Help with Motor Control Board - ProForm treadmill

[Crrose]

I have a ProForm treadmill and I believe the motor control board went bad. All the functions work except power to the motor. I tested the motor and it is fine. A replacement board cost minimum of $130 so I would like to try to fix myself. Everything looks fine on it except by two resistors where the board turned brown like it was too hot. I tested the resistors continuity and I get a beep so I assume they are fine. The only other thing is at the base of the relay it looks like a water stain or something which you can scrape off. Does anyone know if either of these could be the problem with the motor not getting the power sent to it?

[budm]

Re: Help with Motor Control Board

How many wires are there on the Motor? Can we see how the motor is connected to the PCB?
The more details pictures we have the more clue we will know how it is setup.
More likely dc motor, and those two resistors may be for braking.

[stj]

Re: Help with Motor Control Board

check the parts on the heatsink.

[keeney123]

Re: Help with Motor Control Board

On some of these treadmills they have a safety switch on the control panel. If this switch in not on the power will not go to the motor.

[budm]

Re: Help with Motor Control Board

On some of these treadmills they have a safety switch on the control panel. If this switch in not on the power will not go to the motor.

Good point, may be one on the running board also.

[Crrose]

Re: Help with Motor Control Board

Ok the motor has 4 wires coming from it and it is a DC motor. I hooked an 18 volt drill battery to it and it runs fine. I also checked the safety key, when it is removed all the power to the machine goes off and once I reinsert it the power goes back on. There are 4 wires from the motor 2 blue a black and a red. Black and red go from board to motor, one blue from AC1 on board to motor and the other blue to the other board along with the AC2 white. The only other wires from board to board are the 3 red/wht/blk speed control wires. I included pictures of it all along with the Voltage diagram. The one picture of the bottom of the board is beneath the 2 resistors.

[budm]

Re: Help with Motor Control Board

So the resistance between the two blue wires (for thermal shutoff switch) show <1 Ohm?
What are resistance readings of the DZ1, DZ4 in the over heated area of the two resistors?
Can I also get the straight shot pictures of the whole top and bottom side of that motor control board?
Do you also hear that 24V 30A contact rating even click on, off?

[budm]

Re: Help with Motor Control Board

oops, wrong post.

[stj]

Re: Help with Motor Control Board

i/v worked on stuff like this in the past and it was often the scr's / triacs
so what are the parts on the heatsink?

[Toasty]

Re: Help with Motor Control Board

Does anything light up?

I'd bet your on the right track and there's a problem with the Zener's under the two stand-off power resistors. Could be they're shorted and that might be why you get a beep when testing the resistors. Any values on those resistors?

T

[Crrose]

Re: Help with Motor Control Board

Everything lights up like it is supposed to, the motor just will not go on. I tested the resistance on those 2 diodes and it is 0 but they have continuity. What is the diode below the Zenner. It has 24 C838 written on it, that is all I can see with it on the board.

[selldoor]

Re: Help with Motor Control Board

These things usually come up with an error code E01 E03 E31 and so on
Does yours - then search for the board number and error code?

[Toasty]

Re: Help with Motor Control Board

They're both Zeners.

T

Edit: They should act like diodes. Continuity one way but not the other. You may need to unsolder one leg of each to test correctly.

[Toasty]

Re: Help with Motor Control Board

The black Zener diode is likely a 24v one. Reasons out because the relay is 24vdc. The smaller one is probably a 5v. If you -carefully- read across them with it on and get those voltages, then the basic part of the PSU is okay.

Could the motor have burned out?

T

[stj]

Re: Help with Motor Control Board

these things are pwm drive.
you really need to trace the motor drive back through the board.

[keeney123]

Re: Help with Motor Control Board

I would check AC1 contact blue wire to AC2 contact white wire. To first see if you are getting 120 AC. If not it could be the thermal switch is bad. If you have 120 volts at that point. Then something on the speed control board is bad and a good stop to look at would be were the burn spots go to on the speed board. I have seen SCR (Silicon Control Rectifiers) blown apart when something stops the motor from turning.

[keeney123]

Re: Help with Motor Control Board

Also, check the black, white, and red lines to make sure the speed board is getting +5 VDC red to black and -5 Volts DC white to black. I would think this should be there is everything else powers up but you never know.

[keeney123]

Re: Help with Motor Control Board

Also, check the black, white, and red lines to make sure the speed board is getting +5 VDC red to black and -5 Volts DC white to black. I would think this should be there is everything else powers up but you never know.

I would set the drive motor to as fast as it can go from the main console. Then as slow as it can go. I would expect one voltage reading in one mode and another in the other mode. These are actually pulse width modulation DC. I think these must feed the gate voltages of the SCR telling it when to turn on and for how long. The AC voltage on the speed board must get converted to High Voltage DC which pulsates at a steady rate and when both +5 volts DC and the High voltage DC are low the motor turns off. Perhaps the neg 5 volts is used as a breaking voltage for the motor which turn on a negative going SCR High Voltage DC.

[Crrose]

Re: Help with Motor Control Board

Selldore: There are no error codes that come on. Looks like normal, just doesn't run.

Toasty: The motor is not burnt out, runs when hooked to 18v battery.

Keeney123: I do get 120V on the AC1 and AC2. I will have to re-install the board to measure the black white and red but if I remember correctly I did get a reading from it earlier.

[Crrose]

Re: Help with Motor Control Board

I would set the drive motor to as fast as it can go from the main console. Then as slow as it can go. I would expect one voltage reading in one mode and another in the other mode. These are actually pulse width modulation DC. I think these must feed the gate voltages of the SCR telling it when to turn on and for how long. The AC voltage on the speed board must get converted to High Voltage DC which pulsates at a steady rate and when both +5 volts DC and the High voltage DC are low the motor turns off. Perhaps the neg 5 volts is used as a breaking voltage for the motor which turn on a negative going SCR High Voltage DC.

I will do this tomorrow after I put everything back together. I removed the board from the mounting plate and have to get some heatsink paste.