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| Einhell MTB3000 minilathe potentiometer |
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| John Rudd:
It's not a case of measuring the voltage at the motor connections.....you need to see the effect....hence the variation in brightness of the bulb... The out It from the control board to the motor is not pwm signal more like 'burst fire control'.....the thyristors are switched on at various angles of their conduction from a zero crossing point detector....without getting too technical..... The spare thyristors are or can be expensive to source....Are any if the fuses blown? If not then they may be ok....check with diode test function on you Fluke between Anode/Cathode and Gate.... |
| cre8tor:
Ok, I got it. No fuses blown and motor runs but on very low speed and potentiometer won't speed it up. I found those SCRs from aliexpress, price was 15€/pcs, not too much, but if they are ok, I don't even need those. I hope that pot is the problem. |
| John Rudd:
Ok, A few things to check..... Check for 12v between I2 and the outer legs of R1 (max speed pot....one end goes to the 12v rail, the other goes to P3. If that checks out, check the voltage varies, connect Fluke to I2 and P2..... Does this voltage vary when the speed pot is varied? Don't forget mains is present, keep your hands clear when measuring(use croc clips....) |
| cre8tor:
I have measured points you said, between I2 and 12V Rail were 12V. And between I2 and P2 voltage varies between zero to 7V. |
| John Rudd:
Hmmm...to go much further needs more test equipment...... Oscilloscope, low voltage transformer (around 40v ac).......to start.... You need the transformer to operate the board at a lower voltage that is isolated from the mains, the scope to check the waveforms..... |
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