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Post by Adam D. on Oct 21, 2013 21:28:11 GMT -5
What he's saying makes absolute sense to me.. Shorted windings means higher current to the rest and, anything shorted will cause the fan to run a bit hotter too.. I've had a fan that had a short in one of the windings and it didn't noticeably slow down and was drawing more current.. In fact it took a few damaged areas to where it noticeably was slower on low speed.. And that was with that CEC Emperor that I replaced the whole motor out of a Heirloom.. I found these Rectifiers at Radio Shack.. Something that Radio Shack actually has something worth buying, if all goes well.. www.radioshack.com/product/index.jsp?productId=2036270
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Post by Deleted on Oct 21, 2013 22:25:46 GMT -5
I dont know about the motor in your CEC, but K55 motors are impedance protected. That means, even stalled, it will never heat up past a certain point or draw a significant amount more current. The only way it can draw more current is if the motor is actually damaged. And if the motor is damage, you WILL notice a drop in performance.
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Post by Adam D. on Oct 21, 2013 23:04:40 GMT -5
Are you sure about that? I had a blender fan that got caught up in romex wire, back in the 1990s.. One whole week I noticed a smell coming from the garage (blades melting), and finally realized it. Needless to say, I could have cooked my whole breakfast using that motor.. It was a K55 motor.. When I removed the wire from being caught, the fan slowly started spinning..
That doesn't mean the motor gets hot enough to activate the thermal shut down if it even has one.. A short in one winding, depending on the winding, doesn't necessarily mean the performance of the fan is going to noticeable change, that's with ANY motor.. And anything shorted means MORE current throughout the rest.. Most of the time, it does no harm to the rest of the motor depending 'again, where the short is, the motor can run for 100 more years.. The windings can handle slightly more heat...
I'm done discussing this.. Say what you want..
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Post by Deleted on Oct 21, 2013 23:11:28 GMT -5
Blades melting?! What you probably smelled was the insulation baking. Did the fan run after that?
I've recovered some fans that were stalled for years, and when I unfroze the bearings, they still ran.
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Post by Adam D. on Oct 22, 2013 1:22:43 GMT -5
There was wet sticky gooew on the blades where they mount to the irons.. I didn't think fiberglass could melt so easy, unless it was insulation from the motor dripping.. And to this day I still remember the awful stench.. Surprisingly the fan did run after that.. Ya, it's amazing what motors can be put through and still run..
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Post by Deleted on Oct 22, 2013 7:44:29 GMT -5
What eventually happened to that fan?
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Post by Adam D. on Oct 22, 2013 15:35:58 GMT -5
I think it was one of the fans I left behind back in Sept of 2000 when we moved out of the house I grew up in.. I was to move out on my own and had a bunch of stuff that I had no place for.. Unfortunately I left behind a few neat Blenderfans, and alot of other neat stuff that I had even dating back to elementary school.
I replaced all rectifier diodes and even replaced the MOV chip and there is no difference.. The current 5k pot im testing with still gets hot, and fan speed at lowest setting could still go a tab bit slower.. The transistor is good and all resistors are within tolerance range, one other thing I may try is to replace the resistors, they may test good but it's possible when they are under current they may drift.. And if that doesn't do any good, than the only logical explanation is a shorted winding = more current going into the board, and have to move up a bit on the k'ohms and wattage with the control to confinsate.. Or replace the motor..
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Post by Deleted on Oct 22, 2013 15:50:52 GMT -5
My point was that stalling out didnt damage the motor, it didnt get hot enough to hurt the windings.
I'm telling you nothing is shorted . . . if you want to know for sure, get an amp meter, and measure.
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Post by Adam D. on Oct 22, 2013 16:23:20 GMT -5
Ya, but. There is defiantly some logical reason why this is happening.. If I replace everything on the board with the right components and working as should and the fan is still burning pots out and not as slow as should be, then the problem is simply elsewhere..
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Post by Deleted on Oct 22, 2013 16:42:07 GMT -5
Except that the design on the board is simply a bad design.
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Post by John Shelley on Oct 22, 2013 17:10:30 GMT -5
how about a bad running cap or the insulation between the transistor and heat sink starting to break down?
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Post by Adam D. on Oct 22, 2013 17:53:29 GMT -5
The insulation between the heatsink and transistor looks like it's in great shape, the piece of rubbery material has no cracks or anything that looks out of the ordinary.. I've touched the heatsink after the fan has been running for a while, and it gets warm. I could try another cap also.. What would you recommend? I've done a search of that value and nothing much comes up of the that type of cap..
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Post by John Shelley on Oct 22, 2013 21:35:45 GMT -5
you could try a 10 uf oil filled cap in the motor housing in place of it, hooked to the same 2 wires that the one on the board would have gone to, which should be the red and brown ones. I have multi meter that can test caps, its a must if you work on motors alot (or a separate capacitor testor) since they can go out of spec without looking bad, if you dont have one its much harder to test them other than try a known good one. can make sure that you have no continunity between the transistor and its heat sink, I wound if it was mine hope that there is at least 1megaohm resistance between them, even better would be out of range, they have insulation been the screws and heat sink that can go bad also, I used nylon bolts to attach the replacement transistor when i rebuilt mine
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Post by Deleted on Oct 22, 2013 22:02:13 GMT -5
If the cap was bad, 9 times out of 10 it drifts lower, not higher, and the fan would run slower. Easy to test the cap, you can get a cap tester for $12 shipped on eBay.
For it to drift high enough enough that the motor would draw enough current to fry the circuit, pretty soon the motor would overheat in other ways.
Checking the insulation is a great idea.
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Post by Adam D. on Oct 22, 2013 22:11:17 GMT -5
I have an ohm meter that can test caps, but can't test it while in operation.. I've seen testers that are specifically made for caps and it test leakage, everything, etc.. The insulation that covers the wires you mean, that go through that heatsink? those are appear to be fine too...
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