Hi All

Really hoping I can back into my electronic repair hobby with some help. I had a treadmill “run-away” speed went full and a MOSFET blew. I replaced IRFP250N properly with the insulating/thermal pad. Now the motor works but it has no strength, no torque - as if it’s not getting enough current.

This seems to be common issue from browsing the threads - any help appreciated.

Martin

 

Never come across that version, but check the DC once it ramps up.

 

The actual board though is the same as one i’ve seen around these threads. With the reverse engineered schematic - I confirmed the PWM signal and speed sensor. I have a burn mark on heat sink next to the high power white resistor - although it is reading correct value (3.3k I believe).

I’ve seen a lot of threads with the same issue. After replacing the FET - the motor works, but has no “strength” to it. I could stop it with my hand on the belt. The DC power is ramping up - although on the oscilloscope - the power looks dirty, not a clean power signal - if i look at 10us timing.

 

Is the current sense (0.01Ω) resistor OK?

 

Is the current sense (0.01Ω) resistor OK?

let me check it - can you remind me which one that is ?

 

R32..

let me check it later & and thanks for your help so far.

 

The black resistor looks good, very low resistance measured.

 

Have you tried the motor on a separate supply?
It should have quite a bit of torque, even on a 12v automotive battery. Check current at the same time with the test and some load applied.

 

I can try on a high amp 5V supply - is that sufficient to test motor’s torque ?

 

Higher the V the better .

 

Higher the V the better .

Hi - so I attached an old xbox PSU (12v - 16amp)
Motors spins at constant speed, but has same low torque issue. I could stop motor with my hand - I suppose at this point it seems the motor is bad ?

Up to this point I’ve replaced all the components on the heatsink. Motor is measuring ~ 1ohm across it.

Thanks