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Replacing a missing speaker - Printable Version

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Replacing a missing speaker - Eric - 06-08-2018

Good morning all!
A friend wants to restore a Stromberg Carlson Model 60
http://www.nostalgiaair.org/pagesbymodel/588/M0021588.pdf
But it is missing the speaker, there are plenty on "Play Things of the Past" that might work but nowhere is there information on the resistance of the Field coil (L-22). I'm guessing some where between 900-1100 ohms might work but it is just a guess. The schematic has no values is there a way of determining the correct resistance?

Eric

RE: Replacing a missing speaker - KCMike - 06-08-2018

Eric I found this yesterday while looking around. It is info on how to determine the approx. field coil resistance. I was going to do this when I put the Stromberg speaker in mine.
https://www.radioremembered.org/edspeaker.htm
Hope this helps you. Or maybe someone will comment further.

RE: Replacing a missing speaker - Eric - 06-08-2018

I was able to use the data in the example for all but  the 37 & 6B7 I came up with a 50 volt drop between the 80 and 41 so I had 50v/.115a ( The 41 was 37.5 x 2 = 115?) do you add up the two of them? 
I get 435 ohms ( don't think is right) 
Or if you only use one 41 tube you get 650 ohms? Does this make sense?

Eric

RE: Replacing a missing speaker - Radioroslyn - 06-08-2018

Hi Eric,
A couple points abt your FC. The only current that is passing thru it feeds mixer,if amp and 1st audio. The lion share of the current is picked off before the FC at the choke in the power supply. It power the audio output stage @ 68ma + 30ma for the other circuits
The voltage drop or resistance isn't particularly critical however the more inductance the better in will filter out the 60cy hum. I calculate abt 30ma thru the FC. Grab a filter choke measure the resistance then add a series resistor get the total resistance of 1K or so.

GL

RE: Replacing a missing speaker - KCMike - 06-08-2018

Here is a good tube data chart you can use to find all the tubes.
http://www.nj7p.org/Tubes/SQL/Tube.php
I haven't pulled the chassis yet on mine so I don't know the voltage drop across the field coil.
But just to guesstimate> lets say the total mA is 64.1 using just one 41 tube, and voltage drop is 100v that comes out to:
1562 ohms.
How did you determine your volt drop across the field coil?
I see Terry called out while I was typing. I always listen to him.

RE: Replacing a missing speaker - Radioroslyn - 06-08-2018

To be clear RCA sez a single 41/6K6 hauls down 34 ma @250v B+ so two = 68ma. But there not in the equation as the 41's are powered before the fc comes in to play.

RE: Replacing a missing speaker - Arran - 06-09-2018

Here is some much better service info then what you might find on Nostalgia Air or Riders for the S.C model 60, I think that these were scanned from factory service folders:

http://www.rsp-italy.it/Electronics/Radio%20Schematics/Stromberg%20Carlson/_contents/Stromberg%20Carlson%2060%20service%20manual.pdf

Regards
Arran

RE: Replacing a missing speaker - Chas - 06-09-2018

The Riders data includes the voltages at the speaker socket, thus all loads are accounted for. An output transformer will be required too.

Chas

RE: Replacing a missing speaker - Eric - 06-10-2018

Are you talking about using a PM speaker?

RE: Replacing a missing speaker - Eric - 06-10-2018

Mike I used the socket voltages 298v off the 80 and 250 at the 41 so a 50 volt drop?

RE: Replacing a missing speaker - Arran - 06-11-2018

Quote: "The Riders data includes the voltages at the speaker socket, thus all loads are accounted for. An output transformer will be required too.

Chas"

 See page two in the factory service folder I posted a link to, it also has a view of the socket pins above the voltage chart.
Regards
Arran

RE: Replacing a missing speaker - Eric - 06-17-2018

Replaced the all the electrolytic's and the safety caps and most of the other caps except those in the potted can. tested the tubes, the power transformer test good (worried about that one)!
Found a speaker to use as a test but am unsure of the hook up.
The output Xformer would go across # 1&6 large pins ?
and the FC would go across # 3 & 5?
Looking from the connection side of the socket going cw with the first large pin being # 1.
Do I have it right?

RE: Replacing a missing speaker - KCMike - 06-17-2018

https://i.imgur.com/GhBH1eF.jpg
Sorry I didn't get back sooner Eric. Father's day weekend had me busy.
Hope this helps let me know.

RE: Replacing a missing speaker - Eric - 06-17-2018

Mike
Happy Fathers Day to you!
And a BIG Thank You for that a lot of pieces  have fallen into place! Will try it in the morning. 
Just to be clear in my mind as you stated in the diagram chassis upside down viewing from the inside. 
Thanks again
Eric

RE: Replacing a missing speaker - KCMike - 06-17-2018

I drew that looking at the socket from the outside with the chassis turned over.