My post is lost again! I wrote the answer to you and now I see it is missing
asdf53 wrote on 2025-10-27, 14:37:First test, not 100% sure if it works but try it: Put multimeter in diode mode. With battery connected and the switch off, test from controller pin 12 to battery negative. Repeat with the switch on. In theory, this will allow you to test if pin 12 is actively pulled low (low reading) or not (high reading).
Same with switch On/Off, meter beeps and shows 0.17 on it (not sure what)
asdf53 wrote on 2025-10-27, 14:37:Next, measure the current:
With the battery disconnected, write down which microcontroller pins are connected to the positive battery terminal. If pins 9 and 10 are not among them, find out where they go as well.
None of the pins are connected, but here is the strange part. Pin9 & Pin10 beeps for a moment and then it doesn't anymore. But this is only if I connect the battery and then remove it. Is it possible that some charge was left after battery removal?
asdf53 wrote on 2025-10-27, 14:37:With battery connected, on one of the controller's supply voltage pins, measure the voltage. Turn the switch on, measure again. The measured voltage difference will allow you to calculate the approximate current, but if the current is too small and your meter is not sensitive enough, this will not work. Then you need to measure current directly with the multimeter in ammeter mode:
Here are the voltages with switch Off/On:
Pin1 is 4.03V and it drops to 0.06V
Pin3 is 1.99V ant stays the same 1.99V
Pin8 is 4.06V and it drops to 3.89V
Pin9: when I connected probe to it the motor started to spin and it didn't stop until I removed the battery 😳
Or maybe I did something else as this happen to me already last night, while I was checking the pins on micro controller
asdf53 wrote on 2025-10-27, 14:37:Board positive connector > battery positive
Board negative connector > multimeter positive lead > multimeter negative lead > battery negative
Not sure that I get this part? Isn't battery positive terminal and board positive terminal same thing?
asdf53 wrote on 2025-10-27, 14:37:Another thing you should test is the large electrolytic capacitor. If it's dead, then the large initial current draw of the motor can cause the voltage at the microcontroller to sag, causing it to reset and getting stuck in an infinite loop. This would be consistent with the lower supply voltage you measure after turning the switch on. You could test this theory by holding a second capacitor on the battery connector pins while turning the switch on.
Does it need to be the same? 25V and 100 uF
boby wrote on Yesterday, 13:37:Does it need to be the same? 25V and 100 uF
No, just a capacitor of any voltage with 100 uF or more. The more the better, try 1000 uF. Hold the capacitor onto the battery connector pins with the correct polarity, then turn the switch on. Does it start?
Same with switch On/Off, meter beeps and shows 0.17 on it (not sure what)
Since the diode reading is low, it means that pin 12 is actively pulled low. This could either mean short circuit or the controller simply doesn't react to the button press. It's very interesting that you were able to turn on the motor by accident - this means that the controller switched pin 12 to 4V, there is no short circuit in the controller, and the basic switching mechanism is intact.
None of the pins are connected, but here is the strange part. Pin9 & Pin10 beeps for a moment and then it doesn't anymore. But this is only if I connect the battery and then remove it. Is it possible that some charge was left after battery removal?
If none of the pins are directly connected to the battery, then the controller is probably powered by one of the three transistors above it. Test if there's a connection. Short beep and then stop could mean the transistors were still open from the battery power and then closed.