So i ended up with an old junk treadmill figured be fun to tinker with, part out or maybe try and use. The main board had issue with the elevation motor i found an electrolytic cap had failed swapped that it went all the way up then down then back up slightly which it did not do before. I was told that incline was just stuck at like 2.X. Also told it did run but after some time it would trip the internal breaker. I figured maybe weak breaker, but still not sure they seemed to think maybe needed oil and load on motor was issue. However i can't even get it the tread to spin. I set in in a running mode, looked at the LED the power/logic board had MWM LED pulsing and so did this MC-60. MC 60 also had 12V LED on, but SCR trig was totally dead. Current limit LED was off too.
I used a DIMM and checked for open resistors, diodes, etc all looks ok. I traced around the PWM LED thinking that is probably tapped off whatever drives the SCRs. I see an opto isolator, some resistors, etc. one lead off of an ST LM324m to that part of the circuit. The schematic sheet inside the thing just says replace the MC60, but i don't really have much interest spending much on this as main board could still have issues, motor could be near toast, etc.
I did notice though that something marked RPS and looks like resistor 42 is missing. I see no burn marks on the PCB but thought maybe that failed and fell off. But seeing some other pics this seems to be cut off too. From the schematics i have seen that is part of the current limit circuit. I initially thought maybe if that skews it too much even no load motor being connected would be overcurrent but now that i think about then the overcurrent LED should be on. Short of testing the optoisolator or the ICs on this i don't see what issue would be.
I am also finding it odd that this has ICs at all as the PWM is feed into this from the console PCB which then passes through the power PCB and to this one. And to me the H and L terminal look like maybe logic power from the other PCB and the W is the PWM signaling. I see a trimpot with some rust on top of it but continuity it seemed fine. I see no sign of any other issue like other blown caps corrosion, burned, electrical smell, etc.
I have many DIMMS, i have a fluke scope although i do not know a ton about using it yet. I have stash of old caps, resistors, etc so probably have something i can put in if needed. I am just kind of lost at this point short of desoldering parts and testing open circuit, etc which if it is going to be that bad i would just assume part the thing out. Just seems to me there should be some simple piece that goes between the PWM input coming in and the SCR trigger, i honestly thought it would just go right to an SCR, but it appears there is more to this thing.
I guess wondering if there are any ideas where i should look, things i could probe, i also saw something about this board could be controlled by a potentiometer would that or something else be any good to test this. The PWM LED lights on it so I assume that input is working so thinking issue lies in the middle somewhere?
I used a DIMM and checked for open resistors, diodes, etc all looks ok. I traced around the PWM LED thinking that is probably tapped off whatever drives the SCRs. I see an opto isolator, some resistors, etc. one lead off of an ST LM324m to that part of the circuit. The schematic sheet inside the thing just says replace the MC60, but i don't really have much interest spending much on this as main board could still have issues, motor could be near toast, etc.
I did notice though that something marked RPS and looks like resistor 42 is missing. I see no burn marks on the PCB but thought maybe that failed and fell off. But seeing some other pics this seems to be cut off too. From the schematics i have seen that is part of the current limit circuit. I initially thought maybe if that skews it too much even no load motor being connected would be overcurrent but now that i think about then the overcurrent LED should be on. Short of testing the optoisolator or the ICs on this i don't see what issue would be.
I am also finding it odd that this has ICs at all as the PWM is feed into this from the console PCB which then passes through the power PCB and to this one. And to me the H and L terminal look like maybe logic power from the other PCB and the W is the PWM signaling. I see a trimpot with some rust on top of it but continuity it seemed fine. I see no sign of any other issue like other blown caps corrosion, burned, electrical smell, etc.
I have many DIMMS, i have a fluke scope although i do not know a ton about using it yet. I have stash of old caps, resistors, etc so probably have something i can put in if needed. I am just kind of lost at this point short of desoldering parts and testing open circuit, etc which if it is going to be that bad i would just assume part the thing out. Just seems to me there should be some simple piece that goes between the PWM input coming in and the SCR trigger, i honestly thought it would just go right to an SCR, but it appears there is more to this thing.
I guess wondering if there are any ideas where i should look, things i could probe, i also saw something about this board could be controlled by a potentiometer would that or something else be any good to test this. The PWM LED lights on it so I assume that input is working so thinking issue lies in the middle somewhere?