Electronics Advice - Treadmill died

[Art Mulder]

Good Morning, Creekers!

Couple of days ago my wife was running on the Treadmill when there was a "pop" and and it abruptly stopped. I was in the room at the time, and heard it. Afterwards, there was a slight burning smell.

It is a Tempo Fitness 620t - just over 4 yrs old. The motor has 5 year warranty coverage, but I don't believe the motor is the issue.

Here's what I've figured out so far, and I would appreciate any advice or pointers that folks more educated in electronics could pass along...


I have verified that there is power at the outlet
The treadmill is completely dead - no lights, nothing on the display panel up top, no sounds, no movement of the belt motor, or of the incline motor, nothing at all.
I popped the cover off of the motor/electronics. I checked and verified that there is power entering the main circuit board (so the on-off switch and the fuse/breaker are fine)
There are about 6 capacitors on the circuit board of varying size. None of them appear to be bulging or leaking
There are no obvious scorch or burn marks. No wires appear broken or melted


That's about all I can see.
Can anyone suggest any other things I can investigate?

I don't think that the motor is the issue; since there is no power at all on the display, I am thinking that the issue is in the electronics somewhere.

I'd hate to toss this out when both motors and the body are in fine shape, but I'm not sure how else to proceed.

thanks,
...art

[Tim Boger]

Regardless of the warranties "specifics", so long as it is still under warranty you'd be smart to contact the manufacturer before you do something that may void it.

Tim

[Dan Friedrichs]

I was going to suggest looking for an electrolytic capacitor that popped until you said you didn't find any. The next most likely failure would be a transistor of some sort - look around at the larger transistors, CAREFULLY looking for small chunks missing out of the packages, holes in the sides, etc. If you smelled burning electronics, it's likely that something blew up enough to break its case, in some way - I'd suggest very, very carefully looking for a part that is cracked, chipped, etc.

[Ken Fitzgerald]

I agree with Dan.....if you heard a "pop" and smelled something burning, there should be some evidence of it.....Take a bright light of some kind and inspect the circuit board very carefully.

[Jerome Hanby]

Tell her it will have to be replaced then tear into it as the start of your shop made drum sander project!

[David G Baker]

If you have some young children in your house encourage them to help you look for the bad component, their eyes are so much better than ours. Worked for me when I repaired cameras at home years ago. If I dropped a tiny part on the floor and couldn't find it, I brought in the pros. Try using your nose, you may be able to sniff out the area where the component is located.
Most treadmills have DC motors in them, check out the area where the AC is converted to DC, it could be a diode that fried. If all else fails you may be able to use the DC motor for something other than powering your treadmill.

[Art Mulder]

I was going to suggest looking for an electrolytic capacitor that popped until you said you didn't find any. The next most likely failure would be a transistor of some sort - look around at the larger transistors, CAREFULLY looking for small chunks missing out of the packages, holes in the sides, etc. If you smelled burning electronics, it's likely that something blew up enough to break its case, in some way - I'd suggest very, very carefully looking for a part that is cracked, chipped, etc.

I'll look again...

1- Overall shot of the front end of the treadmill. Electronics on the left. Incline motor in the middle, belt motor on the right. Cord plugs in on the lower-left
185961

2- closeup of the electronics - power enters on the botto-left (black/white wires). Power to the belt motor goes out on the top-left (black/red wires). Power to the incline motor on the bottom-right (white/red/black harness). Connection to the upper control panel is the cluster of wires at the top-right corner
185962

3- same board from the other side
185963


I think I need to work on my "autofocus"...

[Ken Fitzgerald]

Art,

I went to the manufacturer's website. Based on what I read there, it could be something on the console board that is preventing it from working. Have you looked on the console board for a burnt component?

[Art Mulder]

Art,

I went to the manufacturer's website. Based on what I read there, it could be something on the console board that is preventing it from working. Have you looked on the console board for a burnt component?

I dunno, Ken... I looked at that board also, and it also doesn't seem to have any bad spots visible...
186001 186002

[Ken Fitzgerald]

Art,

Can you sniff around.......try to locate the source of the burning smell you smelled when you heard the pop.

Sniff near the motor.....the boards....... You typically can smell the burnt component even after the event.

[Art Mulder]

Art,

Can you sniff around.......try to locate the source of the burning smell you smelled when you heard the pop.

Sniff near the motor.....the boards....... You typically can smell the burnt component even after the event.


Thanks for your persistence, Ken! Unfortunately the nose isn't finding anything... :-(

On another board I've heard the advice to replace the whole board, which will run about $200, and someone else thought it might be the "Bridge Rectifier"... Boy I wish my EE college roommate lived closer than 4 hrs away! ;-)

[Ken Fitzgerald]

Art,

I will look to see if I can find some schematics for that machine and be of further assistance. If I lived closer, me and my DVM would be there now.

[Art Mulder]

Well the motor is likely fine -- Disconnected the motor and hooked up the leads to a multimeter, spin the motor and I get DC voltage out. (Horizon tech support suggested that test)

So it's likely that motor control board. Tried checking the rectifier but can't really tell. AC goes in, and DC appears to come out, but darned if I could find pinouts anywhere on the net (# MP3510S bridge rectifier), so I could be checking the wrong leads.
I don't like the idea of forking out $200 for an entire new controller board (#SJED08085AA, Sears parts website says it is equivalent to #039679-AA), but that seems the leading solution so far.

Gonna sit on it or a few days...

[Ken Fitzgerald]

Art,

Did you actually measure AC going in and DC coming out of the rectifier?

I'll see if I can find a pinout of the MP3510S bridge...but you would have to remove it from the circuit to get an accurate check on it.

[Jim Koepke]

I'll see if I can find a pinout of the MP3510S bridge

A Google search shows a few sources for data sheets on this.

This will take the AC line and rectify it.

If there isn't a transformer, then there are likely voltage regulators or SCRs in the circuit to run the rest of the components.

The SCRs may be controlled by a lower voltage that also drives the display and lights. If this is the case, the loss of low voltage would explain why everything is dead.

Just looking around to see if a schematic is on line I found Fitness repair parts dot com that has the board for a little less than Sears.

This is the kind of thing that I would try to repair if it were mine, or if you were closer would be willing to look at for a beer or two.

Do you have any electronic techie friends?

Your description of the, "pop, sudden stop and burning smell" tells me a component failed. The pop is made by sudden expansion, usually by extreme heat. The failure of a semi conductor can be difficult to see from the outside. Often the evidence is very subtle. Look for signs of heat, cracks or small sliver of metal leaking out of the plastic case of a component.

One problem with this kind of equipment, the more bells and whistles, the more places for the problem to occur.

jtk

[Art Mulder]

Art,

Did you actually measure AC going in and DC coming out of the rectifier?

I'll see if I can find a pinout of the MP3510S bridge...but you would have to remove it from the circuit to get an accurate check on it.

Ken, I took a much better lit and focussed snapshot:
186410

I was told that the +/- indicate that the DC is on the two outer pins. On those I measured 12-14v (it floated a bit, probably because it is hard to hold the meter leads still) I also measured 120vAC from the two middle pins.

[Dan Friedrichs]

I really doubt that it was the bridge - those things are so cheap no one even tries to undersize them :) And if you have AC in two of the legs and DC out the other two, it's working (you don't even need to pull it out of the circuit to check).

I'd look at anything mounted to a heatsink. Like, it looks like a few parts are clamped to a big heatsink on the side, there. If you're up for desoldering them and seeing if you can read a part number off of them, some simple ohmmeter testing might be able to figure out if those bigger parts (likely transistors...) are what blew.

[Dan Friedrichs]

I guess we were typing at the same time, Art.

If you measured 120VAC across the middle pins, then 12-14 VDC (are you sure you switched the meter to DC?) across the outer pins, that's bad. You should have 170VDC across the outer pins.

If you are sure that there is really only 12-14VDC on the output of that bridge, I would suggest desoldering it, and then with the diode check function on a multimeter, you can tell for sure if the bridge is bad or not. If it's the bridge, it'll be <$5 to fix.

[Don McManus]

I used to be an EE, but i got better. Didnt do much with motors, but here's my guesses...

The pop, then abrupt stop sounds like breaker. But they usually don't smell, (i think...unless ,maybe, the overload on the motor was caused by something jamming up the belt). If the belt isnt dragging/ burning, could be either electronics or motor. Can you "spin it by hand"? I know treadmills dont exactly freewheel, but look around for something frayed/stuck where it dont belong. YOu said you measured voltage at the board, so i'm assuming there's no GFI, or breaker box issue(could try another outlet, just in case)

in the order i thought of them....not necessarily the order i'd try 'em

1) Push the breaker on the treadmill, (yes again). Push it firmly. Pull it out and push it in just to make sure(I've seen a rocker breaker need this to reset...after all the boards and pieces were already spread out on the floor )

2) with power off(for several minutes) , inspect around the leads of the diodes/transistors(big black chunks with thick silver leads/wires). Sometimes the hot component will brown teh circuit board around the leads as the heat is conductor down them.. Rub your fingertip on them one at a time, and smell the fingertip after each one. Whichever one smells worst is closer to the "eruption". If its bad, you may feel or see the debris or damage.

If you have a Kill-A-watt, or Watts-up home power meter, see if its drawing any power at all. If the cord is getting hot, this probably isnt necessary.

2)if you have a voltmeter and are feeling adventurous, you can check that bridge rectifier, measure AC volts across the two terminals marked with an "~". This should be the AC input. And the + and the - should be a mostly DC volts on the + and - terminals. (be careful, the either voltage may be quite high , )

-Can you spin that flywheel in the pics by hand(with power OFF!)

3)The motor is likely DC. Disconnect its wires, then see if the upper control panel will light up(motor shorted would kill the PSU).

4) Check the motor nameplate for model/specs. Measure motor resistance(ohms) to see if its shorted out. If not, and it is a low voltage DC motor, maybe you can try spinning it with a smallish 12V battery(think UPS, cordless drill, kids toy Jeep etc) I would avoid trying a car battery...might get real hot, real fast.

5) is there another breaker? on the motors? under neath? on the rear? A thermal fuse somewhere? GFi in the cord?

6) is the "dont fall off the treadmill" safety tether switch working?

Just some ideas.. the pics are a little fuzzy for more than guessing.

Maybe keep an eye out on Craigslist for someone throwing a similar model out with a bad belt or something. You can swap parts in and out.

A high res pic of the bottom power supply board might reveal something more to us

Good luck,
Don

[Don McManus]

I took too long to answer..lol. Motor sounds like its not shorted.

Here's data sheet for the bridge. www.rectron.com/data_sheets/mp3505-3510.pdf (http://www.sawmillcreek.org/www.rectron.com/data_sheets/mp3505-3510.pdf)

It indicates that the positve DC out "+" terminal is the chamfered or truncated corner. "-" will be directly opposite. And the two adjacent terminals will be "~" for AC input.

[Don McManus]

Nevermind that datasheet i mentioned, its for a more standrard 3510 package. I couldn't find.the side wired one... Luckily yours is labelled.

As was said above, you have to measure the output on DC volts setting. THough there could maybe be 12V of AC ripple on top of the 170 DC volts you'd expect.

What that component with the brown dirt on it in the middle?

[Art Mulder]

If you measured 120VAC across the middle pins, then 12-14 VDC (are you sure you switched the meter to DC?) across the outer pins, that's bad. You should have 170VDC across the outer pins.

If you are sure that there is really only 12-14VDC on the output of that bridge, I would suggest desoldering it, and then with the diode check function on a multimeter, you can tell for sure if the bridge is bad or not. If it's the bridge, it'll be <$5 to fix.

Just went and checked again. Yes, the meter is set correctly to VDC (I borrowed a Fluke 12 from work, I think it's good brand/model). The DC voltage gradually climbed up to 22.8VDC over the course of 3-4 and sat there. I stayed on for a couple minutes to be sure it was settled.



Nevermind that datasheet i mentioned, its for a more standrard 3510 package. I couldn't find.the side wired one... Luckily yours is labelled.

As was said above, you have to measure the output on DC volts setting. THough there could maybe be 12V of AC ripple on top of the 170 DC volts you'd expect.

What that component with the brown dirt on it in the middle?

That is actually not dirt, but a photo artifact. Looks like a like sheen in real life.
It is a "RS207", another rectifier.

[Dan Friedrichs]

Definitely something wrong there, Art. You should definitely have 170VDC (120Vrms has a peak of 170V) on the output of the bridge. I'd de-solder it, and check it with the Fluke set to "diode check". The bridge is just 4 diodes - if you pull up the Wikipedia article on "diode bridge", you'll see how they're connected and how to test them.

[Art Mulder]

Time to bring some closure to this. I hope that this might help someone else having a similar problem in the future...

I removed the big rectifier, which was NOT easy. That solder does NOT melt very easily. (I think the iron I used was a bit old with a tip that was a bit oxidized.) But I got it off. However, when I tested it off the board, it tested okay -- I found an online web page that gave instructions on testing a rectifier. So I then looked at that smaller rectifier. I think Don must have been exhibiting some ESP, since the small rectifier tested as bad while still on the board. So I de-soldered it and confirmed that it tested bad. (And no, I don't remember the details.)

We have an electronics parts place here in town, and my wife took the two rectifiers in to get replacements. Unfortunately they were not stock items, so the guy ordered us the small rectifier. He could not find a supplier for the big rectifier. I wasn't surprised, because when I googled the big one, I kept finding rectifiers with a FAR different package -- they had the pins coming out of the large back, in a square arrangement, rather than in a row out the narrow end. Well the big rectifier had tested as good, so I figured I could always put it back.

A new rectifier cost me about $1.90 plus tax. Though it took a week to get the part.

So about a week ago I put the two parts back on the board, and reinstalled the board in the treadmill, flipped the switch and ... nothing. :mad:
I didn't know WHAT to do next.

This morning I thought I would take one more look. I wondered if maybe there was a bad capacitor that I had missed, so I double checked everything. I also wondered if my soldering job was maybe a bit sloppy, so I took a real close look at that also. I checked to make sure I had not crossed any traces, or that any solder was touching more than one pin of the two rectifiers. I cleaned things up a bit, but still nothing.

And this is where my non-electronics background was hurting me.

As I was looking at things one last time, I noticed the traces that lead up to the small rectifier. They were almost COMPLETELY gone. I don't think I had scratched them up, but maybe they burned off when the treadmill originally failed. I crossed my fingers and obtained some appropriate wire, and soldered it in, to bridge the gap in the traces on the circuit board.

This time, the treadmill fired up just like it always had. What a relief.
So, a lot of headaches, a lot of learning :D and I spent $2 on parts, rather than $200 on a replacement power supply, or $500 on a new treadmill (if I got it on sale) or $1000 on a new treadmill if it wasn't on sale).

Here's some photo shots. If you look at the closeup you can see the difference in the burned-away traces.
190840 190839

[Dan Friedrichs]

Wow! Good catch.

[Brian Elfert]

For future reference, there are companies out there that will do board level repair of treadmill controller boards. The problem is that if the board is only $200 it may not be worth it. Board repair is going to be around $150 or more with shipping.

I'm dealing with a broken treadmill myself. The motor will sometimes work, but mostly not. I've talked with the company techs a half dozen times in the past week. They are saying the motor control board is bad, but I suspect the motor. I'm getting voltage out to the motor from the board so I think the board is fine. I need to figure out how to check the motor brushes. I don't want to pay $150 for a board repair and find out I really need the motor fixed for $250 instead.

Mine is a commercial treadmill by Star Tech that retails for $3,000 to $4,000 so spending a few bucks is worth it. I might not put money into it if was a $600 treadmill.

[Russ Filtz]

Next time it would be much easier just to stop exercising! ;)