Hey guys, first time caller long time listener. Thanks for all the help with schematics and advice about this MC60 controller in the past. I had this current one working just fine a week ago and I really stupidly, and unknowingly, dropped a washer on/around R55 thru R37 area. Plugged it in to test my pulley system and SPARK!! Yes, I'm that stupid...
Now I get 12+, SPD CNTL, and SCR TRIG on solid with power, yet no motor movement with speed adjustment. Actually the SCR TRIG stays solid it just gets very dim when I adjust the speed. The CUR LIM light is also very, very dim.
I have already unmounted and tested all resistors in the area, only one had gone bad and have replaced. The IC at U1 was very suspect with a small black spot on the GND leg, so I just replaced it for a couple bucks to no avail. I then proceeded to test Q2 and Q3 with 9vdc and a fan. Both ran with short to gate and closed without so they're fine. D1, D2, D12... all good. Yet still no movement from the motor.
Finally I got some movement out of the motor when I took some advice and shorted the "SCR TRIG" LED with a piece of wire. As soon as I plugged the board in, the motor jumped into action at full speed. No adjustment of the POT made a difference. So I suspected the LED going bad. I removed the SPD CNTL LED and put it into the SCR TRIG spot and shorted the SPD CNTL LED out. Then I got nothing again? So I'm pretty sure the LED isn't the main issue.
So now no matter what I try the only way I can get the motor to run is by shorting the SCR TRIG LED... and it'll only run at full speed.
I tried to test the optoisolator LED, and it seemed to be fine. I'm not an expert though so I couldn't say positively. Should this be the next replacement or should I be looking more closely at the speed control POT?
Thanks for any advice.
Now I get 12+, SPD CNTL, and SCR TRIG on solid with power, yet no motor movement with speed adjustment. Actually the SCR TRIG stays solid it just gets very dim when I adjust the speed. The CUR LIM light is also very, very dim.
I have already unmounted and tested all resistors in the area, only one had gone bad and have replaced. The IC at U1 was very suspect with a small black spot on the GND leg, so I just replaced it for a couple bucks to no avail. I then proceeded to test Q2 and Q3 with 9vdc and a fan. Both ran with short to gate and closed without so they're fine. D1, D2, D12... all good. Yet still no movement from the motor.
Finally I got some movement out of the motor when I took some advice and shorted the "SCR TRIG" LED with a piece of wire. As soon as I plugged the board in, the motor jumped into action at full speed. No adjustment of the POT made a difference. So I suspected the LED going bad. I removed the SPD CNTL LED and put it into the SCR TRIG spot and shorted the SPD CNTL LED out. Then I got nothing again? So I'm pretty sure the LED isn't the main issue.
So now no matter what I try the only way I can get the motor to run is by shorting the SCR TRIG LED... and it'll only run at full speed.
I tried to test the optoisolator LED, and it seemed to be fine. I'm not an expert though so I couldn't say positively. Should this be the next replacement or should I be looking more closely at the speed control POT?
Thanks for any advice.