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 Post subject: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Wed 30, 2020 5:11 pm 
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Location: Columbia, SC USA
I am considering purchasing a Zenith Clock Radio J733. The clock works, but the radio does not. I'd like to restore the radio as it would go well with my midcentury furniture.

I have watched youtube videos on restoration, and I understand I have huge knowledge gaps. This will likely be a long term project as I learn how to safely diagnose things and repair. I don't know yet if this will be a single project, or if the bug will bite and this will become a hobby.

I have gathered I need a multimeter, an oscilloscope, a signal generator, and isolation transformer, and a variac(sp?) limiter.

Can any of you recommend a budget friendly way to get started? Can an inexpensive portable multi/scope do some of what I need? Are the generator, transformer and variac limiter expensive? is their other equipment I need? or should I give up now. :)

Thanks for any advise as I consider setting out on this expedition.

David


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Wed 30, 2020 6:32 pm 
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Location: Mountains of Mourne. Ireland.
You don't need an oscilloscope for fixin' radios, It's just a fancy visual multimeter.

For many years all I had was a multimeter, soldering iron and pencil & paper.

Greg.


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Wed 30, 2020 6:44 pm 
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The test equipment items are just tools by which to gather information, or generate signals. Unless you know how to use them, they are pretty much worthless.

The Archives section of this site has a good "how to do it" series covering the fundamentals of radio servicing.


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Wed 30, 2020 6:48 pm 
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Location: Austin, Texas
If you haven't bought a multimeter, I would recommend that you look for one that includes a capacitance function with a low range of around 200pF.

To do alignments, you will need a signal generator with a range of 200KHz to 2MHz for AM radios. Up to 30MHz may be needed for short wave radios.

Jay


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Wed 30, 2020 7:21 pm 
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Jay,

The radio I'm looking at has FM too. Do I need something different to align FM?

D


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Wed 30, 2020 7:23 pm 
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tgr131 wrote:
I have gathered I need a multimeter, an oscilloscope, a signal generator, and isolation transformer, and a variac(sp?) limiter.
David, the BEST thing you can have is the knowledge on how to operate whatever you have. And how do you acquire that? By using it with a radio that is already working so you know what proper operation looks like and how to recognize "OK" when you see it.

I wish I had a dollar for every time someone has said on here, "I have an oscilloscope, but I have never used it."

It's kind of like what they used to say about Treasury Agents recognizing counterfeit money. They don't study counterfeit money, they become vary familiar with the REAL money so that they recognize when something isn't right.

The other thing is knowing Ohms Law and the Power Equations. You can either remember all of these, or if you are ok with algebra simply know how to transform one equation into the others.

Ohms Law (all three versions)
E= I X R
R= E / I
I= E / R
Where E is the voltage (Volts) across an element (typically a resistor), I is the Current (Amps), R is the Resistance (Ohms).

Power Equation (all three versions)
P=E X I
P= I(squared) x R
P = E(squared)/R

Where P is power (Watts).

If you know these things you can always tell how much current is flowing through a circuit by simply measuring the voltage and resistance. You will also know if a resistor is being stressed by too much power by just measuring the voltage and either measuring or knowing the resistance. It helps if you know this stuff rather than always having to ask someone and never knowing how/if they gave you the right answer (what wattage resistor do I need for..., how much current is being used by this tube..., etc.).

The other vital piece of test equipment is you! You would be surprised how many times I (and others) have identified a problem just by "looking, listening, or smelling" a radio (yep, smell). Visual inspection can catch a lot of things. It is also good to understand the ability to describe what you are experiencing (hum and buzz are too different things and neither of those is static, and all differ from the sound of a bad/intermittent connection). Burned resistor has a distinctive odor. Burned Selenium Rectifier does also (rotten eggs). Burned transformers also have a distinctive smell (hard to describe, but once you have smelled one you won't forget what it is like - burned enamel insulation). Overheated resistors show the signs of heat induced discoloration (discolored, swollen, cracked).

You already have everything you need. Just learn how to use it. Watch videos (my standard recommendation for Joernone, John, Badrestorer https://www.youtube.com/playlist?list=P ... 0EC75273C1 ). Try things out on a working radio (preferably tube not transistor). Make the mistakes that will be made with something that is not important to you (not your grandfathers first radio that is priceless).

One more thing. Walk before you run and take your time (this is not a race). Make sure you know how to deal with an AM radio before you get into aligning an FM radio. Then make sure you understand the alignment procedure before you get in too deep. Try to identify your starting point so that you can return to that if all else fails (been there when I accidentally turned the wrong thing).

This was probably more than you want to know, but you just happened to catch me in that kind of mood. :-)

Best of luck.

Curtis Eickerman

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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Wed 30, 2020 7:37 pm 
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Eickerman wrote:
This was probably more than you want to know, but you just happened to catch me in that kind of mood. :-)

Best of luck.



Curtis,

Thank you for your kind words and encouragement!

David


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Wed 30, 2020 7:41 pm 
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Location: Mountains of Mourne. Ireland.
Ohm's law.
Image
Place your finger on the one that you want to find.


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Wed 30, 2020 7:45 pm 
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tgr131 wrote:
Thank you for your kind words and encouragement!
You are welcome. Oh, and take the time to learn how to read a schematic (the video series I pointed to can help). Trying to work on a radio without being able to understand what a schematic is trying to tell you is like trying to cross the United States without a roadmap (GPS or paper).

Understand that a schematic is not a wiring diagram and visa versa. They both have their uses, but the schematic is priceless when working on a radio. It will help you to know what is hooked to what and it will help others to guide you in the right direction when things are not making any sense (we've all been lost in a radio where we have run out of ideas).

Again, I wish you all the best in your endeavor.

Curtis Eickerman

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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Thu 31, 2020 1:21 am 
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Joined: Mar Wed 16, 2011 10:44 pm
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Location: Peekskill, NY
What does a novice need to do any new undertaking?

1) an inquisitive, perservering mind.

2) the internet.

3) a credit card.

I think you have all three, my friend.


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Thu 31, 2020 2:06 am 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3610
Location: Dallas, TX
Spend some time at this website.
https://www.antiqueradio.org/howfix.htm

One skill that you will have to learn is how to solder. There are a series of videos. practice makes perfect.
https://www.youtube.com/watch?v=vIT4ra6Mo0s

I would recommend (lowest investment);
soldering iron and supplies,
de-soldering tool,
multimeter DMM,
analog meter (one with a needle dial) this is much better for adjusting,
dim-bulb tester (rather than a variac and ammeter),
set of NOS tubes for that radio,
schematic and service info,
accurate RF signal generator (400KHz to 110 MHz, with modulation capability) you possibly could get by with one just covering 455KHz and 10.7MHz (the IF's) and use local radio stations to adjust the tuning range.
If you remember to never touch the radio when it is plugged in and also out of the cabinet you could get by without an isolation transformer.

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Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Thu 31, 2020 2:14 am 
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Joined: Jan Tue 10, 2012 8:39 am
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That last statement is in error. Please add that your test equipment needs not to be connected either.


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Thu 31, 2020 2:28 am 
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Joined: May Thu 14, 2015 4:15 pm
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Location: Dallas, TX
bob91343 wrote:
That last statement is in error. Please add that your test equipment needs not to be connected either.

I guess it somewhat depends on the test equipment. Good point, but many times a couple of isolation capacitors will decrease the danger caused by the equipment grounding.

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Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Thu 31, 2020 2:49 am 
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Well you can do that if you like but I don't think I would want to use capacitors to isolate the power line from my precious self.


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Thu 31, 2020 7:11 am 
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Joined: Dec Sat 28, 2019 4:18 pm
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Location: Corinth, TX
And Yet More Advice:
First, define the problem. You are not just restoring an old radio. You are repairing AND restoring an old radio. That implies repair before restoration, BUT with old radios, you have parts (primarily capacitors) that should be replaced before you start working.

And that means you should develop more than just rudimentary soldering skills, component identification, and schematic reading.

For AM radios, you do not need an o'scope. All you should need is a pretty good modern DMM with a bar graph display and a dim bulb tester. A 3 - 5 amp variac (OK, a variable transformer) would be handy. "Variac", like "Scotch" tape, is trademarked. Also, a working signal generator. I say working, because as a newb, you probably do not want to develop skill repairing test equipment also.

A contrarian opinion, perhaps, but I am ambivalent about isolation transformers. If you are careful, you do not need one. Used improperly, they can give you a false sense of security.

My recommendation is to find - and repair - an AA5. That is an All American 5: a simple, cheap, 5 tube, AM receiver. They made 100s of thousands of them in the '50s and '60s. If you destroy one while learning you will not have lost much. Your J733 is a keeper, right.

FM is a little more difficult, especially to align.

I also recommend that you find a '60s ARRL Handbook. You should be able to find one in a used bookstore or a hamfest for no more than $5 or so. It will be a good basic and intermediate level book covering electronics and radio theory.

John


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Thu 31, 2020 7:31 am 
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Joined: Jan Tue 10, 2012 8:39 am
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Variac was originally a trademark owned by General Radio but it has long expired. Now people toss around the word variac as though it's just part of the language. Which I guess it has become. It's made up of variable ac.

I have one of a different brand that has marked on the panel that it's protected by US patent. I looked up the patent and it's an original one from an engineer at General Radio, not the company that had it on the panel. It covered the mechanism by which a carbon brush shorted adjacent turns of the winding without causing excessive current. That was necessary to avoid having the load disconnected when you turned the knob.

An old tube type clock radio is probably similar to an AA5 or maybe only four tubes. As cheap as they could make it. Very easy to repair. An isolation transformer is a good idea but you can do without if you are careful. First make sure the tubes light.


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Thu 31, 2020 8:58 am 
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A simple reminder can be your best tool.


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Thu 31, 2020 5:09 pm 
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Joined: May Thu 14, 2015 4:15 pm
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Location: Dallas, TX
While we are talking about safety.
https://www.youtube.com/watch?v=3s7T_ShJ7Ao

I hope we don't scare the OP off.
My suggestion that an isolation transformer might not be necessary was because he was unsure that he would ever do another radio. I use an isolation transformer all the time. I also have a metered variac that I frequently use. I don't think I ever used a dim-bulb tester, but they are cheaper than a variac with meter. By using a coupling coil on the output of the signal generator, a VOM, battery powered DMM and of course non-metallic adjustment tools, safe troubleshooting and alignment is possible.
According to Radio Museum this radio has seven tube plus a selenium rectifier, so not one of the simplest radios, and is from the 1950's.
It is a hot chassis.

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Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Thu 31, 2020 6:15 pm 
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Thank you for all the feedback, and you're not scaring me off -- just instilling a well founded respect for safety.

I've accepted that this is going to be a slow project for me, as I need to gain a variety of skills and understanding.

The radio's seller has already scared me enough, as she tried plugging the radio in, and said the cord sparked, so she "helpfully" replaced it, :shock: , and tried to replace a bulb that lights up the dial. Sounds like I've picked a complicated project to cut my teeth on, and she might have just complicated it more.

Thanks so much for all of the advice.

David


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 Post subject: Re: Newbie - What equipment do I need to restore a radio
PostPosted: Dec Thu 31, 2020 6:23 pm 
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I have read about the dim bulb tester mentioned above. Would I be correct in thinking this will not work with LED bulbs -- I need to find the old style incandescent?

Thanks!

D


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