Northern Electric Co.

[Gerry O’Hara]

Aha! – that’s why Midwest put so many tubes in their sets. An answer, finally….

Some great info and links in some recent posts on the Forum – very interesting. Thanks for the contributions folks!

Gerry (CVRS Newsletter Editor/Forum Moderator)

[Eric Strasen]

Gerry,
This link to the Antique Radios site provides the ultimate Midwest Radio Co. tube count overkill…
https://www.antiqueradios.com/forums/viewtopic.php?t=129999.
This should warm up an entire province, if it’s still around and you could get your hands on it.
Eric S.

• This reply was modified 3 years, 2 months ago by Eric Strasen.

[Eric Strasen]

Jean,
Earlier in this thread you asked me to comment on the Zener diode replacement for the cathode resistor in AA5 and AA6 sets.
Early this a.m., I was rummaging about in the shop looking for some knob felts. I didn’t find them, but I did locate my treasure trove of Zeners. The mailman just now dropped off another shipment of them. I now have enough diodes to last a lot longer than I will.
I really got to get organized…
I installed one in the Baby Champ. It works just fine, but frankly I can’t tell the difference in audio quality.
I have so many of the darn things that I will be putting them in every AC/DC set I open up, however.
I also tried the Northern Electric with a 10 watt, 82 ohm resistor in the filament string, figuring it might run cooler than the two watt carbon job the factory put in the radio.
It didn’t.
The set is now running with a 50L6 and no resistor, as you originally recommended.
It takes me a while to learn, and that’s not advanced age. Been that way all my life.
I do have a nice six tube Bendix on the bench. It has a 4X6″ speaker and a Zener diode might make an audible difference there.
Eric S.

[Jean Marcotte]

Eric,
Thanks for report. It is not surprising that the difference, if any, is not audible on such a set. If you look at the power consumption (plate current plus grid no.2 current) of a 35L6 at zero signal (43 ma) and maximum signal (48 ma) the voltage change at the cathode is probably negligeable and of course we never listen to these sets at maximum signal. But I retain the idea for future use in some better sets.

For the 82 ohms resistor, it has to drop 1et’s say 12V at .15A wich amounts to 1.8 watt. A two watts resistor is really a minimum. Putting a higher watt value resistor will ensure that the resistor won’t go up in smoke but it will still dissipate 1.8 watt of heat. Now if you put a “really” big resistor that heat will be dissipated on a larger surface and it might feel cooler but the total heat generated will still be 1.8 watt.

Jean

[Eric Strasen]

Jean,
Upon further listening, The Baby Champ does, indeed, sound better at very high volume levels with the Zener diode; however, for whatever reason the audio is quite distorted at LOW levels.
A lot of imponderables here. Does the bypass cap have something to do with this? Do I need to use a volume control of a differing impedance?
This time I’ll probably do the simple thing and just put a resistor back on the cathode and chuck the diode.
Now, I just need to find a project that uses 100+ Zeners…
As far as the 82 ohm voltage dropping resistor goes: the new 10 watt wirewound is virtually the same physical size as the old 2 watt carbon, so the amount of heat dissipated does feel the same to the touch.
Eric

[Eric Strasen]

Jean,
After consulting via Email with my Georgia electronics engineer friend, I find I misspoke in an earlier reply to your question about the cathode bypass capacitor on the Baby Champ (and other AA5 or AA6 radios). It should be removed as it serves no purpose, except to possibly introduce distortion, once a Zener diode as been substituted for the cathode resistor.
If low-level audio distortion persists when the cathode cap is removed, he suggests I check the value of the plate resistor on the first audio 12SQ7 to make sure it is within tolerance and replace the coupling capacitor from the center of the volume control to the 12SQ7 grid.
I haven’t done any of these things yet as I have other projects going, including customizing some nice old Triplett 3413 emissions tube testers.
Eric S.

• This reply was modified 3 years, 2 months ago by Eric Strasen.

[Eric Strasen]

Due to the continuing frigid below zero (F) weather hereabouts, I have been firmly anchored in my living room recliner chair, laptop in lap, aimlessly surfing the net.
I once again Googled Northern Electric “Baby Champ” and this schematic popped up.
All is clear now.
Merry Christmas and a happy New Year to all,
Eric S.

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   circuit_diagram.png
   

[Jean Marcotte]

Gee! I thought you would never find the answer. Watch for that strange tube at the top with the two arrows. It’s always the one to fail first.

Merry Christmas to all of you guys.

Jean

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