Trying to fix electronics on elliptical trainer

[Randy-B]

Let me start saying I am a barely started beginner with electronics.

I have a Star Trac Edge elliptical 4630 with dead electronics.

I just bought the trainer 2 days ago and started trouble shooting. Previous owner said the trainer did work but would display a "service needed" message. Recently the display and all electronic control stopped working.

I have partially dismantled the trainer and it seems mechanically intact.

Problems I have found so far..

-Dead battery. 6v battery charged by an alternator on the trainer showing 0.65v.
-Alternator, quick initial testing showing no output
-Resistor with a melted connector

Attempts at fixes so far:

-Connect 6v SLA battery to battery leads of the trainer. Battery was around 4.8v at time of initial testing and I was reading around 2.5v on the load control board (main circuit board on the machine). Tested at points on the board labelled +6v and ground. This was done before discovering the burnt resistor connector.


What I need help with:

-Resistor is no longer available from Star Trac, unlikely would have bought from them anyways since prices are obscene. The resistor is labelled with "YESO 0103" and "QR300w0.5[ohm]K" (sorry don't know how to make an ohm symbol).
My inexperience shows here though. I am trying to test the resistor. Using my multimeter I first set it to 2K and tested getting a reading of 0.002ohm. Tried again at the 200 ohm setting and getting 1.0 ohm. On Monday I plan on going to Tobrams Electric supply (TES) and talking to them about resistors and possible replacements for this resistor.

Will try testing the alternator again. IF the alternator is truly blown like I am thinking that would explain why I can't get the display to turn on with a surrogate battery since the trainer does not know it is being used.
Big hope here is that the blown resistor did not kill the board.

Any help or suggestions would be great, even confirmation that I tested the resistor right would be great. Also if you would like any pictures of anything ask and I get them up here.

Thanks in advance for any help you guys can offer.

 

[Randy-B]

Got the wife to assist with a test of the alternator. I was reading around 0.5v at the read and black posts. Removed the cap and it looks like the armature is packed with graphite dust. Guessing the brushes are toast, maybe get lucky and only thing wrong are worn out brushes and they can be replaced...

 

[(*steve*)]

The 300W 0.5Ω resistor is unlikely to be damaged. Your testing seems OK. What you could do is see what your meter reads with the probes shorted on the 200 ohm scale. They may read close to 0.5 ohms.

Your reading of 0.002 on the 2k range means 0.002k, that's 2 ohms But you're reading close to the bottom end on either range, so don't expect a lot!

I imagine this resistor is a big metal thing attached to even more metal. If you have to replace it (and I wouldn't be betting on it at this stage) then here is possible replacement, although a wise person would connect 4 of these in series/parallel for the same effect at less than half the price.

And yeah, I concur with cleaning out the graphite dust in the alternator.

 

[Randy-B]

General picture of current state of the trainer. Display, handlebars, heart rate sensor part of the frame removed from top. All shrouds from the front off. Alternator removed for a good cleaning.

Horrible picture of the main board. Praying this is still okay. If I need to start really looking at this I will get my camera out and take a real picture of it.

Here is the load resistor that I am thinking is dead, well at least the end with the important markings. I am pretty sure the marking should read "DQR" since this seems to be a DQ series resistor from YESO.

This is the important picture since I am questioning the resistor.

I appreciate Steve's response but I am thinking he believes it was a 0.5 OHM resistor. I am reading this as 0.5kilohm, or 500 OHM. Of course I can;t really imagine a scenario where this resistor would fail by losing resistance like I am seeing with my meter.

Repair update...

- Removed the alternator and cleaned out the graphite dust. The brushes are in rough shape and the area the brushes contact is pretty badly worn and scored. Will be reinstalling soon and hoping for the best.

 

[Randy-B]

The 300W 0.5Ω resistor is unlikely to be damaged. Your testing seems OK. What you could do is see what your meter reads with the probes shorted on the 200 ohm scale. They may read close to 0.5 ohms.

Your reading of 0.002 on the 2k range means 0.002k, that's 2 ohms But you're reading close to the bottom end on either range, so don't expect a lot!

I imagine this resistor is a big metal thing attached to even more metal. If you have to replace it (and I wouldn't be betting on it at this stage) then here is possible replacement, although a wise person would connect 4 of these in series/parallel for the same effect at less than half the price.

And yeah, I concur with cleaning out the graphite dust in the alternator.

Thank you for the help. I believe the esistor is a 0.5kilohm resistor though, not a 0.5ohm resistor. I have attached a picture of the markings on the resistor for confirmation.

You are right about the resistance on my meter, it reads around 0.5 ohm (iirc) when shorting the probes.

My concern is that if I am right and this 500ohm resistor only has a resistance of 2.5ohms then what could possibly be burnt out down the line. I know I have a burnt up connector (will get picture of that while reinstalling the alternator).

 

[Randy-B]

Looking at the link you sent me for the resistors. Would I be right in thinking this is the closest to what I have? Also, would this be a suitable replacement?

http://au.rs-online.com/web/p/panel-mount-fixed-resistors/6150606/

Sorry for what is likely a bunch of beginner questions that I should already know, just feel a little lost when dealing with electronics

 

[Randy-B]

Looking at a wire wound load resistor specifically one this style:

How, if possible, would one of these fail causing it to lose resistance?

 

[KrisBlueNZ]

The "K" in the marking means ±10% tolerance. It really is a 0.5Ω resistor!

(A 500Ω resistor would be marked "500Ω", and resistors that are marked in kilohms are marked with "KΩ" not "ΩK".)

 

[Randy-B]

Thank you for the explanation. Will take a better look at when I am back home.

 

[(*steve*)]

And as I said, it's quite unlikely that the resistor is damaged. A wirewound resistor will likely go open circuit when it fails. You are measuring a resistance that seems to be within range for such a resistor (allowing for the resistance of the leads on your multimeter)

Another obvious reason for it being a 0.5 ohm resistor rather than 500 ohms is the power rating. For 300W to be dissipated, a 0.5 ohm resistor only requires just over 12V, a 500 ohm resistor requires over 350 volts. I'm pretty sure you'll find the alternator produces something more like 12V than 350V under load.

 

[Randy-B]

Took another look at the resistor, I am measuring 1 ohm, and considering I am getting 0.5 ohm when shorting the probes, I guess you add them together. So resistor is reading 0.5 ohm like it should.

So off to re assemble basically everything, and take another look at the alternator.

Thanks for eliminating the resistor as an issue.

 

[Randy-B]

Okay, elliptical trainer is fixed. Thank you very much for the help.

I was worried about the alternator still because after cleaning it I hooked it up and tested it at 2.5v, where it should be 9-10v. But Steve said something about alternator voltage under load. So I hooked everything back up, connected my voltmeter to read alternator output.
Well started pedaling and tried a button on the display, and everything lit up. Read the voltage display and reading right around 10v like it should.

SO thank you Steve for the help, will be back with other questions in the near future I am sure.

Thanks again for the help. Saved me a fortune!