I found a new problem with my DoAll surface grinder. The chuck has very little holding power. I suspect a problem with the controller. Thing is I don't know very much about it. And there is no info available for it. The tag says voltage is 24 volt DC and 240 volt AC. The machine was wired for 440 and I am switching it to 220. I have switched the taps on both of the transformers in the controller. But I don't know what kind of voltages to look for and at which taps. I also don't know if I should be looking for AC or DC or where to look. And I have been looking for a new controller ; they have voltage rang from 0-100 volts DC but since I don't know for sure what my chuck is rated for I don't know what to buy. I don't want to buy a controller that puts out 100 volts DC and if my chuck only handles 24 volt DC and smoke my chuck. I think I'm a little over my head with this. Any help and info greatly appreciated...Barry
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Does anybody have a DoAll selectron LV-24 controller
- Thread starter Barry 16"
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Here is what the controller looks like inside. Like I said, I don't know where it should have AC or DC voltage and how much. I will start poking around in there today with tester. The pics show the transformers wired for 440; I have already changed the jumpers for 220 H1 to H3 and H2 to H4 on both transformers.
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eKretz
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Wow, tube rectifiers. Got a photo of the end of the cable that goes to the magnet and where it's connected so we can see a breakout of the wires?
So today I discovered that the taps on the transformer with the red jumpers are numbered out of sequence. they go H1 H3 H2 H4 so I had them jumped wrong. lol...So when I switched them around then I got 22 volts DC on the black and red wires on the blue thingy with the fins on it. The other transformer with the buss bar on top of it I got 130 AC on the 2 wires on the far right. X1 and X2...The magnetize light now came on also. However still no magnetizing on the chuck. When I cranked the knob up to full power the light went out and I blew one of the fuses going to the Selectron, so now I'm dead in the water until I buy some more of the little $35 fuses.
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Does anyone know if the 2 wires going to the magnet from the controller should read voltage if checked ? I get 0. But if I put positive probe on either one of the wires going to chuck and the black probe of test to the negative of the rectifier I get 24 volts. so this seems to me that both wires going to the magnet are positive and neither one is negative. I really need a wiring schematic or wiring diagram for this control or some pics of one that works. I think there are some wires hooked up wrong.
eKretz
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If it's a 24VDC chuck there should be 24VDC across the wires going to the magnet. I'm going to copy this thread over to the electrical forum section also. Are there 3 wires in the plug that go to the chuck? There could be two separate coils, with both returning on the same 3rd wire for ground. I think I see a plug like that, is that what goes to the magnet? Not very clear from your photos.
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And sorry, didn't see this until you pinged me in the other thread. Then I forgot to look it up until just now. Moved the thread here to get a few more knowledgeable eyes on it.
Edit:
And sorry, didn't see this until you pinged me in the other thread. Then I forgot to look it up until just now. Moved the thread here to get a few more knowledgeable eyes on it.
thank you, and yes there are 3 wires on the plug but the middle prong is not connected to anything in the controller. In other words; its not used. just the 2 outside prongs are used and they both seem to be positive. I don't seem to have a negative.
also, I get 6.4 ohms across the 2 outside prongs going to the chuck.
and if I turn the dial up to full power it kicks the breaker in the controller. While not hooked to the chuck.
eKretz
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That works out for a ~90ish watt load @24VDC, and I recall your tag saying 100W, so that checks out as the two ends of a single coil wire. Do you have a voltage across the two receptacle connections that accept the plug when the controller is on? If not, something is wrong. Also have you checked the resistance from those plug prongs to the body of the chuck? That will give you an idea of whether you've got a short, just to be sure. It sounds to me like maybe you could have a wiring problem from when you changed the taps on the transformer(s).
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There is no voltage across the 2 prongs in the socket coming out of the controller when the controller is on. But if I put one probe on 1 prong and the other to the negative on the rectifier I get 24 volts. If I touch the probe to the other prong in the socket with the negative still touching on rectifier, I get 24 volts as well. So its as if both prongs in the socket coming out of the controller are 24 volts positive and no negative. I tested for continuity from both prongs in cord of chuck to the chuck and have no reading ; so coils don't appear to be shorted to chuck body. I put the taps on transformers back to original position and turned controller on. There was only 65 VAC off one of the transformers ( supposed to be 120 I think ). The magnetize light was very weak and the timer motor that activates damag cycle turned really slow. So I put them back the way I had them and got the 120 VAC back.
eKretz
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I think my first step would be to start tracing wires from that female receptacle and see where they go. Remove it and see if there's a wire connected to that center pin or not. I find it hard to believe that it would be there for no reason.
Without a schematic it's hard to diagnose stuff like this over the Internet. And I'm not so sure that the blue thing is a rectifier. The tube numbers show *those* to be rectifiers.
Without a schematic it's hard to diagnose stuff like this over the Internet. And I'm not so sure that the blue thing is a rectifier. The tube numbers show *those* to be rectifiers.
I believe it is a selenium rectifier.
I looked at the backside of the socket in the controller and the center prong doesn't have anything connected to it. I think the positive and negative DC is supposed to go out the 2 wires and that they flip during demag.
I looked at the backside of the socket in the controller and the center prong doesn't have anything connected to it. I think the positive and negative DC is supposed to go out the 2 wires and that they flip during demag.
eKretz
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Yeah, that's possible. Weird that they'd have multiple different types. You're probably right about the demag. I think you're down to either starting to trace some wires yourself and making sure none are in the wrong place or just rewiring completely with more modern kit. Maybe run 24VDC, 5A minimum power supply straight to the magnet and see if it holds well before investing the time.
Ok, do you have any ideas for the power supply ?
Do you know what the effect of the rheostat is in the controller? Does it turn up/down volts or amps to increase or decrease holding power ?
eKretz
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The rheostat looks like a Variac. It is varying AC voltage at the input of the rectifier, which raises or lowers the DC voltage at the output. The amperage is affected by this voltage change as I=V/R.
cyanidekid
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I have a Selectron, don't know the model number but its an older all tube unit, so probably can't help, but if anything looks similar, I can try.
P.S. include model of SG and year if known, that will help narrow it down. also, if you are getting a blown fuse with no output, (on a 100W supply no less) something is a short. its either mis-wired, or internally shorted. get the multi meter on it and chase that down.
P.S. include model of SG and year if known, that will help narrow it down. also, if you are getting a blown fuse with no output, (on a 100W supply no less) something is a short. its either mis-wired, or internally shorted. get the multi meter on it and chase that down.
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and when I turn it to full power it trips the breaker even while magnet is not hooked up
I have been thinking the same thing that something is shorting out. And I have probably 20 hours with the multi meter trying to find the short and chasing down the wiring trying to figure out what goes where. I also have a theory that both the mag and demag is on at the same time drawing too much power and tripping the breaker. Which also would explain why both the prongs in the socket going to magnet are positive and no negative. I am going to check out the mag/demag toggle switch next and see if it is sending power to both circuits.
Machine is a 1962 DoAll D10-30
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