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| Einhell MTB3000 minilathe potentiometer |
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| cre8tor:
Hi! First, thank you for letting me join in MadModders forum! I bought 10 years old fairly used Einhell mini lathe. For first start nothing happens, I rotated motor by hand and it scratches. I took off it and cleaned, now it works fine. Next problem is (maybe only pot) on control panel. Potentiometer says B4.7K, so I think its linear 4.7KOhm pot with on/off switch. When I turn little bit clockwise potentiometer, it cliks and lathe turns on (when all other switches has turned on), but I can't adjust lathe motor speed on potentiometer. Is this potentiometer problem or something else in circuit board? I find it to be hard to find exactly same pot on internet, but one I ordered from ebay, I don't know if it fits? http://www.ebay.com/itm/161675373526?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT Please give me any help with this lathe electronics, thank you! |
| John Rudd:
Hi and welcome to the forum...... :wave: If the speed pot has no effect on the motor then in all likelihood the problem is the control board..... If you disconnect the motor from the wiring, connect a 100 watt lamp bulb in its place, does the speed pot vary the brightness of the bulb?( make sure the bulb voltage is the same as your line voltage....) Can you post up,some photos? Control board?....pot? Lathe? Where about in the world are you? |
| cre8tor:
I ordered potentiometer today and haven't got it yet for testing. I am from Finland. So do I try 100W 230v AC light bulb on motor wires? I really don't know if there is rectifier and motor works DC supplied voltage? Or is these all voltages AC? I took some pictures of lathe, pot and circuit board: |
| John Rudd:
Ok, The board is made by KB electronics in the USA, generally reliable but they do blow thyristors...(scr)....Do you have a multimeter? The motor is a dc motor, so do not connect it to an AC supply...!! :zap: The dc for the motor comes from the pcb, there is a Full Wave bridge rectifier made up from 2 thyristors and 2 diodes, mounted on the heat sink....Don't work on the board Live.....!! :zap: risk of electric shock.. :lol: The potentiometer may be a 'special'.....but for now concentrate on getting the motor controlled by the controller..... Disconnect the motor wires, make a note of where they go! Then connect a 100w bulb in its place.....does the brightness vary as you adjust the speed pot? If not then you need a multimeter to diagnose further..... |
| cre8tor:
Ok. My thought of that motor is DC were right :) I have Fluke multimeter ofcourse, why I have to use light bulb to check voltage? I can measure voltage with multimeter. Have to try that. If SCRs are bad, are those hard to get? I give that circuit board and motor to my friend, who are guru of electronics. He can find the problem :) |
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