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 Post subject: Restoring Antique Radio Beginner Question
PostPosted: Jul Sun 31, 2016 9:52 am 
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Joined: Jul Sun 17, 2016 6:27 am
Posts: 22
Hi, I'm just beginning to learn how to fix antique radios, and I'm going to have many questions, but I wanted to quickly ask this one first. I've heard many times online that if you get an antique radio or television or whatever, DO NOT plug it in. Can someone give me an in depth explanation as to why that is? What is the problem in plugging it in? What should I do to the radio before it's safe to plug in? Thanks!

Also, here's another question I just thought of:
If you have an old tube radio plugged in, what are some signs that a tube needs replaced- If a tube goes bad, what will happen? How would I know?


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 Post subject: Re: Restoring Antique Radio Beginner Question
PostPosted: Jul Sun 31, 2016 12:27 pm 
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Joined: Feb Sun 01, 2009 2:56 pm
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Location: Victoria, Australia
Plugging in any device that is powered by reticulated / utility power without knowing its condition, is rather like sticking your head in the output end of a loaded cannon. The wiring in many of theses things deteriorates with the effluxion of time, loose its insulation and become quite dangerous and short: This must be inspected.

Also the likelihood of an early radio not being worked on is quite low and if it hasn't the probability is high that it broke down or was replaced with new technology. There is then the occasional risk that whoever worked on it was a complete ignoramus and after stuffing it up flipped it.

Early sets, including TV, used a waxed paper type capacitor, these became resistors over time, to the point that unless I know a radio with them in it is running in some sort of fashion, it will not be powered.

Then there is the Electrolytic capacitor: Depending a little on its era, it will dry out & become ineffective, or more commonly as it is chemical, the oxide layer within that is essential for it to function is lost. This oxide layer is the insulator and requires a small leakage current to maintain it. When the set is abandoned for a long period and it is lost (looses form) the cap presents as a short circuit, sometimes exploding but invariably has been the demise of many rectifiers & transformers.

Another trap for the uninformed is the "Hot Chassis" & many US & European radios have no transformers & the chassis is connected to that power. There is a 50/50 chance that line /active is on the chassis & that can kill.

It does pay to go through information on this forum and other places to get an understanding of the basics of electricity before attempting any electrical repair. Tubes, I find are not the most unreliable part of a radio.

Marc


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 Post subject: Re: Restoring Antique Radio Beginner Question
PostPosted: Jul Sun 31, 2016 12:35 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
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Location: Annapolis, MD
Most of the time, a tube goes bad by slowly losing emission from the cathode. Depending on the circuit, it can get pretty weak before you notice anything. The symptoms vary widely...from reduced sound volume to distortion-- or simply not working. You know a tube is bad by going through a checklist relating to a particular symptom.

When getting an old set running, the tubes are often not an issue.

Admonition about applying power: Certain components degrade with time and/or storage conditions, and can fail catastrophically when power is applied. The most common example is electrolytic capacitors which fail shorted and burn out the power transformer.

EDIT: Marc and I typing at the same time...some duplication and his is more complete

_________________
-Mark
"Measure voltage, but THINK current." --anon.


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 Post subject: Re: Restoring Antique Radio Beginner Question
PostPosted: Jul Sun 31, 2016 12:55 pm 
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Location: Groveland MA
Here is a great place to help you get started;

http://www.antiqueradio.org/welcome.htm

The beginners section is very helpful, enjoy!

Russ

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A place for everything, everything in it's place. I just don't remember where all those places are.


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 Post subject: Re: Restoring Antique Radio Beginner Question
PostPosted: Jul Sun 31, 2016 2:01 pm 
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radioalfa wrote:
Here is a great place to help you get started;

http://www.antiqueradio.org/welcome.htm

The beginners section is very helpful, enjoy!

Russ



+1 much safer to read this, than plug the unknown set in: With aged electrical stuff, exuberance can kill.

Marc


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 Post subject: Re: Restoring Antique Radio Beginner Question
PostPosted: Jul Sun 31, 2016 2:14 pm 
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Joined: Jan Tue 31, 2012 1:55 am
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Location: Mountains of Mourne. Ireland.
DonColeIII wrote: What should I do to the radio before it's safe to plug in?

Watch these, especially the ones from John Kopp.


Two videos from Rick McWhorter.

AA5 Radio Signal Flow.
http://www.youtube.com/watch?v=zknp0FOkPXU

Signal Flow Transistor AM Radio.
http://www.youtube.com/watch?v=qlx7KRSiPM4


Check-out John Kopp's youtube channel, user name 'joernone'. John has done quite a few repair and restoration series.

Part one of 14. 1941 Zenith Model 6-S-597
http://www.youtube.com/watch?v=SuKWqPjd6gc

Part one of 35. 1936 Philco Model 630B
http://www.youtube.com/watch?v=IelT-Qp13po

Part one of 38. 1935 Atwater Kent Model 145
http://www.youtube.com/watch?v=BNnnqxEo8MA

Part one of ? 1937 Philco Model 37-2670
http://www.youtube.com/watch?v=Q4TCg1CGTNE


John is known here on Arf as 'badrestorer' ... one of life's good guys.

Here is one of his legendary posts.
http://antiqueradios.com/forums/viewtopic.php?f=6&t=115812




Reading a Schematic.

Three drawings, one circuit. (yes, I know, they are transistors)

This is from an article written by Doug DeMaw W1FB an ARRL contributing editor for QST magazine. It appeared in the February 1984 issue.
Search... arrl 8402019.pdf

Image
"Examples of an identical circuit (A and B) drawn in different ways.
The pictorial representation at C is for the circuits shown in illustrations A and B.

This shows how we can relate the drawing to the assembled circuit, which would normally be mounted on a circuit board or a metal chassis."



To save videos for later viewing, use→ http://keepvid.com/ Save at (Max 480p)
Image

Just copy + paste the youtube video URL into the top download box... avoid the advertisements (cleverly named Download) and the offer to install Video Downloader on your desktop.

Welcome aboard :)
Greg.


Edit: images update.


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