Testing Phono Cartridges

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Testing Phono Cartridges

Post by John Maxson on Fri Apr 22, 2011 9:43 am

I have a 1947 Silvertone radio/ player. The radio works great but the phono does not put out any sound. I brought a 78/lp cartridge on ebay and hooked it up to an RCA jack and plugged it into the chassis in place of the original line. I get no sound. I also tried plugging that Jack into a modern portable boom box that has an aux jack and got no sound. How can I test the cartridges to get to the source of the problems? I would like to test teh new one and the old 78 one.

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Re: Testing Phono Cartridges

Post by Resistance is Futile on Fri Apr 22, 2011 2:24 pm

They probably used a crystal cartridge, over time they no longer function (Just like crystal earphones). I doubt they are magnetic cartridges-too old for that. May just have to install a newer turntable and use a preamp to work. $$$$
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Re: Testing Phono Cartridges

Post by John Maxson on Fri Apr 22, 2011 5:08 pm

Still need to test the new one I got. It is NOS. Can I replace the crystal one with a modern one?

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Re: Testing Phono Cartridges

Post by Bill Cahill on Fri Apr 22, 2011 8:03 pm

Newer turntable!?
Are you kidding?
How about putting in a decent ceramic cartridge with the correct voltage?
Not all crystal cartridges go bad.
The reason they most often go bad is extreme termperature changes. They especially don't like high temps.
What is the RCA number on cartridge? If it's an old crystal, it may very well be bad, also.
The old cartridge not working is usually because the cartridge has gone bad.
As I said, they hate extreme temperature changes. ESPECIALLY heat.
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I have some 15 yr. old rebuilt cartridges that are still good.
I also have some older crystal cartridges, including two made in the 70's, that are still very much alive. Why?
Because they weren't subjected to high heat.
Attics, garages, sheds, etc., are good examples of bad storage places.

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Re: Testing Phono Cartridges

Post by Bill Cahill on Fri Apr 22, 2011 8:06 pm

There are cartridge rebuilders, by the way.
Not cheap, but, I've had sme rebuilt with great results.
Welcome to the forums....
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Re: Testing Phono Cartridges

Post by John Maxson on Mon Apr 25, 2011 12:12 pm

I found some info on a website. They say that if you touch the cartridge leads together the unit hould make a loud buzz with the volume all of the way up. I tried that and I don't get any buzzing. The radsio does work. Is there a certain tube or circuit component that would be disfunctional even with good radio operation? (1947 Silvertone AM/phono)

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Re: Testing Phono Cartridges

Post by Resistance is Futile on Mon Apr 25, 2011 3:15 pm

Ahh.Now were getting somewhere. Check the phono leads from the cartridge with an ohmmeter. you should get continuity in both leads. If not check to make sure one of the wires isn't broken. check the phono connection(s).
It could be that the phono radio switch needs cleaning or it may be broken. Trace the wire back through the switch, and use caution while touching only the phono connections. This is called tracing the signal. If the radio works then it is definitely a bad connection to the phono. Correct the wire default(s) and you may be surprised that the cartridge still functions. cheers
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Re: Testing Phono Cartridges

Post by Bill Cahill on Mon Apr 25, 2011 3:46 pm

F9rst of all, the information given is incorrect. If you touch the red lead with your finger, with cartridge disconnected, you should get a buzz.
If you do, then, put another finger strongly on the black, or, ground lead at the same time. If the volume of your buzz goes down, that is not your problem.
It is, as stated earlier, your cartridge.
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Re: Testing Phono Cartridges

Post by kb4yrc on Mon Apr 25, 2011 11:10 pm

Bill, You been in the 807's again ? ..... Gregg

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Re: Testing Phono Cartridges

Post by Resistance is Futile on Tue Apr 26, 2011 12:07 am

No I think Bill is referring to the incorrect statement about shorting the phono wires together, that part is incorrect information on the posters interpretation of what he understood he should do.

Bill is correct in stating that just touching the wire while the leads are connected to the radio in the phono position are right. The concept is to introduce hum into the red lead whilst the cartridge itself is disconnected but the wires that go to the phono amp are used. Using your fingers on both the red wire and the return wire at the same time on the second test would indicated if the hum is reduced the second wire is correctly connected to ground, therefore a reduction in the hum should be noticed as the fingers are in part now, acting as an attenuation, redirecting the signal to ground..and showing that wire isn't open.
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Re: Testing Phono Cartridges

Post by Bill Cahill on Tue Apr 26, 2011 12:12 am

807's????
I'm simply saying touch the red, or, insulated wire with your finger. You should hear a hum.
To check wiring, touch both wires at once. Yolu should hear a decrease in volume of the hum..... Correct.. That is exactly what I was saying. Thank you......
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Re: Testing Phono Cartridges

Post by John Maxson on Tue Apr 26, 2011 11:46 am

I will check the connections. One thing I notice is that The printing on the knob is opposite of the direction to turn the knob for each selection.

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Re: Testing Phono Cartridges

Post by kb4yrc on Tue Apr 26, 2011 7:31 pm

I was refuring to Bill's typing skills. ..... Gregg

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Re: Testing Phono Cartridges

Post by Bill Cahill on Tue Apr 26, 2011 8:14 pm

My typing skills are good. I was very tired.
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Re: Testing Phono Cartridges

Post by John Maxson on Wed Apr 27, 2011 8:57 am

What is the difference between ceramic and magnetic cartridges? Which does a late 60's phono take?

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Re: Testing Phono Cartridges

Post by Bill Cahill on Wed Apr 27, 2011 9:51 am

Without knowing more about the phonograph, I can't say.
Ceramic cartridges are faily low voltage.
Magnetic cartridges are electromagnetic, and, have to have an extra pre-amp stage in order to work properly.
If it's a childs' rp, I guarantee it doesn't use a magnetic cartridge.
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Re: Testing Phono Cartridges

Post by John Maxson on Thu Apr 28, 2011 11:44 am

The 1947 Silvertone does humm when the positive lead is touched. When I touch the negative lead, the humm reduces. When I rub my finger across the positive lead, I get the scratch sound through the speaker. So, I would assume that my cartridge is bad. I put a meter to it on the 1K scale and it went up a little. I didn't get a reading off of it.

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Re: Testing Phono Cartridges

Post by Bill Cahill on Thu Apr 28, 2011 8:24 pm

Meters cannot read cartridges, but, I guarantee the cartridge is bad.
You need a crystal cartridge, or, higher voltage ceramic.
How manny tubes in this set?
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Re: Testing Phono Cartridges

Post by John Maxson on Fri Apr 29, 2011 10:47 am

Without looking again I think it has 5 tubes. How much would it cost to rebuild the cartridge? Is it better to put a ceramic one in?

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Re: Testing Phono Cartridges

Post by Bill Cahill on Fri Apr 29, 2011 3:23 pm

That would depend on the cartridge. Personally, I think it's better to get original re built.
There is a companny in Ohio that still does it.
Not sure of cost. Maybe 40.00 with needle, but, don't hold me to that.
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Re: Testing Phono Cartridges

Post by John Maxson on Mon May 02, 2011 11:50 am

I found a site that explains rebuilding by replacing the crystal with a piezo element from radio shack. The element is only $2.00, and will pick one up and try it out.

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Re: Testing Phono Cartridges

Post by bill57 on Mon May 02, 2011 8:09 pm

That sounds interesting, John. So what is the site? Let us know if you try it. I would like to try rebuilding one also if I could find a way to replace the crystal. I have about 8 players now that have bad cartridges so if you find a more economical way to do it that would be great.

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Re: Testing Phono Cartridges

Post by John Maxson on Tue May 03, 2011 9:36 am

I will post the site tomorrow when I can get at teh printout. I brought 2 piezos and took one apart. It looks like an easy fix.

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Re: Testing Phono Cartridges

Post by John Maxson on Thu May 05, 2011 8:54 am

http://www.angelfire.com/electronic2/radiosean/tv/Cartridge-rebuild.htm

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Re: Testing Phono Cartridges

Post by bill57 on Thu May 05, 2011 10:28 pm

Thanks for posting the web site. I will pickup one of these and try it.

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