Gift: ERLA Model S-11 #16149

[vortalexfan]

Those capacitors that are in your radio that are marked "Mica Condensor" can and should be left alone as those are for the tuner and if anything having to do with the tuner is monkeyed around with, then you'll have to screw around with realigning the whole tuner circuitry to match the new parts.
Plus mica based capacitors rarely fail so they will most likely never need to be changed.

[Electronic M]

Originally Posted by vortalexfan

Those capacitors that are in your radio that are marked "Mica Condensor" can and should be left alone as those are for the tuner and if anything having to do with the tuner is monkeyed around with, then you'll have to screw around with realigning the whole tuner circuitry to match the new parts.
Plus mica based capacitors rarely fail so they will most likely never need to be changed.

I agree that micas should be considered good till proven bad, however...

Multi-tuning knob TRF sets don't really have alignment. You can tweak how close to the same knob setting each knob gets when you tune a station for peak volume, but that setup isn't at all critical to operation. Normal tuning procedure on a 3-dial TRF is not all that different from aligning a 1 dial 3-stage TRF with a 3-gang tuning capacitor...only every time you tune to a station on a 3 dial you always have to adjust the 3 tuning knobs for peak audio.

Honestly, anything short of a TV or FM radio is fairly easy to align (and even FM you can do a half-decent job of aligning by ear if you know what you are doing).

[Fran604g]

Thanks guys, I won't be swapping any components, I think this radio will have more value remaining as original - at least to me, anyway.

Here are the capacitances as they're labeled, and measured with my inexpensive LCR meter (respectively):

.005mF (5000pF) = .006mF (6000pF) - 20%
.0025mF (250pF) = .00219mF (2190pF) -10%
.00025mF (250pF) = .00029mF (289pF) - 16%

The resistances as labeled and measured (respectively):

2M = 2.5M - 25%
5R = 8.7R - 75%
10R = 10.8R - 8%

The 2 pots are both 25 ohm, not the published 30 ohm/50 ohm shown on the schematic.

I haven't checked the xformers yet. I'll probably do that sometime today.

As I mentioned earlier, there is a missing connection on one leg of one of the rheostats - the one labeled on the schem. as "50 Ohm". It's only wired to pin one (F+) of the detector tube.

I don't want to assume anything, but shouldn't the other side of this rheostat go directly to ground? Or is it supposed to be connected to one side of the C battery? I now realize the 2 pots are used for regulating the filaments. Is that how relative volume is controlled? Or signal strength? Or both?

My friend sent me a couple of newspaper ads for the ERLA that he came across while he was researching something else.

Wow, $130 in 1926! That wasn't cheap, especially considering the rapidly falling prices of a (quickly becoming obsolete) top of the line Victrola or Edison Phonograph.

[Fran604g]

Originally Posted by Electronic M

Most schematics asside from some 1920s ones have absolutely no correspondence between position of part on the page and mechanical location of part on the chassis.... honestly if you understand circuit theory it is best that the schematic not include mechanical layout to make the power and signal flow easier to read and follow.

The best thing to do is to if you are having trouble matching things on the schematic to the chassis is label each part with the letter-number designator on the schematic (some 20s schematics may need you to add your own designators). Some parts are easy to identify, and if you trace unknown parts to known then look at everything hooked to the known on the schematic you can trace it out.


TV collectors like me have to do this activity accurately on 20-40 tube TV sets regularly.

Yep. That's exactly how I do it, too. It's funny to me that the schems I've examined with similar topographies, centered the circuitry around the Detector.

My goal with this specific schematic, is to check and amend it as compared to my specific radio. The schematic I posted is of unknown origination, and there may very well have been changes by the manufacturer - as this was a very common occurrence in this time period. Technology and markets changed constantly, and manufacturers had to try and quickly respond to public demands, right?

[Fran604g]

Well, I guess that's that. I'm not getting any continuity or resistance measurements across either transformer, primary or secondary.

I'd think at least one of the four windings would show something.

[Electronic M]

Originally Posted by Fran604g

Well, I guess that's that. I'm not getting any continuity or resistance measurements across either transformer, primary or secondary.

I'd think at least one of the four windings would show something.

Audio transformers? Try putting A and B voltages to the radio. On 20s sets sometimes the open will weld closed under normal opperating conditions . On a Atwater Kent 40 I fixed for a friend both both windings of the interstage transformer tested open. We were ready to swap in a RC coupling circuit to replace it but we decided to power up the set and test with a signal source first and not only did it work but continuity returned in subsequent tests.

Same thing happened to me recently with a horn speaker that had an open voice coil...tested wide open, but I connected it to my radiola and it worked and tested as having good continuity afterwards.

Even if dead you can still replace with RC circuits with some datasheet searching and maths.

[Fran604g]

I think I finished the schematic.

I found a couple missing connections, but everything else is intact. The odd thing is the B+ 45V(Maroon) and 90V (Red) color coded wires are apparently attached reversed, in reference to a case label I found with a couple other ERLA S-11 radios. Mine is missing.

Also, I'm confused. Are those transformers, or inductors? I'm getting inductance with my LCR meter, but I'm not getting any resistance with my Fluke 89.

Forgive me for uploading small images, it's been so long since I've used this older message board format, that I've forgotten how to load them in the text window.

[bgadow]

Regarding the open end of the rheostat, that should be to A+, normally. On the AK 20 I have on the bench one end of the wire had detached. There was enough in the winding that I could carefully pull out 1/4" and solder that to the lead.

One of the rheostats controls the filament for detectors and the other for amplification. Depending on signal strength you may have to adjust one or both for best results. If one of them is open then some tubes won't light at all. If you needed to temporarily you could run a jumper and run all filaments off of the one good rheostat. For that matter, you could just run 6v direct to the filaments, for testing purposes.

[Fran604g]

Originally Posted by Electronic M

Audio transformers? Try putting A and B voltages to the radio. On 20s sets sometimes the open will weld closed under normal opperating conditions . On a Atwater Kent 40 I fixed for a friend both both windings of the interstage transformer tested open. We were ready to swap in a RC coupling circuit to replace it but we decided to power up the set and test with a signal source first and not only did it work but continuity returned in subsequent tests.

Same thing happened to me recently with a horn speaker that had an open voice coil...tested wide open, but I connected it to my radiola and it worked and tested as having good continuity afterwards.

Even if dead you can still replace with RC circuits with some datasheet searching and maths.

Thank you, I'll try that once I put together a suitable A/B/C PS.

[Fran604g]

Originally Posted by bgadow

Regarding the open end of the rheostat, that should be to A+, normally. On the AK 20 I have on the bench one end of the wire had detached. There was enough in the winding that I could carefully pull out 1/4" and solder that to the lead.

One of the rheostats controls the filament for detectors and the other for amplification. Depending on signal strength you may have to adjust one or both for best results. If one of them is open then some tubes won't light at all. If you needed to temporarily you could run a jumper and run all filaments off of the one good rheostat. For that matter, you could just run 6v direct to the filaments, for testing purposes.

Thanks Bryan, I amended my schematic to reflect your information. I had a feeling that the rheostats were used for that purpose, but it's good to have confirmation.

There was another suspect connection shown in the "original" schematic I posted earlier, but it doesn't exist in my radio. It is shown coming off V3 pin 1 (F+) in parallel with V5 pin 1 (F+) going to the 25 Ohm pot. Would there have been a connection there, and if so, for what purpose do you think?
ERLA S-11 SN-16149 SCHEMATIC AMENDED 8-14-2019 FWP.jpg

As for a signal in, and a loudspeaker or phones, what should I use for a quick and dirty (reliable?) antenna, and what impedance loudspeaker can I get away with? I have a pair of old (1960's) Lafayette headphones that still work, and plenty of speakers laying around. Would an 8 ohm full range speaker be okay? I don't want to kill a good speaker screwing around - if I can help it.

[Electronic M]

These sets expected 500 ohm headphones / speaker or higher impedance. If you don't have proper 20s era phone's get the audio output transformer from a tube radio and use that to match the impedance.

[Fran604g]

Originally Posted by Electronic M

These sets expected 500 ohm headphones / speaker or higher impedance. If you don't have proper 20s era phone's get the audio output transformer from a tube radio and use that to match the impedance.

Thanks Tom.

An addendum to an earlier post I made:

I uncovered a section of the wiring harness viewed under different lighting, and discovered that the wire I initially thought was Red (B+90V) is actually the Maroon (B+45V).

THAT makes more sense. The schematic has been edited to reflect this discovery. I'm still curious as to why there would've been shown an unknown connection off of V31, and V51?

[Fran604g]

Why the hell would a link be placed onto the words "wiring harness" in my last post? I didn't do that!

[Electronic M]

Originally Posted by Fran604g

Why the hell would a link be placed onto the words "wiring harness" in my last post? I didn't do that!

Skimlinks add reasources....it is a way for VK to make money. You'll see people intentionally miss spell stuff to avoid skimlinks grabbing it and making it a link...I haven't seen skimlinks in any VK post in years by using Firefox with an ad blocker add on... enough of the ads on the net are exceptionally obnoxious and or full of viruses that I try to eliminate almost all of them.

[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