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 Post subject: Victor Credenza Induction Motor Coil Rebuild
PostPosted: Sat Feb 10, 2018 3:04 pm 
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Victor Jr
Chappy
Joined: Sun Jan 14, 2018 11:09 am
Posts: 2
I have a Victor Credenza X 1926. It has the electric induction disc motor. I am rebuilding it. I started by re-wiring the exterior wires with 14 gauge stranded THHN wire. When I really got into taking a close look at the wiring of the coils, I concluded that I needed to rewind the coils. Insulation crumbled and the whole thing had a barbecue odor to it. I removed the coils to take a look and now need to decide how to do this. It appears the magnetic wire is combined with a silk insulation. However, I am re-wiring with all modern wire. What I am considering using for the winding is 14 gauge enameled magnetic copper wire. Would I be correct to use the same gauge wire as in the rest of the motor? I am not going to put the silk in at all as the wire is enameled so I assume that provides the insulation between coil wires so they do not short out and burn out the coil. Would that be correct?

Someone in a small magnetic motor group on Facebook suggested measuring the length of the wire I remove in order to get the correct number of windings as the voltage coil and the lower coil will have a different number of windings. This will cause the eddy currents to flow continuously and then in turn cause continuous rotation as the poles attract and repel each other. However, does anyone know what gauge wire was used? I checked the RCA service notes for 1929 and they list an induction motor, but the cycles and voltage were different for three different types of induction motor offered by RCA Victor after RCA bought the Victor Talking Machine Company. With three different voltages, I assume three different gauges of wire and a variation in the number of windings around the bobbin. Just stuck on the gauge.


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 Post subject: Re: Victor Credenza Induction Motor Coil Rebuild
PostPosted: Sat Feb 10, 2018 6:28 pm 
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Victor III
Joined: Thu Sep 25, 2014 4:25 pm
Posts: 554
Location: North Central Iowa
There used to be an old electric motor guy that I delivered to 25 years ago and I asked him about one of those motors and he just said he hadn't seen one in years! I had a run capacitor go out on a phonograph motor last year and Mr. Knorr is dead now, but a different guy runs the shop. When I asked him about re-winding those motors he just said it's almost impossible to find anyone that will do it now because there's so much more money to be made on re-winding large electric motors and the little one's are almost as much work because of how small they are. But the coils on those induction motors are a lot different than a regular motor.

The motor on my 10-70 was getting hot and didn't have much strength (it would bog down sometimes during loud passages of music) and last week I was fussing on it and did find that one of the supply wires at the plug under the motor-board had almost all the strands broken at the screw except two for some reason, so it must have been starved for electricity. I fixed that, and it's running a lot better now. I think I'm going to have to replace one of those things with a good one eventually, and I am going to put a capacitor on it. They did that on the later motors and those motor seem to be stronger as a result. Those motors do run kind of hot, but the motor in the 10-70 is the only one of mine that does make a noticeable smell after it's been running for about half an hour. I've felt those coils when it's been running a long time, but I can't tell that any one of them is hotter than the others. The insulation on that wire does not seem to deal well with dampness, and this 10-70 of mine was in a damp basement for a long, long time before I got it.

Well, good luck with that project. Hopefully you won't have too much trouble getting it sorted out. I wish I were more help though.


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 Post subject: Re: Victor Credenza Induction Motor Coil Rebuild
PostPosted: Sat Feb 10, 2018 6:42 pm 
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Victor Jr
Joined: Sun Jul 30, 2017 5:28 pm
Posts: 29
Location: Deltona FL / Brampton ON
Did you measure the resistance ( Ohm) of each coil. With my limited knowledge I would imagine that you will need to use a length of wire to give you close to this resistance value otherwise with a lower resistance the motor would draw more amperage and run hot.
I believe I have one of these motors in my attic. Not sure what condition it is in but will have a look.

Herman


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 Post subject: Re: Victor Credenza Induction Motor Coil Rebuild
PostPosted: Sat Feb 10, 2018 7:16 pm 
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Victor Jr
Joined: Sun Jul 30, 2017 5:28 pm
Posts: 29
Location: Deltona FL / Brampton ON
I brought the motor down from the attic. The coils measure 9-Ohm each side so I am assuming both sides uses the same gauge wire then the number of turns on each coil will be equal.

This chart should help to determine the length of wire required to achieve the 9 Ohm resistance. 14 gauge in my opinion would be too thick.

I measured the wire dia. of the coil and reads 0.0480


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 Post subject: Re: Victor Credenza Induction Motor Coil Rebuild
PostPosted: Sun Feb 11, 2018 8:46 am 
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Victor Jr
Chappy
Joined: Sun Jan 14, 2018 11:09 am
Posts: 2
Thanks for the information. I had wondered about 14 gauge being to thick. The info on resistance and the gauge chart will help me a lot.


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 Post subject: Re: Victor Credenza Induction Motor Coil Rebuild
PostPosted: Sun Feb 11, 2018 9:31 am 
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Victor Jr
Joined: Sun Jul 30, 2017 5:28 pm
Posts: 29
Location: Deltona FL / Brampton ON
Chappy wrote:
Thanks for the information. I had wondered about 14 gauge being to thick. The info on resistance and the gauge chart will help me a lot.


Good luck and remember to ensure you wrap the iron core with insulation paper before winding the coils and also to spray your windings with insulating varnish. This will prevent the vibrating coils from shorting out due to friction.

16 gauge would require approx 2200ft per coil
18 ------------------------ 1400ft

You may need to make a jig to hold the core bar so you can rotate it at a workable rpm to wind the coils. Also suggest making two side insulators to fit over the square core to create a form for the sides of the windings.


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 Post subject: Re: Victor Credenza Induction Motor Coil Rebuild
PostPosted: Mon Feb 12, 2018 2:35 pm 
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Victor IV
Joined: Mon Aug 24, 2009 3:08 pm
Posts: 1742
Location: Harrison Township, MI
Why don't you just measure the diameter of the existing wire that you want to replace? Use the same gauge/diameter and calculate the length to give the same resistance. The other option would be to accurately weigh the motor frame, or coils themselves, with & without its windings. You can equate the coil length from that. The actual number of turns is most likely not super critical, but getting each coil the same will be! Have you also considered that these motors probably are not that expensive to buy?


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 Post subject: Re: Victor Credenza Induction Motor Coil Rebuild
PostPosted: Mon Feb 12, 2018 5:39 pm 
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Victor Jr
Joined: Tue Jun 02, 2009 10:19 pm
Posts: 25
Jerry’s recommendation to replace the pair of coils from a donor motor is a good suggestion. The motors are very plentiful and not expensive. I suspect someone like George Volema has a trunk load of them. If you want to rewind the coils for the challenge then that is another matter altogether. The wire diameter, length and number of turns are critical, it will be tricky to wind this neatly by hand, if not neatly wound the wire length and number of turns will not work out right even if you get the overall coil resistance right. Also, be aware that there are six coils all together. If you are careful to unwind and count the turns and measure the wire gauge and length you might have a chance of being successful. Also, know that there are three different coil types (Type 1, 2 and 3) depending on the frequency of the AC line and the application of the motor. Fortunately the one you need, Type I is the easiest to find. The 10-70 motor is a Type 3 as the automatics use a heavier duty motor so don’t use the resistance readings from that. The motor frame often has a plate with the motor type but the coil may not be marked.

Are you sure you want to do this? Your objection to the bar-b-que smell does not necessarily make the coils bad!

Mark


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 Post subject: Re: Victor Credenza Induction Motor Coil Rebuild
PostPosted: Tue Feb 13, 2018 2:59 pm 
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Victor IV
Joined: Mon Aug 24, 2009 3:08 pm
Posts: 1742
Location: Harrison Township, MI
Chappy,

Mark is correct, "Your objection to the bar-b-que smell does not necessarily make the coils bad!".

These motors are kind of smelly even when they're fine. Have you tried running the motor for a length of time to see if it heats up, (excessively), or smokes? The one in my 8-4 will start to smell a bit after playing for a while, but it doesn't smoke and doesn't get overly hot. Just the scent of age I guess. Still, I never run it unattended and I never leave it plugged in when not in use.


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 Post subject: Re: Victor Credenza Induction Motor Coil Rebuild
PostPosted: Tue Feb 13, 2018 8:44 pm 
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Victor O
Joined: Sat Jul 05, 2014 2:26 pm
Posts: 53
Location: North central Oklahoma
As others have said, smell doesn't necessarily mean bad coils. If you don't know already, there is a trick called the dim-bulb test, where you put a light bulb in series with the motor and plug it in. Google search dim bulb tester and you will see you can easily build one You will need a cord, two light sockets, and a light socket to outlet adapter, or just use an outlet in place of the second socket. The diagrams will show that you wire the light socket in series with one of the power leads to the outlet. Put a 25W incandescent bulb in the light socket and plug it in. If the bulb glows at normal brightness, it is shorted out. If it glows dim, you are probably OK. Go up to a 60W then 100W bulb. If you can find a 200W bulb, motor will probably operate normally.

If everything checks out OK, take the coils off and clean all the dust off of them real good, use compressed air and a clean paint brush, then use a brush and clean them with mineral spirits and dry them off with compressed air and let dry for a couple of days. Get some spray-can electric motor varnish (get online at Grainger) and spray the coils. Use the clear so it does not change appearance of coils. You can do a couple of coats if you like, 2 to 3. Let dry a couple of days then reassemble.


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