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Philco magnetic cart help
OldRestorer
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#1

03-01-2017, 10:53 AM
Ok,
 I dont know where this goes mods...
 I have a buddy who messed with the original magnetic cart in his 48 Philco D-10 phonograph.
All I have now is a cart with 4 loose wires.. Can anyone help me to figure out what wires go where?


Thanks, 
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morzh
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#2

03-01-2017, 11:04 AM
Are there any perm magnet in it?
If not, then there might be two coils: one is creating magnetic field and one is the small moving coil attached to the needle. Same principle as in the speaker with field coil.
If this is the case, then you should have two wires with continuity and two other wires also with continuity, with no continuity in between the two pairs.
If this is the case, then I would guess that the larger resistance is the field coil (probably is fed with a DC voltage) and the smaller one is the output (goes to the amp's input).

Now this said, I have no idea what I am talking about so treat it as such.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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OldRestorer
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#3

03-01-2017, 12:53 PM
It is a magnetic cart and there is a coil around the needle holder.
He said it worked but he screwed it up.
How would I check the resistance?
Do I set the meter to a low resistance and then put the red on the wire and the other to the cart itself?

There are 3 divits in the separator board so I was thinking there were 3 separate wires and one would be ground but I have a picture of one from online and there is no third wire... It is a Mono cart so I cant figure out how the darn thing would use 4 wires for a 2 wire connection...
I have tried a bunch of combinations but nothing so far...

Ugh...

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Times I have been electrocuted in 2021
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Last year: 6
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morzh
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#4

03-01-2017, 03:25 PM
Put it on low ohms. It is a copper wire so the resistance will be between hundreds of ohms and a few kOhms.

4 wires - if my theory is correct, two separate coils have 4 wires, 2 for each.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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Mondial
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#5

03-01-2017, 04:15 PM
Morzh, it does look like there are two coils. 

One coil is the actual moving coil and the second is probably a hum cancelling coil. They are connected in series with the center common connection going to ground. So there are only three external connections. 

The question is how to phase the two windings for the desired hum cancellation?

There is a detail of the pickup windings and connections to the associated impedance matching transformer on page 17 of the schematic here:

http://www.nostalgiaair.org/pagesbymodel...013623.pdf
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morzh
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#6

03-01-2017, 05:42 PM
(03-01-2017, 04:15 PM)Mondial Wrote:  The question is how to phase the two windings for the desired hum cancellation?

That is easy: since the only effect of reversing polarity is hum, then if it hums, reverse the humbucking coil.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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Mondial
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#7

03-01-2017, 06:14 PM
Yes, but he has to test it before he reassembles the whole cartridge.

That is, unless he doesn't mind taking it all apart again to try the reverse polarity.
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OldRestorer
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#8

03-01-2017, 09:56 PM
I have put together and pulled apart 10 times...

I am getting really tired of working on it...
Times I have been electrocuted in 2021
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AC: 4 DC: 1
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morzh
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#9

03-01-2017, 09:56 PM
Kirk? Sure he doesn't!
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