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 Post subject: Learning to read schematics - any pointers?
PostPosted: May Sun 16, 2021 7:03 pm 
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Hello everyone, my name is Brian, and I am a long time lurker here who is constantly amazed by the level of technical knowledge and passion for the art of restoration and preservation in these forums. This is my first post here!

Long story short, I was fortunate enough to befriend a very kind man who is willing to teach me the art of television repair with a focus on Predictas in particular. He repaired one of mine for me and in process I became hooked on learning to carry on the skill, so I will be "apprenticing" under him as time allows from my other business.

I am trying to research and understand as much as I can on my own, but there is one area I am stumped: reading and understanding the schematics for any given TV. It looks like a lost language to me and a bit overwhelming!

Do any of you have pointers or resources that i can be pointed to in order to take some of the mystery out of it so I can start knowing what I am looking at? I'd be really grateful! :D :D

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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Sun 16, 2021 8:05 pm 
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It can be a challenge, particularly for servicing vintage electronics because drawing techniques and symbols evolved as the technology matured. Keep reading the forum and look at diagrams other people post to see if you can follow along.

You could consider:


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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Sun 16, 2021 8:20 pm 
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Joined: Apr Sat 06, 2013 2:18 pm
Posts: 639
Location: New Hampshire
First thing is to learn the block diagram for a B&W TV. It should show what each block does &
the the symptoms of when it fails. Its not a schematic but a flow diagram.
Keep in mind with schematics everyone has there own way of doing it. Different layouts & sometimes
symbols. For this reason its best to use Sams Photofacts. Almost all are drawn the same way
no matter who built it.
Keep in mind Predictas are NOT a good set to start with. They brought " COOL" to TV sets
just like Studebaker brought cool to cars. Bottom line is predictas are tough to work on.
Studebakers are not ! If you are young see Starliner, Hawk, Avanti, Speedster. Cool & fast stuff.
For a first set find a 19" Zenith from apx 1960 - 1965 in a metal cabinet. They are almost
immortal & easy to work on, more so than any other.

enuf fer now
73 Zeno 8)
LFOD !


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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Sun 16, 2021 8:25 pm 
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It takes a while to understand that what is drawn and where parts are physically located is often very different. Finding the parts is good practice. If you are replacing capacitors (and resistors), finding and marking each one on the schematic as you replace them is good practice and a good way to check you work as you go.

I'd strongly suggest you start with less complex radios before jumping into working on any TV.

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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Sun 16, 2021 8:50 pm 
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Really grateful for the pointers and suggestions! I should clarify that I will be starting on much simpler chassis than a Predicta. My mentor will be easing me into this with the hope that I can learn enough with guidance and practice to graduate "upward" to more difficult projects once I get my sea legs so to speak. Looking at a Predicta chassis is headache inducing for a person like myself who has a rudimentary knowledge of even what I am looking at.

I will be started on cleaning, soldering skills and identifying components first. At 52 years old this will be like teaching an old dog new tricks, but my teacher is in his 80's and has the patience of a saint thank goodness.

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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Sun 16, 2021 8:52 pm 
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Location: Dallas, TX
There is a vast array of symbols, many you probably wouldn't encounter in a TV but you never know.
Symbols are frequently different outside the U.S. for instance.
Here is a guide to the symbols you might see.
Attachment:
Electronics_Symbols_Handbook_CIE.pdf [1.36 MiB]
Downloaded 14 times


You can think if a schematic like a road map. As was said the arrangement on the schematic most times id different from the physical layout of the parts. Follow the lines.
Now how the parts work is a different subject.
For instance a tube manual (like the ones from RCA) usually will explain the various parts of a tube and some explanation of the purpose.

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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Sun 16, 2021 9:02 pm 
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Notimetolooz wrote:
There is a vast array of symbols, many you probably wouldn't encounter in a TV but you never know.
Symbols are frequently different outside the U.S. for instance.
Here is a guide to the symbols you might see.
Attachment:
Electronics_Symbols_Handbook_CIE.pdf


You can think if a schematic like a road map. As was said the arrangement on the schematic most times id different from the physical layout of the parts. Follow the lines.
Now how the parts work is a different subject.
For instance a tube manual (like the ones from RCA) usually will explain the various parts of a tube and some explanation of the purpose.



Wow this is super helpful! Thank you for this guide. It is a pretty great resource!

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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Sun 16, 2021 9:07 pm 
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xmo wrote:
It can be a challenge, particularly for servicing vintage electronics because drawing techniques and symbols evolved as the technology matured. Keep reading the forum and look at diagrams other people post to see if you can follow along.

You could consider:



Just ordered a copy. Thanks for the suggestion!

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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Sun 16, 2021 9:17 pm 
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I think I learned a lot about schematics as a youngster by reading the ARRL Handbooks. At least in the tube era, they always seemed to draw the schematic logically, putting the components relevant to (for example) an oscillator clustered separately from the buffer amp, which was separate from a final amp, etc.
Commercial schematics sometimes seem to be more focused on cramming parts into a little paper area as possible.


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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Wed 19, 2021 11:01 am 
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Location: Belrose, NSW, Australia
An electronic schematic is a universal language but there are many dialects, accents and styles.

One of the neatest ideas I ever saw was done by Pye in Australia in the 1960s. They drew the T23 schematic so that the page layout reflected the PCB layout, making it so much easier to find things.

I work with, and create, schematics in my job. My pet hate is hierarchical multi-sheet schematics with links between the sheets. I would rather create a very large sheet and put everything on that, if possible. But I appreciate that designs are getting more complex.

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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Thu 20, 2021 12:21 pm 
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irob2345 wrote:
An electronic schematic is a universal language but there are many dialects, accents and styles.



A good description indeed.

It is a lot like reading music. If you are familiar with the language, it makes sense. Though, if you have never seen it before it is nothing more than a confusing array of Hieroglyphics.

But like all things, if you cannot do it and you want to do it enough, you will learn it and after a while, what seems the impossible becomes possible.


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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Thu 20, 2021 6:29 pm 
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I havent been at it that many years myself. I did some radios and still wasnt clear on schematics when I started on a TV. It baffled me for quite a while but Im much better with them now, not 100% but maybe 95-98% of full understanding them.

Besides what has been mentioned, open up whatever tv you are going to work on and randomly select parts of the tv. Then try to find it on the schematic. Do that over and over. Then select parts off the schematic and try to find them on the tv. This is no afternoon job, its many hours. But being able to locate the part on both schematic and tv is half of the battle. It helped me a lot. Good luck!


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 Post subject: Re: Learning to read schematics - any pointers?
PostPosted: May Thu 20, 2021 9:50 pm 
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I think a lot of the confusion stems from the fact that parts drawn next to each other on the schematic may actually be far away from each other in the actual set. You have to learn that, unlike a roadmap, where the roads shown next to each other actually are next to each other, a schematic shows the circuit flow, not the parts placement. A device is make up of different circuits for different purposes. You learn the purpose of the circuit which helps you to troubleshoot and then locate the actual parts to take measurements or replace.

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