I am getting low output DC power in the treadmill PCB

Thread Starter

manishvatchas

Joined Jul 18, 2022
6
I am getting an issue with my treadmill PCB board. there is no led blinking. When I give 250V at the input end. I am getting 84V DC at the output end and the required power is 180Volt DC. My treadmill controller not getting power from PCB. what I have checked I am mentioning below.

1) I have checked the input supply at the PCB board. that is coming AC 250V. my EMI MC Filter and coil transformer are ok voltage is passing across them.
2) I have given direct supply to PCB input what I got at the output is 84V DC maximum. what I noticed, is that the reading first starts from 48V DC then gradually increases, and after 2-3 minutes it reaches 84-85 V DC maximum. Then motor rating is 180V DC. I think at output voltage is required to be 180V but in my case is 100V less.
3) I have checked the big capacitor 470UF 400V. they are charging up to 500UF.
4) checked the main board bridge rectifier I checked in live the voltage I getting from the bridge rectifier is 500-510V DC.
5) I also replace the IGBT and Schottky diode from the PCB board. by watching online. but before and after results are the same which means old IGBT and Schottky diode are also good.
Please help me this treadmill is the memory of my uncle. who passed away last year due to covid.
 

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MisterBill2

Joined Jan 23, 2018
12,696
To do a smart fault tracing effort you will need to have enough information to be able to follow the power through the circuit. This means that either you will need to trace the circuit board conductors or get a circuit schematic .
AND I wonder if those voltages measured are with any load applied or not. Otherwise you will be stuck doing random component checks until you find some failed part that may or not be the source of the problem. I do not recommend that method.
Have you checked the voltage at the driver transistor terminals. And, one other question is what are you using for the negative side of your voltage measurements? That connection has just as much effect on the reading as the positive side connection.
One question is about the motor itself. Does it turn freely? A failed motor can overload a driver circuit. Have you checked the fuses hidden on the circuit board.
Have you inspected for failed connections in the wiring? These are all possible causes.
 

Thread Starter

manishvatchas

Joined Jul 18, 2022
6
To do a smart fault tracing effort you will need to have enough information to be able to follow the power through the circuit. This means that either you will need to trace the circuit board conductors or get a circuit schematic .
AND I wonder if those voltages measured are with any load applied or not. Otherwise you will be stuck doing random component checks until you find some failed part that may or not be the source of the problem. I do not recommend that method.
Have you checked the voltage at the driver transistor terminals. And, one other question is what are you using for the negative side of your voltage measurements? That connection has just as much effect on the reading as the positive side connection.
One question is about the motor itself. Does it turn freely? A failed motor can overload a driver circuit. Have you checked the fuses hidden on the circuit board.
Have you inspected for failed connections in the wiring? These are all possible causes.
Sir, i am a Mechanical guy. i have checked the blub fuses they are ok. But i have found any other third hidden fuse. Can you please mentioned on the image please. Regarding motor i have checked motor is rotating freely.

Can you please mentioned which transistor you are taking. Also which portion of the pcb my problem lies.

I will be great if you please mark on my pcb image. All the components and checks you are talking that I have not checked yet.
 

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Thread Starter

manishvatchas

Joined Jul 18, 2022
6
Have you checke4d the device that senses belt speed,? it can be either on the end of the motor or a proximity type on the belt.
i don't think speed sensor has any role with the power. but i have checked before the fault it was working properly. i am waiting for some positive hope.
 

MisterBill2

Joined Jan 23, 2018
12,696
The "transistor I mentioned would be the one that you replaced.
I am guessing that the motor is the kind with brushes and a commutator, and not the brushless variety. Diagnostics for the two kinds are rather different.
My service technique is usually to look at the circuit schematic drawing and understand how it should function, and compare that with what is happening, and then take some measurements to verify where the problem is located. Inspection is good for finding broken parts and physical damage, but seldom reveals the cause of the problem. And usually the burned up part was the victim of the failure, not the cause of the failure.
 

MaxHeadRoom

Joined Jul 18, 2013
25,630
My service technique is usually to look at the circuit schematic drawing and understand how it should function, and compare that with what is happening, and then take some measurements to verify where the problem is located
You rarely get that luxury with proprietary equipment like T.M.'s. unless someone has reverse-engineered it as has been done with the popular MC60/MC2100 models.
 

MisterBill2

Joined Jan 23, 2018
12,696
Others have located circuit information if the posts at this site are believed.
What better diagnostic scheme do YOU suggest? Most parts that fail do not display much change, and usually the part that burns up is the victim, not the culprit. And randomly testing components is slow and not efficient.
 

MisterBill2

Joined Jan 23, 2018
12,696
It may also be possible to trace the wider runners acoss the circuit board. The point being that some point in that loop there must be an excessive resistance.
 
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