need help treadmill motor controller short

Thread Starter

tigerlineman

Joined Nov 27, 2015
14
Subject: Life master T9i

Hi I have been trying to repair my life master T9i treadmill. I believe an electrical storm shorted the controller board. I had a service rep come to my home and couldn't fix it. I replaced the bridge rectifier and the 4 IGBT's (2 two prong and 2 three prong). I now get power to the board and the 6 LEDs light, the console says low level voltage error. I have the motor wires off. When I connect the thermal cutoff wires from the motor ( both blue), I short it out. (I have a short bulb socket attached to a 1500 watt bulb so I didn't do any damage. The black/white power wires (ac) are they polarity essential?. The pins read P1d and P1e. I don't know which is load and which is line. I have black to P1d. I tested motor to 12V battery and it runs fine. I was thinking the PWM has a short. Can you offer any ideas? I have been asking life fitness for a controller board schematic for over a year to no avail. Thanks
 

bwilliams60

Joined Nov 18, 2012
1,325
Yes. Do you have much experience with a DVOM and electronics? Have you checked both fuses to start with? Have you checked the DC voltage across the large caps? You can pick this up off of the rectifier as well. If you are not familiar with what I am talking about or you feel uncomfortable working with mains voltage, please do not do this as it can result in death. This is not something to play around with. Give it to an experienced person.
If you are going to do it, you should use an isolation transformer and connect the DVOM first and then turn the circuit on, take your reading and then turn it off. Allows lots of time for the capacitors to power down.
 

Thread Starter

tigerlineman

Joined Nov 27, 2015
14
i built a guitar amp so I am reasonably familiar with large caps. I replaced the bridge rectifier and the 4 IGBTs. I tested both line load fuses. I get 4 volts, 8 volts and 12 (actually 11.2 volts should be 12) at P3 which goes to the display board. When i measure the rectifier i get 28 volts AC coming from the black box switch. (on the side it says ,as does the data sheet 120 v AC in 28 v DC out) I can't seem to pick up DC voltage coming out of caps. How should i measure them? I built a current limiter and have a AC voltage transformer but no isolation transformer. i get 4 and 8 volts dc out of TP 2 and 3 but no voltage out of the TP 5 the 5 volt and TP 8 the 8 volt TP. Where is the 7805? thank you both for helping
 

bwilliams60

Joined Nov 18, 2012
1,325
Sounds about right. Have you checked all the smaller fuses around the board? As for the capacitor voltage, you should be able to take your DC meter across any of the large caps but it sounds like you have proper voltage down the line so should be good. Does the motor connect to the board at P3? Can you post a good picture of the backside of the board? Can you also post pictures of the motor and wiring to the motor? Have you checked the thermal wiring to the motor and made sure all connections to the motor are 100%?
 
Last edited:

Thread Starter

tigerlineman

Joined Nov 27, 2015
14
image.jpeg
Sounds about right. Have you checked all the smaller fuses around the board? As for the capacitor voltage, you should be able to take your DC meter across any of the large caps but it sounds like you have proper voltage down the line so should be good. Does the motor connect to the board at P3? Can you post a good picture of the backside of the board? Can you also post pictures of the motor and wiring to the motor? Have you checked the thermal wiring to the motor and made sure all connections to the motor are 100%?
Sounds about right. Have you checked all the smaller fuses around the board? As for the capacitor voltage, you should be able to take your DC meter across any of the large caps but it sounds like you have proper voltage down the line so should be good. Does the motor connect to the board at P3? Can you post a good picture of the backside of the board? Can you also post pictures of the motor and wiring to the motor? Have you checked the thermal wiring to the motor and made sure all connections to the motor are 100%?
image.jpeg image.jpeg image.jpeg image.jpeg
 

Thread Starter

tigerlineman

Joined Nov 27, 2015
14
Here is back side of board there is a jumper on top that connects pos and neg large caps don't get why that doesn't short it. any chance i put rectifier in reverse? the AC connections match but it looks like pos and neg DC do not. also i don't get DC reading on caps i was trying to trace AC circuit cut continuity failed at a coil/choke on top the bad solders at heat sinks were where i took them out and put back in to check will send motor picts but it works and looks brand new my short occurred at the IGBTs and i replaced them
 

bwilliams60

Joined Nov 18, 2012
1,325
Do you know the part number on the bridge rectifier? I can't be 100% sure but if you have marked them the way you see it, I believe the rectifier is placed incorrectly? If I see it right, you have the mains filter caps hooked to the DC side of the rectifier. Can you verify. Also wondering about lack of solder on right side of board(Mosfets?) What are the part numbers on those?
 

Thread Starter

tigerlineman

Joined Nov 27, 2015
14
Do you know the part number on the bridge rectifier? I can't be 100% sure but if you have marked them the way you see it, I believe the rectifier is placed incorrectly? If I see it right, you have the mains filter caps hooked to the DC side of the rectifier. Can you verify. Also wondering about lack of solder on right side of board(Mosfets?) What are the part numbers on those?
part number is
GBPC3504W i took it out and the way the pins are configured it can only go in one way its just that when i trace it on the bottom of theboard the ~ ac markings line up but the DC+ looks like it goes to the 5 pin jumper cables the last one on the end that goes to no where and the negative goes to the positive on the large caps and that doesn't make any sense also the jumper appears to jump both the positive and negative terminals on the four large caps
 

bwilliams60

Joined Nov 18, 2012
1,325
Just so we are clear. The bridge rectifier was located on the underside of the board and is the exact same part as what you replaced. Why was it replaced?
The IGBT's were replaced with exactly the same part numbers. Why were they replaced?
What did the service guy tell you was wrong or was he the one that did this work?
 

Thread Starter

tigerlineman

Joined Nov 27, 2015
14
Just so we are clear. The bridge rectifier was located on the underside of the board and is the exact same part as what you replaced. Why was it replaced?
The IGBT's were replaced with exactly the same part numbers. Why were they replaced?
What did the service guy tell you was wrong or was he the one that did this work?
Same rectifier I had an electrical storm. No juice to the display board. I replaced rectifier got DC voltage and display screen but then the igbt,s fried. I replaced them an put the board back. All light light up. I connected each wire to biard one by one. When I connected the thermal wires to the motor without the motor positive negative wires connected, I got a current limiter short. This time I I checked the thermal pins and there is no voltage to them. I replaced a .500 ohm sensing resistor that I thought may be bad. The service guy just said replace the board. I have fixed a lot I'm getting closer.
 
Top