Thanks.If the voltages are the same without the motor connected (this may be an expected condition) then measure them with the motor connected.
If the voltages are the same with the motor connected then probably the triac/thyristor (three legged black thing) is short circuit. It may be other things but that's the first thing to check.
which component pin ?In Z2.jpg picture I see a component pin coming thru board that does not look soldered properly.
The triac works like a switch. It is now (maybe) short circuit - the switch is permanently on.if problem is for damaged triac, would you please tell me what happend when the triac is damaged and why input and output voltages are the same.
i disconnect the triac and connect it to digital multimeter.The triac works like a switch. It is now (maybe) short circuit - the switch is permanently on.
Do you have a meter, can you disconnect it from the mains and measure the resistance between the legs of the triac?
I measured the values by multimeter.That's a pretty basic test but it looks like the triac is OK.
Next you could check the values of the resistors on the board including the variable one.
Also if your meter has a capacitance range, check the little brown capacitor value.
The joints with red arrows look suspicious and the track with yellow arrow possibly has a crack but it might just be a scratch on the solder resist.I checked the soldered joints with magnifying glass. also i test them with multimeter but no fault found.
attachment is a board picture with high quality.
It was tested. Results in the attachment to post #8.Given the things that you have already checked and found to be OK, the item left is the variable control resistor. Checking that it varies the resistance as it is turned is the one thing that I did not see suggested.
The values of that variable resistor are not reasonable. Normally a variable resistor should be able to be set to a quite low value of resistance, but I think that the complaint is that the thing runs at full speed no matter what. Are you using it with the original motor that it was controlling?It was tested. Results in the attachment to post #8.
would you please draw a correct circuitI studied my reference materials and conclude that there is an error in the drawing on post #8. One or the other of the resistors should be connected to the gate side of the diac, instead of both resistors being in parallel. AND, if there really is no pull-down resistor connected to the gate, that may be why the control is full on all of the time. In addition, the values of the two resistors seem to be quite high, more than would be expected.
One more possibility is that the switch to operate the grinder has three positions, OFF, variable speed, and full speed with bypass. And if the connection is not right then the only speed is full speed. So if the trigger switch has three terminals that might be the source of the problem.
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by Luke James
by Luke James
by Robert Keim