spittenkittens » 18 Apr 2016 00:56

A real beauty! will look even better just cleaned up. Good luck with the project. I would like to see it when done.

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

Post by Coffee Phil » 18 Apr 2016 03:10

Hi Ted,

Here it is:

Notice

In connection with devices it sells, Radio Corporation Of America has rights under patents having claims (A) on the devices themselves and (B) on combinations of the devices with other devices or elements as for example in various circuits and hookups. The sale of this device carries a license under the patent claims of (A) but only for (1) talking machine uses, (2 ) radio amature uses, (3) radio experimental uses and (4) radio broadcast reception, and only where no business features are involved.
This sale does not carry a license under patent claims of (B) except only (1) for legitimate renewals and repairs in apparatus and systems already licensed for use under such patent claims on combinations (2) for assembling by amateurs and experimenters and not by others with other licensed parts or devices or with parts or devices made by themselves but only for their own amature and experimental radio uses where no business features are involved and not for sale to or for use by others. (3) For use with licensed talking machines and licensed radio broadcast receiving devices and only where no business features are involved.
Patents 1271527 1271529 13658988 1631646

Now I'm not an attorney but What I get out the above is that while Sarnoff may not been keen on paying for the patents on the neutralized triode RF amplifier, you best not mess with his intellectual property.

Phil

analogaudio wrote:I notice the RCA label has a lot of fine print, what does the notice say?
Last edited by Coffee Phil on 18 Apr 2016 06:49, edited 1 time in total.

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

Post by Coffee Phil » 18 Apr 2016 03:19

Hi Spittenkittens,

Thanks. I think it will clean up without too much effort. I hope to feed some audio into it tonight. If it works, I'll turn my efforts to the radio to see what I have. After they are working together I'll try to make them presentable.

Phil

spittenkittens wrote:A real beauty! will look even better just cleaned up. Good luck with the project. I would like to see it when done.

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

Post by Coffee Phil » 18 Apr 2016 06:46

The old speaker Lives! I took the WW2 phone plug off and attempted to tin the leads. So far no joy with that. It appears to be the OEM cable with braided copper conductors. I want to keep the cable so I'll need to figure a way to tin the leads to accept the proper pins. Rosin flux is not touching it. I got it good enough to measure continuity so I connected it to a little sand amp I built many years ago. I plugged my i-phone into the amp and out came James P. Johnson from the ancient speaker, then some Ella, then some Fats Waller, then the Jim Cullum band playing Eventide (Abide With Me). While I wouldn't trade my ESS tempests for a pair of these, for an ancient loudspeaker technology which we haven't used since ~1930 it sounds pretty good. I'd be willing to bet that this is the first time the old speaker was driven by sand. I think this it the first time I have ever heard a balanced armature speaker. I'm a happy old radio guy.

Now to see what it does with the SET in the old Radiola 18 TRF.

Phil

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

Post by spittenkittens » 18 Apr 2016 14:45

Cool, the speaker grill looks to be in fair shape too.

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

Post by analogaudio » 18 Apr 2016 17:16

Thanks Phil. Amazing what a piece of vibrating paper can do :-)

If that's what they put on the back of a loudspeaker imagine what they would want to put on the back of a smartphone :-)

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

Post by Coffee Phil » 18 Apr 2016 18:12

Hi Ted,

Be careful! Don't give them any such ideas. We may end up having to read and accept a bunch of crap like that before making a call!

Phil
analogaudio wrote:Thanks Phil. Amazing what a piece of vibrating paper can do :-)

If that's what they put on the back of a loudspeaker imagine what they would want to put on the back of a smartphone :-)

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

Post by Coffee Phil » 18 Apr 2016 18:47

Hi Tony,

The development of radio over that decade was amazing. This radio used a balanced armature loudspeaker which I believe was reaching the end of its life by then. In 1937 virtually all radios had moving coil speaker not too unlike what we have today.

This radio has very primitive gain management with the volume potentiometer in front of the first RF amplifier and wide open gain the rest of the way to the speaker. In 1937 virtually all radios would have automatic volume control with the audio level out of the detector feedback controlled and the volume control in the audio stages.

I believe that Armstrong invented the superheterodyne in 1919 but in 1927 all but the very high end radios were still TRFs. By 1937 virtually all radios were superhets.

Most 1937 broadcast radios would at least equal what came since. OK, my Carver TX 11a has selectable IF bandwidths and even AM stereo but it is hardly mainstream.

Phil

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

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

Post by Big B5515 » 19 Apr 2016 07:54

Coffee Phil wrote:The old speaker Lives! I took the WW2 phone plug off and attempted to tin the leads. So far no joy with that. It appears to be the OEM cable with braided copper conductors. I want to keep the cable so I'll need to figure a way to tin the leads to accept the proper pins. Rosin flux is not touching it. I got it good enough to measure continuity so I connected it to a little sand amp I built many years ago. I plugged my i-phone into the amp and out came James P. Johnson from the ancient speaker, then some Ella, then some Fats Waller, then the Jim Cullum band playing Eventide (Abide With Me). While I wouldn't trade my ESS tempests for a pair of these, for an ancient loudspeaker technology which we haven't used since ~1930 it sounds pretty good. I'd be willing to bet that this is the first time the old speaker was driven by sand. I think this it the first time I have ever heard a balanced armature speaker. I'm a happy old radio guy.

Now to see what it does with the SET in the old Radiola 18 TRF.

Phil
One thing that may help with tinning the braided wire is to burn away (with a flame) the string woven in with it at end, then carefully clean remaining copper with 400 - 600 grit sandpaper. Nice to hear you have a working speaker, I'm expecting my speaker rebuild to be done sometime next week. On my 1931 radio, every cap (except micas) checked bad, and one tube had intermittent shorts, the combination of which had burned up the field coil and volume control.

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

Post by Big B5515 » 17 Oct 2016 21:44

After attending my first radio auction, I believe I may have also joined those really old radio and triode clubs with this doozy, a ~1929 Victor R32, and all for the pricy sum of $10. It is in fairly good cosmetic condition, apparently missing only a 1\2 dial scale, and 2 #45 output tubes. I confirmed field coil voice coil, and output transformer were not open and had plausible resistance, confirmed remaining tubes test good (6 #26, 1 #27, and a #80), then smoke tested power transformer for four hours without rectifier, all seemed good, and tubes light. I want to do some research before going farther, but now feel it should be worth a reproduction dial scale, and good used pair of 45s anyway. I will mention that it is very heavy, and will probably remain in dining room against wall behind where picture was taken, and a much more solid stand for the Dual 1019 turntable under napkin.

36500
36507

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

Post by Coffee Phil » 18 Oct 2016 00:37

Hi Big B,

I think you did well here. That is a nice looking radio. I'm guessing it is just a bit newer than my Radiola 18 and much higher end. I'm guessing newer since it has a moving coil speaker, but not too much newer as it is appears to be a TRF with triode RF stages. Sarnoff did not like paying royalties for the neutralized triode RF amp so they developed the 24a tetrode in about that time frame.

I think this is one you should get working. It should not be too bad as these are fairly simple radios. You should be able to start trouble shooting before you find the 45s by monitoring the signal to the grids of the output tubes with your oscilloscope.

RF alignment should not be too bad, but you may have the added step of neutralizing each RF stage. You disable each stage by either disconnecting one of the filament leads to each 26 and adjusting the neutralizing trimmer in that stag for minimum signal transfer. Radio techs in the day kept 26 tubes with a filament pin cut off for the purpose. I have two 26 tubes with open filaments (bummer as they are the old style) which may work if you don't want to bother with disconnecting and connecting the filaments. Since I have two, I'll give you one if you want it. We sure don't want to be chopping filament pins off of functioning 26 tubes today.

Good luck with this and please keep us posted with pictures.

I like some of the other radios which you picked up. In particular the Zenith console. When I was a kid figured that someday I would own one of those Hallicrafters communications receivers. So far it hasn't happened.

Phil

Big B5515 wrote:After attending my first radio auction, I believe I may have also joined those really old radio and triode clubs with this doozy, a ~1929 Victor R32, and all for the pricy sum of $10. It is in fairly good cosmetic condition, apparently missing only a 1\2 dial scale, and 2 #45 output tubes. I confirmed field coil voice coil, and output transformer were not open and had plausible resistance, confirmed remaining tubes test good (6 #26, 1 #27, and a #80), then smoke tested power transformer for four hours without rectifier, all seemed good, and tubes light. I want to do some research before going farther, but now feel it should be worth a reproduction dial scale, and good used pair of 45s anyway. I will mention that it is very heavy, and will probably remain in dining room against wall behind where picture was taken, and a much more solid stand for the Dual 1019 turntable under napkin.

36500
36507

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

Post by Big B5515 » 18 Oct 2016 01:33

I definitely think I'll take my time with this one, and the Zenith. Both cabinets only need minor touch ups and repairs. I don't know what to expect in this victor, but figured I better get into it and check resistors and capacitors, ect, before powering it up with rectifier installed. I measured 435VAC-ct (870V) on secondary of this beast, with a very large 3000ohm field coil.

I've yet to power up the Zenith, but did check tubes, the majority oem and still strong. I read suggestions of replacing the 6x5s with silicon diodes on these to prevent transformer damage. The Truetone, unfortunately came with a few weak \ bad tubes, rusty chassis, overextended band switch, open output transformer, and a mess underneath associated with new wiring to glued in dead eye tube. All this was cleverly hidden behind a homemade pegboard rear cover from years ago. It could be a bit of a project to restore.

I tried the hallicrafters last night, has several orange dip caps already and works well on first 3 bands (up to 14mhz). I could tune in my signal generator on upper band, but not much else. It has the good style IF transformers, but didn't come cheap ($37), and appears someone repainted parts of it with a brush. I still think it will make a nice short wave receiver with ssb capability, and appears to use an octal AA5 tube set.

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

Post by Big B5515 » 22 Oct 2016 09:41

A pair of cheap ($49 delivered) used Sylvania #45 tubes arrived for the Victor, One with newer style printed base and testing a lot better on life test, but otherwise both showing equally good at full voltage. After a bit of research, I got brave, and decided to power it up with a 200W bulb in series and variable transformer, the radio does seem to work ok. Unfortunately, the Phono input doesn't work, likely an open transformer winding, and it also possibly has a bad spot in the double volume control. Still, it played very loudly in center of dial with a ~20 ft wire antenna, but seemed to be lacking reception at top and bottom of dial, maybe the neutralizing adjustment? It sounds distorted with a weak signal \ reduced volume level, but surprised me with it's clarity and loudness on strong signal.

I also figured out that the Zenith is a 10A1 chassis and appears to be a later design with a separate heater winding tied to B+ for the 6X5GTs, each rectifier tube connected to only 1 tap of secondary. I successfully repaired the broken wires on it's external antenna coil, but an attempt to slowly power it up as found only gave a loud hum.