MC2100 Rev B - Treadmill Runs for a couple second then stops

Thread Starter

eewill

Joined Jul 27, 2020
18
Keeping up with progress, in case this helps someone else...
I really wanted to get the circuit function down before I just started testing randomly.

I tested the TACH reed switch. It works fine. I can even move the belt and watch the numbers change on the console.

I also completely removed the motor from the system and used a light bulb in it's place. I bypassed the motor's thermal switch as well. The light bulb only lit briefly before going out. So, the problem is on the board and not the motor itself.

Then I followed the path I outlined in a previous post.

It looks like the MOSFET is gone. It's tests shorted no matter which pins or direction I use.

I removed the MOSFET and tried to test the board in system again. I'm guessing that either something else is out, or another safety feature is shutting things down. I am not reading any voltage change on pin #8 of the micro or the gate node where the FET was. It stays at a constant 0.15V regardless of the speed setting.

I have a new MOSFET on order. Will have to wait and see what happens.
 

Thread Starter

eewill

Joined Jul 27, 2020
18
I have a better meter put away somewhere. I'll locate it and test it. I've got some time to continue testing while waiting on the MOSFET to come in.
 

Thread Starter

eewill

Joined Jul 27, 2020
18
What about the U5 driver? Is there an easy way to test it? I only have my meter.

Eventually, I'll get the MOSFET in and I can put it in the board and that will tell me something.... just trying to get ahead of things.
 

Thread Starter

eewill

Joined Jul 27, 2020
18
Looks like the MOSFET was the problem. I also lubricated the deck under the belt. After it started running, it would slow down when you stepped on the belt. It still does a little at very low speeds of 1 mph and under.
 

ymg200

Joined Oct 2, 2015
41
eewill, thank you for posting your troubleshooting experience!
My treadmill had same symptoms - starting fast (even lights in the house would blink), then shutting down after 1 second by the thermal switch at the motor. After I bypassed the thermal switch, the motor would run for 2 seconds, then the circuit breaker in the power switch would turn the treadmill off. High power to the motor was definitely the problem.
I found that the MOSFET had all legs shorted, just like in your controller.
I ordered new MOSFET from Ebay and replaced it. I ordered IRFP260 instead of the original IRFP250. IRFP260 has similar specs as IRFP250, but it has higher amperage and therefore less change to burn again.
My fix, however, resulted in a big failure. The treadmill has started nice and smooth after I've replaced the MOSFET, but after 3 seconds sparks were flying from the controller......
The controller is now in the worse shape than it was before my "fix", which makes me upset. The status LED doesn't light up.
I have attached the closeup of the area where sparks were coming from. R29 and R30 are burnt. C18 is charred, but I can't say if it is damaged too. My concern is MIC4427 (U5 in the circuit diagram), which is connected to burned resistors. How can I test if U5 has survived? The MOSFET now has a short between Gate and Drain - this what must have burned resisrors. As I said, the controller worked fine for few seconds after I've replaced the MOSFET, then the failure happened. Is it possible that I have compromised the MOSFET by overheating it when soldering?
I will replace burned resistors and the MOSFET (again), will see the status LED lights up.
Thy the controller was fine (apart from starting with max speed) when all three legs of the MOSFET were shorted, but the short between Gate and Drain have resulted in the critical failure?
How can I test if U5 is good? Any advice what direction I should take?
Thank you.
 

Attachments

MaxHeadRoom

Joined Jul 18, 2013
23,908
If the status LED does not light, check to see if you have 5v on the micro, pins 10 & 20.
If you do not check the 3.3k 7w resistor. & the 7805 RG1.
Max.
 

ymg200

Joined Oct 2, 2015
41
Max,
I've removed the MOSFET Q2 and burned components (R29, R30, C18) from the board, but I noticed 33Ohm between pins 3 and 6 of MIC4427 (U5). Pins 3 and 6 of MIC4427 are Gnd and Vs. 33 Ohm between Gnd and Vs doesn't sound right. I thought that maybe C17 is shot since it is connected to pins 3 and 6 and removed it, but C17 turned out to be fine and I still have 33 Ohm between pins 3 and 6 of U5. Does this mean that this chip is gone?
Thank you.
 

ymg200

Joined Oct 2, 2015
41
Sounds like it could be with those readings.
Is the Micro supply OK?
Max.
There is no voltage btw pins 10 and 20 of the micro. The 3.3K 7W resistor drops 107V, so the board is getting powered. There is a 1V drop btw pins 1 and 3 of RG1 (7805). However, since pins 3 and 6 of MIC4427 (U5) have low resistance btw them (30 Ohms), I feel that pin6 that is +5V is getting pulled to the ground that is pin3. Is that right?
I've removed the MOSFET Q2 and fried components (R29, R30, C18), but not the U5. See the attached picture. Should I remove the U5 and check the voltage again?
 

Attachments

MaxHeadRoom

Joined Jul 18, 2013
23,908
Sounds like the 5v is missing due to the 7805?
You should have 10vdc or 15vdc across the zener D8, whichever voltage is fitted.
This is the input for the 7805.
Max.
 

Mars67

Joined Feb 21, 2021
5
Good Morning fellow forumites. My apologies for chiming in here but I have a similar problem with a Nordictrack treadmill using a MC2100ELS 18v controller. Initially the treadmill would turn on when powered but would shut down when you press start. The motor would start turning for an instant before shutting down. It would then be completely dead (ie no flickering led indicating a fault code) but would turn on again when you reset it. I did some troubleshooting after researching this forum and found that the reed switch(hall sender?) on the belt drive pulley was not giving a signal. I repositioned it closer to the pulley and managed to get a signal. The belt was replaced by approved technicians some time ago and I suppose they knocked it.

The treadmill is still doing the same thing but at least now I am getting 4 led flashes when the treadmill stops. The motor will start turning momentarily before stopping with the four flashes. One can then press stop and the flashes stop.

I checked the motor with a bench power supply and it runs smoothly.
I checked all the resistors and diodes on the board and all are within spec. I see no obvious damage or indications of overheating and no swollen caps. I tried searching for error codes but the descriptions I could find are somewhat sketchy. I suppose I should remove the K50DDTP IGBT and JCT825a SCR and test them?
Any other suggestions would be most welcome. Thank you.
 
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