Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Dec Mon 17, 2018 8:57 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 1268 posts ]  Go to page Previous  1 ... 59, 60, 61, 62, 63, 64  Next
Author Message
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Wed 19, 2018 3:43 am 
Member

Joined: Aug Wed 04, 2010 5:40 pm
Posts: 327
Location: Tyngsborough, Massachusetts
Michael, Thanks for the information and links.

The extra knob controls the filament voltage to the oscillator tube, The upper speaker jack takes the signal from the plate of the first audio tube. If a speaker is plugged into it, it disconnects the signal to the second audio tube. The lower jack is from the plate of the second audio tube and is configured such that unless a plug is in the jack, no power gets to the second audio tube filament.

Jeff


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Wed 19, 2018 3:59 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 837
Location: Utah 84065
Nice find on the Leutz C-7!
The IF transformers, though not the large bulky type, are correct for your set.
Here are a couple of photos that came from ebay several years ago:

Image

Image

And here is a photo of the transformer being used in a C-10:

Image

_________________
www.duanesradios.info


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Wed 19, 2018 1:37 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 1770
Location: Hollywood, Maryland
Duane,

Why are those IF's correct for a C-7 build? Have you seen other C-7 sets using the same IF's? Was there a change, and later C-7 radios were built with the C-10 shielded IF's?

Someone should publish an article on the C.R. Leutz family of radios and document known variations not documented in the Leutz books.

David W.


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Wed 19, 2018 5:27 pm 
Member

Joined: Nov Sun 04, 2007 6:01 am
Posts: 3014
Location: Redding, CA
Wouldn't it be a Model C being that it has eight tubes (one socket empty)? I thought the C-7 was so named because it had one less tube.

Norman

_________________
"No home is complete without music" - Capehart Sound Amplifying and Distributing Systems


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Wed 19, 2018 6:25 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 837
Location: Utah 84065
David: Michael Feldt has a C-7 with the same transformers.

http://www.indianaradios.com/C.%20E.%20 ... rodyne.htm

I suspect that this style of transformer is later than the large bulky EIS transformers.
EIS probably started making them like this when the C-10 came out.

Norman: This radio does have 7 tubes. The top of one of the IF transformers is reflecting light, and it may look like the eighth tube.

_________________
www.duanesradios.info


Last edited by Duane B on Sep Wed 19, 2018 6:53 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Wed 19, 2018 6:31 pm 
Member

Joined: Nov Sun 04, 2007 6:01 am
Posts: 3014
Location: Redding, CA
Look below the power switch near the lower right corner of the photo. The final audio tube is missing from its socket.

Norman

_________________
"No home is complete without music" - Capehart Sound Amplifying and Distributing Systems


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Wed 19, 2018 6:45 pm 
Member

Joined: Aug Wed 04, 2010 5:40 pm
Posts: 327
Location: Tyngsborough, Massachusetts
The radio does have seven tubes. As I noted, the second audio tube is not in its socket. What might look like a tube in the center is actually the top of an IF transformer can, as Duane also noted. I was wearing a headlamp when I took the photo, and the shiny transformer can reflected the light back into the camera.

Good information on the IF transformers. Thanks.

Jeff


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Wed 19, 2018 6:53 pm 
Member

Joined: Nov Sun 04, 2007 6:01 am
Posts: 3014
Location: Redding, CA
Got it. So that is not an Arcturus tube in the middle!

Norman

_________________
"No home is complete without music" - Capehart Sound Amplifying and Distributing Systems


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Fri 28, 2018 12:09 am 
Member

Joined: Aug Wed 04, 2010 5:40 pm
Posts: 327
Location: Tyngsborough, Massachusetts
I powered my Leutz C-7 up and it works quite nicely. It took several power supplies, and two bias supplies to run it. I'll probably build a combination power supply to go with it.

I've got a couple of questions, one specifically about the Leutz C-7 and the other about these early superhets in general.

The first question is the Leutz C-7 schematic shows the oscillator tube filament connected directly to the A battery supply with no dropping resistor. If a 6 volt A battery were directly connected to the A inputs, wouldn't that put excessive voltage on the filament or were these radios used with an additional external rheostat? Mine has a rheostat on that filament line, so it's not an issue.

The second question is how were these radios generally tuned to a station? I used an oscilloscope with frequency display to get the tuning set up, but what would the procedure have been in 1925 or thereabouts? I can see how multidial TRFs get tuned, but without the scope I can't see how you'd start to tune the set.

Jeff


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Fri 28, 2018 12:58 am 
Member
User avatar

Joined: Sep Thu 14, 2006 3:27 pm
Posts: 11395
Location: Carmel, Indiana
jeffs01879 wrote:
I powered my Leutz C-7 up and it works quite nicely. It took several power supplies, and two bias supplies to run it. I'll probably build a combination power supply to go with it.


I have a Leutz C-7 and all that's needed to power it up is a ARBE-II power supply. It has all of the proper voltages and current capability to run a C-7 for hours.

ARBE-III webpage: https://www.arbeiii.com/

_________________
Michael Feldt
www.indianaradios.com


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Fri 28, 2018 1:27 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 837
Location: Utah 84065
jeffs01879 wrote:
The first question is the Leutz C-7 schematic shows the oscillator tube filament connected directly to the A battery supply with no dropping resistor. If a 6 volt A battery were directly connected to the A inputs, wouldn't that put excessive voltage on the filament or were these radios used with an additional external rheostat? Mine has a rheostat on that filament line, so it's not an issue.


I've never noticed the A battery connections to the oscillator tube before. When I first saw your post I checked the C7 schematic and assumed that it must be an error on the schematic. However, I then checked my C-7 and it is indeed wired like the schematic - the oscillator tube filament is connected directly across the A battery with no rheostat control! I still don't think this is how it should be. I think the schematic has an error and people wired the set wrong by following the schematic!

Image

_________________
www.duanesradios.info


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Fri 28, 2018 1:44 am 
Member

Joined: Aug Wed 04, 2010 5:40 pm
Posts: 327
Location: Tyngsborough, Massachusetts
Duane, I would think a lot of oscillator tubes had pretty short lives if they were connected directly to the A battery. I had wondered if they needed the higher voltage to get the circuit to oscillate reliably, and shorter life was the price that was paid. But I had no trouble getting mine to oscillate consistently with between 4 1/2 and 5 volts on the oscillator filament, and in mine the tube in that socket is not as strong as it could be.

The oscillator filament rheostat on mine was obviously an addition, it has a different knob and the rheostat itself is a bit different from the other two rheostats.

Michael, thanks for the information on the power supply.

Jeff


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Fri 28, 2018 1:56 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 837
Location: Utah 84065
You've got a great set Jeff. I really like it!

Referring to the schematic above, I'm thinking the oscillator tube and the 2nd RF tube should probably both be controlled by the 20-ohm rheostat.

_________________
www.duanesradios.info


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Fri 28, 2018 2:13 am 
Member

Joined: Mar Mon 05, 2012 6:35 am
Posts: 303
Location: Chicagoland, 60194
It's been so long I've forgotten some details, but as I recall the early C7's using early style 201 tubes put a bias voltage on the RF xfmrs which was indicated in the original schematics found in Leutz 1st edition book. The 2nd edition book has a mention in it somewhere that it was no longer needed with the new 201A tubes. 1st edition and 2nd edition books are also often misidentified because Leutz dated his first 1924 released book with a 1925 date. I think I posted this info here in the past, but wasn't able to find it.


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Fri 28, 2018 2:21 am 
Member

Joined: Aug Wed 04, 2010 5:40 pm
Posts: 327
Location: Tyngsborough, Massachusetts
Duane, I lucked out. A radio like this was not even on my radar, then it fell into my lap. Long story. I've had a lot of fun with it already and I've only had it less than two weeks. And it's in really nice condition. Condition-wise it doesn't look 95 years old.

You may be right about the oscillator filament connecting to the rheostat for the second RF tube. I wonder why the second RF tube has its own separate filament control.

The missing rheostat is not so much an issue these days because probably most folks use power supplies rather than batteries, and it's easy enough to connect just 5 volts to the A terminals and run the rheostats near maximum, but it had to be a problem back when most of these sets were powered by wet cells.

Jeff


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Fri 28, 2018 2:29 am 
Member

Joined: Mar Mon 05, 2012 6:35 am
Posts: 303
Location: Chicagoland, 60194
Found my note: Bias from audio -4.5 C supply connected to both IF transformer secondary per original schematic. This increased response, but also caused unwanted oscillations so returned as found. RF (IF) bias removal was recommended by Leutz in MRR 2nd edition (Feb1925) p174.


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Fri 28, 2018 4:09 am 
Member

Joined: Aug Wed 04, 2010 5:40 pm
Posts: 327
Location: Tyngsborough, Massachusetts
Mine is configured to provide the 4.5 volt C supply to only the two audio stages.

Jeff


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Fri 28, 2018 2:52 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 13108
Location: S. Dartmouth MA 02748-1225 USA
jeffs01879 wrote:
...The missing rheostat is not so much an issue these days because probably most folks use power supplies rather than batteries, and it's easy enough to connect just 5 volts to the A terminals and run the rheostats near maximum, but it had to be a problem back when most of these sets were powered by wet cells.
Jeff
The filament rheostat in all 20's era radio regardless of "sophistication" was manifold, not only did it reduce the voltage for the filament, provided bias, compensated (manually) for the filament battery drop in use and in some instances is the volume control, further since most 20's circuits were poorly shielded it was a way to reduce any over amplification. Note worthy is earlier tubes had great variation in performance, hence, earlier sets had greater numbers of filament controls, some, had a filament control for each tube. Later, some manufactures got creative and used fixed resistors, often as a length of resistance wire covered with varnished cambric. Such a set would have a "master" battery setting rheostat, more so was the use of a barretter, Amperites, for filament control. In every circuit where the input return connects to the filament determines if a more negative or positive bias is applied. For amps. the return is to the negative filament, generally as the stage is often provided with 90 volts. In early TRFs no additional bias is required when applied to the RF amp. For detectors, this varies on the intent of the manufacturer to utilize a gas detector tube, often the return is positive with high bias developed by the leak in combination with low B+.

Therefore, using 5 volts fixed, as the filament supply denies the "free" bias obtained by rheostat drop, consequently the stage may perform marginally.

Radio fans of the 20's were well aware that the new 201A was a blessing as it could be (hard) rejuvenated, many times before being exhausted. Once a week, it was popular to operated the radio with just the filaments, bright with the B batteries disconnected for an hour. Curiously, it makes me wonder if that is the reason why so many battery harness have such frayed and shortened "B" connections at the battery end...

A radio whose IF is oscillating either has a bad bypass cap, too high an impedance at the "B" source, thus, a bypass cap is needed where none would be with carbon/zinc pile, "A" supply is more the 6.3 volts or it is just a bad layout of adjacent grid/plate buss...

I prefer to operate my sets with a secondary battery of late it has been salvage NIFE battery and either "B" packs of "D"cells or a Majestic "B" supply, sometimes using filament current transfer relay.

YMMV

Chas

_________________
First they ignore you, then they laugh at you, then they fight you, then you win.
"Gandhi"


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Sep Fri 28, 2018 4:45 pm 
Member

Joined: Aug Wed 04, 2010 5:40 pm
Posts: 327
Location: Tyngsborough, Massachusetts
I was only suggesting limiting the A supply to 5 volts for this radio, the Leutz C-7, because the schematic shows the oscillator tube filament connected directly across the A supply terminals, and for radios wired according to the schematic that tube would receive full A voltage which could be over 6 volts. My C-7 has an additional rheostat for the oscillator filament, so it's not an issue, in fact when I tried mine I ran the A supply at about 5 1/2 volts and used the rheostats to control all of the filament voltages. With 5 volts connected to the A supply, you would still have the rheostats for the other 6 tubes to lower the voltage below 5 volts as necessary.

On the Indiana Radios C-7 page there is a copy of an early blueprint for the construction of the C-7, and it seems also to show the oscillator tube filament directly connected to the A supply terminals. The scan is quite small and not of great resolution, so it's a bit hard to read.

Jeff


Top
 Profile  
 
 Post subject: Re: Roaring 20s Superhets
PostPosted: Oct Mon 29, 2018 3:37 pm 
Member

Joined: Dec Thu 31, 2009 4:28 pm
Posts: 4585
Location: Medford OR
I put together a collections of 20's supers:

https://www.russoldradios.com/1920s-sup ... odyne.html

_________________
"I just might turn into smoke, but I feel fine"
http://russoldradios.com/


Top
 Profile  
 
Post New Topic Post Reply  [ 1268 posts ]  Moderator: sofaslug Go to page Previous  1 ... 59, 60, 61, 62, 63, 64  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: U106 and 11 guests



Search for:
Jump to:  
























Privacy Policy :: Powered by phpBB