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 Post subject: Old vintage symbols for radio diagrams.
PostPosted: Oct Tue 02, 2018 11:05 pm 
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Early radio mfg sure were creative in symbols on diagrams. AtwaterKent draftsmen seemed to decide onwhat symbols should look like.
Tubes with no envelope (wonder how they kept the vacuum in ?) :D
Chokes that looked like a hot plate.
I am not making fun of these early symbol creators, they were being creative since standards had not been in place.


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Last edited by pauls.ironhorse on Oct Wed 03, 2018 4:56 am, edited 6 times in total.
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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Tue 02, 2018 11:16 pm 
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with some, we're lucky to have a schematic at all----tried working on any LA Radios?

I like the ones where the tube elements are buried in the other symbols---you might not even know there was a tube in there unless you already knew it existed.

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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Tue 02, 2018 11:29 pm 
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pixellany wrote:
I like the ones where the tube elements are buried in the other symbols---you might not even know there was a tube in there unless you already knew it existed.


Crosley was good at that. Many of their diagrams are near impossible.

-Steve

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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Wed 03, 2018 12:19 am 
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In the early days of radio, there was no concept of a "schematic".

The closest thing that got published was a wiring diagram.
Those usually tried to show the wires as actually routed on the board.

Standardization arrived in the 1930s and was finalized before WWII.

- Leigh

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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Wed 03, 2018 12:30 am 
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Because most radio technicians are moonlighting and their real jobs were blacksmiths or motorcycle mechanics. Schematics were often drawn with a mix of symbols many of which were more of a representation of the part. Such drawings were known as diagrammatics...
The "radio fan" magazines of the 20's often used diagrammatics to help the fan build the radio in the article. These circuits were quirky at best and parts placement was critical.. .

I would like to see a Radiola IV or VII redrawn.

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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Wed 03, 2018 12:51 am 
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Howard Sams redrew schematics to their standard notation for consistency.

-Steve

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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Wed 03, 2018 1:18 am 
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No wonder I never seem to find an early radio that was built exactly to the schematic.


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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Wed 03, 2018 1:18 am 
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You would have thought, though, that wiring schematic diagram type drawings were already standardized for electrical work by then. I would have thought by some time in the 1890s that electrical circuitry might have been somewhat standardized and thus leaving for radio the task of representing the new parts that were not used in electrical work such as tubes and variable capacitors. Electrical industry should have had fixed condensers and inductors or transformers, etc. by that time. I would be surprised if electricians at Westinghouse or GE had only some kind of weird haywire gimmicky diagrams at the turn of the century. Am I wrong?


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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Wed 03, 2018 1:23 am 
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Tube diagrams as seen on early schematics. 1930s
Image
from... RCA Handbook for Projectionists. Second edition.

Greg.


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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Wed 03, 2018 5:34 am 
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pauls.ironhorse wrote:
Early radio mfg sure were creative in symbols on diagrams. Atwater-Kent draftsmen seemed to decide on what symbols should look like.
Tubes with no envelope (wonder how they kept the vacuum in ?) :D
Chokes that looked like a hot plate.
I am not making fun of these early symbol creators, they were being creative since standards had not been in place.
Yeppers, the 25L6 in the example is void of its beam forming plates see:
https://en.wikipedia.org/wiki/25L6

The '24a is also known as a screen grid tube, in which a grid or screen is on the outside of the plate, actually it is, some early examples of the tube have grid wire construction for the "screen". Purpose is to provide some sort of shielding but I can't remember a 24a that didn't have an external shield outside the tube as well...

As for hot plate chokes, that is to indicate that it is a flat, pancake choke and which end is the start winding...

Seems to make sense :roll:

Wet electrolytics are often represented by a cup with a "saucer" inside. That is a clue to the fact that the circuit is prone to surges, wet electrolytics are very tolerant of a short period of time with higher than normal voltage, usually during set warm-up.

A variable condenser symbol with a curved plate and arrow indicate which side is the rotor.

I kinda like the old school schematics, they told a story of not only hook-up but of component selection and orientations.

I never could do band switches :?

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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Wed 03, 2018 4:34 pm 
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Couple more. One shows (as mentioned above) the cup or bowl shaped electrolytes.
The other shows a 6G5 magic eye. Someone on Ebay once listed this as a seeing eye.


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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Wed 03, 2018 4:58 pm 
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Now here is a schematic that is really strange. AC Dayton Navigator
I need to remind myself that these schematics are hand drawn probably by a draftsman who had no idea what he was drawing, just working from hand sketches or notes from the designer. I once had to ask a draftsman not to rearrange my circuit drawings with his artistic license. He asked if they were electrically correct, yes but they are hard to understand and not standardized to what other engineers and techs expect.


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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Wed 03, 2018 5:26 pm 
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The AC Dayton Navigator is what is called a "Technidyne" circuit.
It was patented by Lester Jones who offered Technidyne licenses.
Sparton as well as AC Dayton, Continental (Slagle) Apex and Ferguson signed up to make them.

This was mostly an effort to bypass an RCA license.

In the Technidyne, all tuning is done first through a 4 section tuning circuit.

This is fed into a broadband RF amplifier.

The coils in the amplifier are bifilar wound and indeed wound one way then reversed and wound the other way.
Four times on the detector coil.

When I first saw this crazy idea, I was skeptical as to its performance, but once I got my first Sparton Equasonne working I was pleasanly surprised!

It was one of the main reasons I started collecting Sparton radios :D

-Steve

EDIT: here is the patent 1779881A

https://patents.google.com/patent/US1779881A

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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Wed 03, 2018 10:30 pm 
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Thanks azenithnut
Some really strange and creative designs in the early days of home radio receivers.
Speaking of patents, I can remember tube boxes had dozens of patents listed, I often wondered what some of these were Most were probably not even related to the particular tube contained..

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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Thu 04, 2018 3:43 pm 
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Regarding the 25L6GT without the beam-forming plates....

This actually is something that vexes me about modern tube basing diagrams. That is, the specific symbol for beam forming plates was "standardized" to be the same as the symbol for a grid. So, it is not possible to differentiate between beam power tubes and true pentodes, just by looking at the basing diagrams. For example, look at the modernized version of basings 7AC and 7S. 7S was the original pentode basing and 7AC was the original beam tube basing.

Late in the game, the industry muddied the waters by registering some beam power tubes like the 8417 as having 7S basing.

Of course there is nomenclature confusion too... "Beam Power Tube" "Beam Power Tetrode" and "Beam Power Pentode" are synonymous.


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 Post subject: Re: Old vintage symbols for radio diagrams.
PostPosted: Oct Thu 04, 2018 6:33 pm 
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pauls.ironhorse wrote:
Speaking of patents, I can remember tube boxes had dozens of patents listed, I often wondered what some of these were Most were probably not even related to the particular tube contained..


Thanks to Google patents, you can look them up to see what they are about! :D

-Steve

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