I admire the tenacity of some who have out of desperation traced out their control board and were able to repair it. Unfortunately I am not sure I have the required time in order to do this. My motor will not run at all but think the motor is okay. The controller board was made in China as with all control boards these days and unfortunately no schematics are available. They only want to sell new boards and of course they are usually quite expensive if even available. My treadmill has two identifiers on it in addition to the Sears ID plate. It has MST and Lifestyler 2800 on it. It has been kind of indicated to me that the treadmill was mfg by IconFitness. I was just wondering if any other has had any experience in troubleshooting a Sears Lifestyler treadmill board. I could send a pix of the board. The board has four rheostats mounted on it and also has five heat sinked three wire transistors or scrs, not sure which.
Just Me/Lee

 

After some searches, it appears that your treadmill uses the MC-60 controller board.

Have a look at this thread:
http://forum.allaboutcircuits.com/showthread.php?t=18895

In the 1st reply (post #2), trolley1 attached a hand-drawn schematic of the MC-60 controller board.

 

Thanks for your reply. I am a little confused by your reply however. You state I should start a thread/topic. I thought that is what I did when I opened this thread for a Sears treadmill schematic. Yes my board is similar to the MC-60 but not exactly the same. My board # is MAG-MC-30 and was mfg in China by Magnetic Electronics Ltd. Haven't worked on a treadmill board before, so I am puzzled by a few things and wondering if you can shed any light. Nice to know we have an expert available.
From the schematic I cannot tell where the +12v is generated from. Also I cannot determine where the pulses are being generated from. One other question is that there is no LED on my board. The U3 chip (3021) goes from pin 2 to a diode instead of an LED. If you can help me out a little on these answers I sure would appreciate it.
Lee
p.s. I checked all the SCR's and they seem okay. I do have 12 volts but where does it come from? I have not hooked up the scope yet to see if I have any pulses. What is the pulse generator comprised of. Is it op-amp 3 & 4? Tomorrow I will check to see if the generator is working. I only have one transistor on the controller board and it is Q4. Does the pulse generator always run or is it turned on & off by something? Sorry for all the questions.
Lee

 

I am a little confused by your reply however. You state I should start a thread/topic. I thought that is what I did when I opened this thread for a Sears treadmill schematic.

That is simply my signature line.
I've been a member here for a number of years, and the more I posted, the more PM's and E-mails I received with requests for off-list assistance with their projects; I became so inundated with these requests that I had to disable both my PMs and E-mail from this website. As a result, I composed my signature line with the intent of dissuading people from sending me PM's and E-mails. For the most part, it has worked.

Yes my board is similar to the MC-60 but not exactly the same. My board # is MAG-MC-30 and was mfg in China by Magnetic Electronics Ltd.

I see. Apparently, they used several different controller boards in that same model.

Haven't worked on a treadmill board before, so I am puzzled by a few things and wondering if you can shed any light. Nice to know we have an expert available.

I am not the only one here who is capable of troubleshooting such things. I just post a lot.

From the schematic I cannot tell where the +12v is generated from.

There should be a transformer and rectifier bridge somewhere - or it could be a switching supply. In order to be of assistance, we will need for you to take detailed, well-focused and well-lit photos that you can post on the Forum. This is more difficult to do than it sounds. The best lighting you can get for such photography is outdoors on an overcast day, as the light is bright and very even; there are no harsh shadows. Photos taken with flash attachments, under incandescent lighting, or outside on a clear day have too much contrast, making the details nearly impossible to see.

Also I cannot determine where the pulses are being generated from.

We're going to need those photos.

One other question is that there is no LED on my board.

OK, so it's a board designed to be cheaper than the M-60 controller.

The U3 chip (3021) goes from pin 2 to a diode instead of an LED.

Here's an older datasheet for the MOC302x series triac drivers:
http://www.soselectronic.hu/a_info/resource/d/moc302x.pdf
They might have used a diode instead of an LED because it was cheaper. On the other hand, they might have used a rectifier diode because it would be more reliable than an LED (having a significantly higher current rating, it would be more likely to survive transients on the supply).

I checked all the SCR's and they seem okay. I do have 12 volts but where does it come from?

I see where it's coming from; R9, right off the mains power. That is not good. R9 would allow ~21mA current to flow, and it would dissipate ~2.33W power.

I have not hooked up the scope yet to see if I have any pulses.

That would be a good place to start. Does anything on that controller look like the M-60 schematic?

What is the pulse generator comprised of. Is it op-amp 3 & 4?

I had never really looked at the M-60 schematic in detail; there was no reason for me to do so. It might be worthwhile to see about making a simulation of it, but that will take a bit of time.

The pulses actually come from the mains. It isn't a PWM controller; it's a TRIAC or SCR controller. It works sort of like a dimmer.

Tomorrow I will check to see if the generator is working.

Pulse generator, you mean? [eta] There isn't a pulse generator, per se - it's just a zero crossing detector.

I only have one transistor on the controller board and it is Q4.

You should have a signal on the collector of Q4 that is roughly twice the frequency of your mains power; so either 100Hz or 120Hz. The pulse occurs at the mains zero crossing point. It should be a brief positive pulse, somewhere in the neighborhood of 0.4mS if mains is 60Hz, or roughly 0.5mS if mains is 50Hz.

Does the pulse generator always run or is it turned on & off by something?

As long as the treadmill board is powered up, there should be a pulse on the collector of Q4, and also on U2-4 pin 9. If that is good, then it's time to look at U2-4 pin 8. The pulse width there should depend upon the speed setting and the motor current.

 

Sgt you seem to be very knowledgeable so I fully understand why you would be inundated with emails etc. thus I fully appreciate the time you are taking to answer my posts.
1. Regarding the power supply Sgt I think I see now how it is derived and failed to notice before when it is quite clear. That part of my board is basically the same as the MC-60. There are two diodes off of the 120vac line which goes to a 7.5K ohm resistor (5k on the MC-60 board) then through another diode and a 12v zener diode & capacitor (C7) on my board. I do not have an LED to determine whether the 15v is present like the MC-60 board. I think I would be wise to install one as it is a good indicator that at least the 15v supply is working properly.
2. Q4 transistor: I was thinking that U1 amp #4 was the pulse generator but maybe I was wrong. You say the pulse is coming from the collector of Q4. I checked the board out earlier and I did not see much of anything. I only saw one pulse and it was a negative pulse which doesn’t make sense. I will have to check it out again tomorrow on the collector of Q4. But if U1 amp #4 is not the generator then how does the speed control regulate the speed of the motor??
My Q4 base goes directly to pin 5 of Q1 or U1 which doesn’t seem to make much sense. The collector goes to pin 11 of U1 or A- (gnd).
Didn’t have much time to look any further today. Why does one pursue something like this? We electronic guys must be all nuts I think!
I took one picture and will try to attach it is I can figure out how to use the website.
Lee
p.s. I do not know how to add a picture to this post. I have a picture on my desktop but do not know how to insert it since there seems to be no way to do that. I am only given a choice to add a URL.

 

1. Regarding the power supply Sgt I think I see now how it is derived and failed to notice before when it is quite clear. That part of my board is basically the same as the MC-60. There are two diodes off of the 120vac line which goes to a 7.5K ohm resistor (5k on the MC-60 board) then through another diode and a 12v zener diode & capacitor (C7) on my board.

OK, so 120vac-12v/7.5k~=14.4mA total current available from the 12v supply.

I do not have an LED to determine whether the 15v is present like the MC-60 board. I think I would be wise to install one as it is a good indicator that at least the 15v supply is working properly.

You only have 14.4mA total available to work with. If you add an LED, it will likely pull the main supply down.

Have you verified that you have 12v available at the Zener?

2. Q4 transistor: I was thinking that U1 amp #4 was the pulse generator but maybe I was wrong. You say the pulse is coming from the collector of Q4. I checked the board out earlier and I did not see much of anything. I only saw one pulse and it was a negative pulse which doesn’t make sense. I will have to check it out again tomorrow on the collector of Q4. But if U1 amp #4 is not the generator then how does the speed control regulate the speed of the motor??

I've been working on putting together a simulation for the M-60 controller board; it's not finished, as you can see in the attached image; I don't have a model for the MOC SCR driver; I'd thrown a bridge rectifier in temporarily - and there are a number of other details that need to be sussed out. The schematic left in the other thread wasn't bad, but there are some notes that are meaningless to me, and lot of reference designators and component values were omitted. I've had to make some guesses - until I can start to see how it all fits together.

As building and debugging a simulation that has so many components is rather time and labor intensive, and so many other people have needed help, I try to balance my time between this and a few dozen other projects going on.

My Q4 base goes directly to pin 5 of Q1 or U1 which doesn’t seem to make much sense.

Ahhh, which is it?
"Q1" would denote a transistor, mosfet or SCR/TRIAC; usually a 3-legged critter.
"U1" would be some other type of IC. Does your U1 have a part number?
If a quad opamp, like an LM324, pin 5 would be the noninverting (+) input of channel 2/B, and pin 11 would be ground.

The collector goes to pin 11 of U1 or A- (gnd).
Didn’t have much time to look any further today. Why does one pursue something like this? We electronic guys must be all nuts I think!

Where does the emitter come from/go to? Is it coming from 12v like the M-60 controller does?
Is Q4's part number 2N4403, 2N3906 or 2N2907?

I took one picture and will try to attach it is I can figure out how to use the website.

p.s. I do not know how to add a picture to this post. I have a picture on my desktop but do not know how to insert it since there seems to be no way to do that. I am only given a choice to add a URL.

Below your prior reply, click the "Edit" button.
Then click the "Go Advanced" button.
On the next page, click the "Manage Attachments" button.
You must have popups enabled for this website. When you click the "Manage Attachments" button, you'll get a popup that will have three "Choose File" buttons to upload images from your computer with, and three blank boxes that you can fill in URL's.

Click one of the "Choose File" buttons, navigate to your desktop in the following dialog, and click on the file you want to upload; then click Open.

You'll be returned to the "Manage Attachments" dialog. Click the "Upload files" to the right of the "Choose File" buttons, and your image should upload to the board.

There are size restrictions for images. If your image is too large, it won't go. In that case, you can either put it in .PDF format or add a ".pdf" extension to the end of it, like "myphoto.jpg.pdf". It's not as convenient that way, but at least you can upload it.

 

Okay Sgt will try to answer. Yes I have 12v at the zener.
I have drawn a diagram of the op amp that drives the MOC 3021. After tracing it out I find it a very strange hookup. Not sure just how it is suppose to work. As you see it is quite different from the MC-60.
I get a negative pulse at pin 5 of op amp #2 and that's all I get. Pin #6 of the op amp is at ground with no pulses. So perhaps I have some problem in this area. I need to get you the images. I will try with this message.

Regarding Q1 or U1. On my board it is labeled Q1 but should be U1 to be correct since it is a LM324.
Still not sure I know how to add images but will try.
Lee

 

I must compliment you on the wonderful job that you did taking the photograph of the main board! If only everyone could come that close to perfection, life would be so much easier!

Would it be possible for you to do a repeat performance, for the bottom side of the board? Simply flip the board over carefully, horizontally, and try to photograph it from about the same distance as you did the photo that you just posted. With the 2nd photo added to the 1st, the board connections can be traced out and the circuit will make a good deal more sense.

I can "sort of" see some of the traces through the board, but that is not good enough to recreate the original schematic.

We will also need to go through and verify what the reference designators are (R9, D4, C5, etc) and the values for each part. This will seem somewhat tedious, but it really needs to be done if you want a decent troubleshooting aid.

After the circuit is constructed in the simulator, I can give you a very good idea of what kind of voltages and signals you should be seeing at various places on the board.

 

Wow that would be wonderful! Yes I will take a pix of the backside and try to come up with component values etc.
A friend/Lee

 

That's pretty good I agree.

What camera you use?

 

I just used a cheap Sony CyberShot DSC-W350.
Lee

Here is a photo of the backside

 

I have another photo of the back side of the board and also the resistor list. I will again try to post.