Hi everyone. I have very limited experience with electronics. I have a slight understanding of some things, but get easily lost when things start to get tricky.

Anyway, I was given a treadmill. It's a pro-form 400c. The control panel to adjust the incline, speed, and program selects works fine. The incline on it works fine too. However, the motor for the platform does nothing. I'm in Ireland where the standard voltage is 240 ac.

So I opened the cover and found the control pcb had a track burned out on it. I uploaded a couple of pics here nd you should be able to see what I mean from a couple of them. The best schematic I found is here .I tested the motor on a car battery and it spun up fine. I even opened it up and cleaned the brushes and armature in case there was a problem with dirt. It's a 130 vdc with the two brushes 180 degrees to each other

I changed one of the IGBTs. The one on the left of the two together, as I thought it may have blown. I repaired the track, and plugged it in. My soldering is not the super best, but it does work There was a pretty big flash, and the fuse switch in the house tripped. The little diode close to the burned out track had blown. Now, I'm just guessing that that little component was a diode. I'm sure someone here can tell me exactly what it is.

I tried a dc multimeter onto the wires to the motor, with the motor unplugged. Then I turn on the machine and I got about 120 v dc , but it dropped down to about 10 in the space of 60 seconds.

On the underside of the board, there is no components or any sign of overheating. But whatever is wrong, it's something I need your help with.

 

I have this, I am not sure how accurate it is as it was a reverse-engineered schematic.
Max.

 

Thanks Max.

Where do you think I would be best looking at to see what component, or components, would be at fault? It's like there's a short in the motor, but there's not.

 

Dang... that really popped bigtime !! Why, is a good question. It has me wondering if the party you got the machine from, was poking around where he shouldn't have, and touched or dropped something conductive into the circuit... I would also wonder what other cascading damage was done by the short...

Pardon, I am equally green in these areas as far as the control board goes, part of my occupation prior to retirement, gave me the op'ty to rebuild treadmill motors, but makes me no expert at any rate...

I shall follow this thread to its conclusion

 

Testing the motor on an automotive battery, although not conclusive give you a good idea of the state of the motor.
It is obviously something on the power input/power out side, Q1 Q2 etc.
I have never seen a set up such as this where there appears to be Both SCR Q1 control of the rectified DC and the motor through Q2?
I would suspect Q2 is switched fully on and then phase angle control is used through Q1?
Take care as the input is not isolated.
Max.

 

It has me wondering if the party you got the machine from, was poking around where he shouldn't have, and touched or dropped something conductive into the circuit... I would also wonder what other cascading damage was done by the short...

I don't know what was done to it. I doubt they did much to it, as you can see in some of my pics the lightly damaged track before I changed the IGBT. The big damage you see now, is as a result of after the change and repair of the track.

Max, I did test the motor on a battery, and as you say, while it's not conclusive, it does pass that "test".

I'm trying to get my head around what you're saying. I think you're right about the fault in the power in/out . With the use of a simple multimeter would I be able to find out which does what? Without having to remove them from the board. It was Q5 that I replaced. Would it be any help if I posted a pic of the underside of the board?

Looking around, the board (MC2100E) Is extremely rare, so maybe it is odly made

 

I found a high res pic of the board if it is any use. The site is in Polish and some guys offer a couple of opinions . http://obrazki.elektroda.pl/6547406800_1326043010.jpg

 

If it was to blow with the motor disconnected, I would first opt for a test of the bridge, if one section was shorted it would be a dead short.
Max.

 

It doesn't short without the motor plugged in.

 

So I've fooled around it for a bit,and reckoned I'd best off build a separate controller for the motor. The more I try and get the board going the more damage I cause to it. It still works everything, except the motor which I had electrical engineer test properly for me I just don't want to send it to the treadmill home in the sky.

I've looked around on building one using a 555 timer. However, almost all ones I've seen are for 12v or less. I know the principle will work the same,but not too sure which components I'd need to change. This is one I reckon I'd manage http://www.dprg.org/tutorials/2005-11a/index.html

Would I be right in saying all I'd need to change is the Mosfet to one that could handle higher voltages ? If so, what one would best suit? Or would I need to change more parts? Or is that circuit not really best suited for what I want to do? .

Thanks for taking the time to read this and for anyones help so far.

 

Unless you intend building one just for the experience, I would look at some of the KB/Baldor types available on ebay etc.
The lower end ones are SCR bridge type, but can be had fairly cheap.
Max.

 

Ger80 - you can buy new PCboard for your treadmill . 2 month ago I replace so device on Nordictrack E3100 - the same .