Gift: ERLA Model S-11 #16149

[Fran604g]

Originally Posted by jr_tech

The lower end of the variable resistor from pin 1 of V1 should connect to ground. And yes, I would replace the missing wire from the antenna coil to ground.

jr

Okay, I'll put those connections back into my schematic. Any idea what the external connection shown at V3 1 represented? There is a GRD post topside that isn't shown in the schematic I'm using to redraw. I wonder if this connection was an error by whomever drew the "original".

[jr_tech]

Perhaps a test point, for setting/monitoring the voltage applied to the filaments of the RF amplifier tubes.

jr

[Fran604g]

4 out of the 5 UX201A's test very strong, so that's a "plus". I won't be spending any more time on this for now. I'm pretty happy with how well she cleaned up - not a beauty queen by any stretch, but at least I was able to save and preserve her for future generations.

Maybe someday I'll come back to her, build a battery eliminator or appropriate battery box, replace the 2 bad interstage xformers, string up an antenna, and fire her up to dial in that singular 550kHz station...

A sincere "Thank you" to everyone who helped me out. As time progresses, I'll keep her in my thoughts, and add historical information to the file on the ca.1925 ERLA S-11 TRF 5-tube radio I now have alongside my talking machine collection.

Cheers,
Fran

[teevee]

Usually, the RF stages were in the 1,3,5 tube positions, (separation to avoid feedback), and the audio amps in the 2,4 position. Easy enough to figure out, you can start at the antenna or speaker term and trace them out..
1. all the filaments lit? If so, check the plate voltages. Usually, the audio transformers primary windings are open (corrosion) so no plate voltage. Secondaries are not immune..

[Fran604g]

Originally Posted by teevee

Usually, the RF stages were in the 1,3,5 tube positions, (separation to avoid feedback), and the audio amps in the 2,4 position. Easy enough to figure out, you can start at the antenna or speaker term and trace them out..

That's exactly what I discovered while I traced out the schematic on my own. Initially I had some difficulty trying to understand the relationship between that hand-drawn schematic I posted back on pg.1, and what was going on with the actually physical layout of the circuitry.

I did eventually identify a few inaccuracies between that suspect schematic, and my radio. Other Model S-11's could be different I suppose (that was very typical for the antique talking machine industry of the same period - and throughout its entire earlier history), but I've reconciled most of my difficulties in understanding what's going on. Thanks for your input.

Originally Posted by teevee

1. all the filaments lit? If so, check the plate voltages. Usually, the audio transformers primary windings are open (corrosion) so no plate voltage. Secondaries are not immune..

I determined both xformers are open on all 4 windings, sadly, and I won't pursue powering the radio up anytime soon. I'm happy with it being a shelf queen for now. If/when I ever do proceed beyond this point, I'll probably build a battery eliminator, so that I might be able to add more even earlier TRF radios (and especially a "homebrew") to my fairly extensive acoustic phono collection.

Maybe.

With over 30 acoustic spring-wind machines in my home, ranging from 2 minute cylinder players from as early as a ca.1895 Graphophone Type N, and many Edison Phonographs; a couple 4-minute Edison Amberolas (including a very nice and HTF oak Model V); several disc machines ranging from a ca.1901 pre-dog Victor Type C; a couple Victrolas; several Diamond Disc Phonographs produced from as early as 1916 to as late as my ca.1927 Edisonic "Schubert" (and also including an Edison "Long Playing" Model 1-C Phonograph); and books. Tons of books, too. All this takes up the entire downstairs of my home, and a little of my barn.

They're my true passion.

Oh, yeah, and then there's the "Audiophile" stuff, too. Space is always at a premium, as we all know.

Best regards,
Fran

[init4fun]

Wow Man , , , , like , Frantastic ! .....

[Electronic M]

Wow nice acoustic phonographs.

You know you can replace each audio transformer with 2 resistors and a capacitor.... disconnect the old transformers and place a 10K ohm resistor in circuit between the points the plate winding of the audio transformer once connected, take a 1-2M ohm resistor and connect it across the points the grid winding once connected, now connect the plate lead to the grid of the next tube with a .1uF capacitor, rinse and repeat for the other bad audio transformer.....I can draw you a schematic later if you would like.

[teevee]

Have you looked inside the xfmrs? If the core size is 1/2", you may still be able to get a bobbin (windings) from antique electronic in Tempe. I've "rebuilt" a few transformers over the years doing this. It's difficult, and messy, but.... For other sizes I've had to resort to other methods. I did one where I replaced the iron with a piece of pine, (hollowed out to take the modern transformer) and then wire brushed the wood to "line" it so it looked 9under the flat black paint) like laminations.

http://www.oldradiosrus.com/build.html

There are 2 xfmr rebuilds shown on that page...

[teevee]

Hammond 124A xfmr or 124C (coil only)

[Fran604g]

Originally Posted by init4fun

Wow Man , , , , like , Frantastic ! .....

Originally Posted by Electronic M

Wow nice acoustic phonographs.

You know you can replace each audio transformer with 2 resistors and a capacitor.... disconnect the old transformers and place a 10K ohm resistor in circuit between the points the plate winding of the audio transformer once connected, take a 1-2M ohm resistor and connect it across the points the grid winding once connected, now connect the plate lead to the grid of the next tube with a .1uF capacitor, rinse and repeat for the other bad audio transformer.....I can draw you a schematic later if you would like.

Thanks, I didn't know that. That's a simple solution, for sure - "capacitor coupling" the stages instead of a transformer? Is that the correct terminology for the circuit?

Like this?

[Fran604g]

Originally Posted by teevee

Have you looked inside the xfmrs? If the core size is 1/2", you may still be able to get a bobbin (windings) from antique electronic in Tempe. I've "rebuilt" a few transformers over the years doing this. It's difficult, and messy, but.... For other sizes I've had to resort to other methods. I did one where I replaced the iron with a piece of pine, (hollowed out to take the modern transformer) and then wire brushed the wood to "line" it so it looked 9under the flat black paint) like laminations.

http://www.oldradiosrus.com/build.html

There are 2 xfmr rebuilds shown on that page...

Originally Posted by teevee

Hammond 124A xfmr or 124C (coil only)

Thanks Tom! I'm not sure I'll try restuffing the tranny's, but you never know.

[Electronic M]

Originally Posted by Fran604g

Thanks, I didn't know that. That's a simple solution, for sure - "capacitor coupling" the stages instead of a transformer? Is that the correct terminology for the circuit?

Like this?

Yes but the grid resistors need to be 1-2 Megaohms not kiloohms. Once it is passing audio you may want to experiment with caps between .47 and .01, plate resistors between 8k and 15k, etc to optimize volume and tone. Audio amplifiers of that time were spectacularly inexact devices and could opperate deceptively normally with component values far from design or optimum.
What I gave you should get it to pass audio.
You will need a high impedance speaker/headphones or an audio matching transformer and a low impedance speaker... the plate resistance of a 01A is 11k ohms so you want an audio transformer with a primary impedance between 9k and 13k, and a secondary impedance that matches your speaker. Any transformer rated over 5W is probably over kill.

[Fran604g]

Thanks Tom, my mistake! I'm happy you caught that typo.

Fran

[Fran604g]

Originally Posted by Electronic M

Yes but the grid resistors need to be 1-2 Megaohms not kiloohms. Once it is passing audio you may want to experiment with caps between .47 and .01, plate resistors between 8k and 15k, etc to optimize volume and tone. Audio amplifiers of that time were spectacularly inexact devices and could opperate deceptively normally with component values far from design or optimum.
What I gave you should get it to pass audio.

For posterity, here's the amended (final?) schematic with coupling caps and resistors bypassing the the two transformers:

Originally Posted by Electronic M

You will need a high impedance speaker/headphones or an audio matching transformer and a low impedance speaker... the plate resistance of a 01A is 11k ohms so you want an audio transformer with a primary impedance between 9k and 13k, and a secondary impedance that matches your speaker. Any transformer rated over 5W is probably over kill.

I think I'm slowly becoming convinced that I should try this. I'll have to dig around my various parts stashes and see what I may have. I know I have some 70V PA speaker transformers that came with some full range 8" Jensens- would they do the job, do you think, or would the primary impedance be too low? I don't know how to determine those impedances between the windings.

I have some other old 40's-50's radios out in the barn, I can see if I can determine the values of their output trannys.

Sorry for all the probably stupid questions.

[init4fun]

Hi Fran , Tom's method will work for you , I've done this many times and in fact I did the very same thing recently to a Temple brand TRF radio and it worked great . A couple of fine tuning tweaks here may be to use smaller capacitors for the coupling , I've usually found that much over .001 caused distortion , and with the Temple there was a bit of a buzz in the sound till I fed the plate resistor(the 10K resistor) with a small RF choke . The radio I did had only one bad interstage transformer and was an A/C powered unit , if you run your's from batteries you may not need the RF choke .

PS , there are no stupid questions here , we are mostly old men ( Tom being the exception) who have spent a lifetime learning this stuff , and we are here specifically to help people learn what we spent all those years learning . Oh , and I love the "I is for him , E is for her" , my middle name is Francis and many people don't know the I or E spelling for male or female