Fixing an electric magnetic compound sine plate

[ErichKeane]

So I bought this magnetic compound sine plate on ebay, advertised as not working. I took the risk and ordered it anyway, as a smallish compound sine plate will come in handy on the surface grinder.

I pulled it apart to clean it, and confirmed it didn't work. I pulled apart the electric access panel and saw that there were some messy wiring, and some that were not attached.
So I thought I had my problem!
I pulled theeexisting wiring and ran a new source.

According to the data plate, for 110v I want one of each wire color connected to each line in. (They call it black and red, I clearly have black and yellow...).

I stripped back enough of each wire to get to no-longer crumbly bits, and confirmed with a multimeter that it made sense.

Resistance between the wires was the same, black to black and yellow to yellow were both 2.08k ohm. Crossing colors was "open". My guess is there are two magnets, one with 2 yellow wires, 1 with 2 black.

However, when wired up, it still doesn't cause any magnetic force at all! Does anyone have any guesses as to what I could try?

I checked with a multimeter, my plug has 1.04k ohm resistance, which seems right for two sets in parallel.

 

[ErichKeane]

So also of interest.

If I hook up only 1 color and have the top plate off, I get enough force to barely hold my pin punch in the air at a 90 degree angle(but only if it goes from a center plate to the edge).

If I hook up both, I no longer have enough power.

I put the top plate back on, and can't get enough force to hold anything, but the forces show up on magnetic paper. One or both colors doesn't matter, it still seems to show up lightly.


EDIT TO ADD: Now that I'm googling, I see this similar sized chuck: https://www.ebay.com/itm/273760546002?hash=item3fbd666cd2:g:cTEAAOSwLcNcikvp
Its data plate says 110v and 8W. Based on my resistence, 1 coil should be ~7 watts and both coils is ~14 watts, neither of which seems outrageous. So I guess it makes me think the coils are roughly correct/not incredibly degraded?

 

[markba633csi]

Erich: You may need to reverse the leads of one of the coils since they may be out of phase and fighting each other. You want them to be "boosting" rather than "bucking"
It does seem like the resistance should be lower but I'm not an expert on these
-Mark

 

[ErichKeane]

Erich: You may need to reverse the leads of one of the coils since they may be out of phase and fighting each other. You want them to be "boosting" rather than "bucking"
It does seem like the resistance should be lower but I'm not an expert on these
-Mark

I just ran out to give it a try, but it seems to have made no difference sadly. I thought you were on to something

 

[JimDawson]

Pretty sure that needs to run on DC, AC current would turn it into a demagnetizer. Just a diode in-line should do it.

 

[ErichKeane]

Pretty sure that needs to run on DC, AC current would turn it into a demagnetizer. Just a diode in-line should do it.

I'll say... that makes a lot of sense. The machine itself says it is either 220v or 110v input, but there does not seem to be a diode inline (the multimeter shows the same voltage drop in 'diode' mode in both directions). The seemingly-factory cable I was using also didn't have any inline-diode based on the same measurement. I wonder if this thing EVER worked? I see a decent amount of these types of devices seem to come with some sort of 'box', which I wonder if is just a bridge-rectifier in a box.

I don't have any diodes around that could handle this voltage unfortunately, but I'm going to my buddy's house tomorrow, and he might have something. Presumably I'd want to get a bridge-rectifier eventually, right? I was hoping there would be one I could splice into the center of the wire, since there is no where else to put it, but I don't see online anything like that.

Does that exist, or am I dreaming of that? Presumably I could combine it in a box with a switch if I cared to...

 

[markba633csi]

Yes it may originally have had a bridge rectifier. You want one rated at about 1 amp at 600 volts. They are available on Ebay for a couple bucks or less
You can also make one from four individual diodes like 1N4007 type

 

[ErichKeane]

Yes it may originally have had a bridge rectifier. You want one rated at about 1 amp at 600 volts. They are available on Ebay for a couple bucks or less
You can also make one from four individual diodes like 1N4007 type

I ordered one on amazon that is 50A at 1000v (though the reviews said its likely way less than that). I also ordered a waterproof inline 'junction box' that I'm going to try to put it in. Hopefully thats enough to make it at least somewhat reasonable of an install.

I don't need a switch, there is one on my surface grinder's control panel that controls the 120v AC outlet.

I ordered: https://www.amazon.com/gp/product/B07H5KNR3D/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
and

Amazon.com

 

[Nutfarmer]

Sounds like you are missing the control box. All the electric magnet chucks I have seen have a control box ( power supply).Jim Dawson spotted the problem that it needs dc to to operate properly.

 

[ErichKeane]

Sounds like you are missing the control box. All the electric magnet chucks I have seen have a control box ( power supply).Jim Dawson spotted the problem that it needs dc to to operate properly.

I'm glad you think so too! I see that about 2/3 of these electro magnetic chucks have one.

The fact that the wiring plate has the voltage wiring diagrams on it AND that it has a standard 2 prong outlet on the end of the wire (though, with an odd junction in the middle) made me think it didn't need a control box.

In retrospect (and spending some time with a multimeter) I'm pretty convicted you guys are right. The seller couldn't get it to work either, so I assume 1 of 2 things:

1- The control box used the same plugs on both sides and was disconnectable. When going through the pile wherever they got it, they didn't find the control box, but DID find both sides of the wire. The plugs fit, so they figured it was right. I didn't think about this because the plug in the middle was labeled for 120v and 240v, so I thought they might have just shipped with swappable "ends". But having the box need to be in the middle makes sense too.

2- the last person to have it work had removed the control box because they had a source of DC power on their grinder/mill and just wired this in to that, then proceeded to lose the control box.