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Aug 20, 2011 16:11:07 GMT
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The capacitor will be, as mentioned above, either required for the motor to run, or simply to start. AC motors are very strange items.
Wiring will normally go:
live wire > switch > capacitor > the main cage (I can't for the life of me recall it's name atm...) > brush > stator > brush, then either straight back the switch, or (on the better ones) back through another set of windings on the outer cage thingie
No need to plug it in, use a multimeter on the resistance setting - but obviously you can't check the capacitor, as it'll just act like an open circuit. You should get a resistance of around 100 Ohms. Don't forget to turn the motor to check it's not sporadically cutting out/shorting out (resistance will obviously either go very high, or drop a small amount.
Checking the switch with a multimeter takes 5 seconds....
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You're like a crazy backyard genius!
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Aug 20, 2011 18:25:43 GMT
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the main cage (I can't for the life of me recall it's name atm...) Armature!
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Aug 20, 2011 19:16:28 GMT
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lol, not the middle bit - the outer, non-moving bit!
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You're like a crazy backyard genius!
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Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,784
Club RR Member Number: 34
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Aug 20, 2011 19:19:10 GMT
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id also expect it to be brushes.
but £80 for a grinder? someone got mugged.....
ive just replaced my makita today. 5 years solid service, minimum 2-3hrs a day of professional metalwork fabrication. still on the original brushes(!), switch and plug- ive replaced the cold once, my own fault for dropping a sheet of steel on it edge on. finally died due to a crunched/stripped bevel gear pinion. it cost about £40+vat back when i bought it, so less than £10/year. what did i replace it with? exactly the same model, still the same price. there is no better angle grinder!
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bxer
Part of things
Posts: 457
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Aug 20, 2011 20:27:09 GMT
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lol, not the middle bit - the outer, non-moving bit! stator
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Aug 20, 2011 21:59:57 GMT
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Sorry if I sound like a grumpy g!t but there's a lot wrong with this thread!! Fixing anything involves two stages: find the fault...then fix the fault. So far, as far as I can see we still don't actually *know* what the fault is. Sure you can use 'replacement' as a legitmate fault finding technique, but it gets expensive when you have to buy the replacement parts! In general terms to fault find, you split the system in half and check that all the 'conditions' are correct at that point. Depending on the result, you then work forwards or backwards. In the case of the grinder I'd check on the output side of the switch. If you know what you're doing you can check with it live and plugged into the mains I measuing AC volts. But if in *any* doubt at all, do it without being plugged in and use the continuity check. If you've got continuity up to the switch (on both live and netural sides) you know the fault is in the motor area somewhere - windings, brushes, capicator. If you don't have continuity then it will be the switch, lead plug (if it has one) or mains lead. Ermmm... I did already check the switch. That works but have some serious doubts about the capicator. The capicator comes with the switch so both bits will be replaced. At least that won't cost much. id also expect it to be brushes. but £80 for a grinder? someone got mugged..... ive just replaced my makita today. 5 years solid service, minimum 2-3hrs a day of professional metalwork fabrication. still on the original brushes(!), switch and plug- ive replaced the cold once, my own fault for dropping a sheet of steel on it edge on. finally died due to a crunched/stripped bevel gear pinion. it cost about £40+vat back when I bought it, so less than £10/year. what did I replace it with? exactly the same model, still the same price. there is no better angle grinder! Can't say I've used mine quite as much. The brushes look half-worn at this stage. I have had it about 5 years. The previous one came from homebase and cost around £15.00 - rough and ready but worked and lasted for ages until the brushes went. You could say paying £40.00 when you can get a durable one for £15.00 is foolish. The Homebase one was a 'PowerDevil' if I remember rightly. There's the little curse word.
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Aug 20, 2011 22:30:25 GMT
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Wrong end of the stick there chaps, of course you should fix it, but I have occasionally found that once that path is exhausted and i've resorted to buying a new one the old device - often once tested again some time later - mysteriously works as it did before. Ah! Sort of the "buy-new-parts-and-you'll-find-the-missplaced-ones" strategy ;D That's a very strong voodoo and almost always works ;D
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id also expect it to be brushes. but £80 for a grinder? someone got mugged..... ive just replaced my makita today. 5 years solid service, minimum 2-3hrs a day of professional metalwork fabrication. still on the original brushes(!), switch and plug- ive replaced the cold once, my own fault for dropping a sheet of steel on it edge on. finally died due to a crunched/stripped bevel gear pinion. it cost about £40+vat back when I bought it, so less than £10/year. what did I replace it with? exactly the same model, still the same price. there is no better angle grinder! DeWalt angle grinders were on sale at B&Q last year for under £40 - I think it was something like £37.99. I was tempted for a few seconds and then realised I'm more than happy with my Makita and various £9.99 supermarket specials Paul H
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Aug 21, 2011 15:54:38 GMT
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Pull the brushes out and check them for the clever spring thingy previously mentioned. It stops you where there's "loads" of brush still left on the Makitas. (I use the 125 quid 1400W vari speed 4.5" jobbies for cup brushes and grinding, and the 25 quid 700W single speed 4.5" jobbies for cutting/flapdiscs) Ceramic dust kills them faster than anything else IME.
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-- Marko
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Aug 24, 2011 11:26:43 GMT
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Some clever so and so's on this forum ain't there! ;D
After changing the switch the grinder still does not work and I checked the brushes and found they do have that silly little spring in them and it is showing through on one side. Never mind switch was only 4 squid. More annoying is that I'll have to wait for the brushes now. Still well up on the deal though. £80.00 for a new grinder or £8 on spare parts... no brainer really.
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Aug 24, 2011 11:50:15 GMT
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Hope it works dude
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You're like a crazy backyard genius!
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Aug 24, 2011 22:21:59 GMT
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just pull the springs out with some pliers and replace later on, mine have done another year since i removed them :-)
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