MC-60 Motor Controller Repair (Treadmill)

Thread Starter

thearrow

Joined Aug 24, 2010
24
Re-soldered all of the yellow circled connections.
Same behavior.

Got to thinking about this:
Voltage Diagram

The speed control voltages in the bottom right?
I get 11.7 VDC RED to BLACK (Expected 12 VDC)
But I get anywhere from ~9.5 VDC (0 mph) to ~11 VDC (10 mph) WHITE to BLACK.... Isn't that range supposed to be 0-12?
Could the problem be somewhere on the power board and no longer this one?

I also checked the 120 VAC below the motor outputs coming in from the blue and other white. 121.0 VAC.
 
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Thread Starter

thearrow

Joined Aug 24, 2010
24
Further research lead me to this:
MC-60 Mod PDF

Which says:
D7- Labeled SPD CTRL. This LED indicates that the controller is receiving a speed signal from the console. Note that on
consoles without a power board that use a speed pot, the LED will light solidly, but vary in intensity at different speed
settings. On consoles that use a power board, the LED will flicker with the PWM control signal. The brightness of the
LED will vary with the speed setting. NOTE: On consoles with speed potentiometers that require a power board, this
light may be seen to flicker even when speed is set to zero MPH. This is due to a small signal being sent from the
console. MC-60 controllers with this console and power board configuration will have RPS 1 clipped to operate
normally and keep the treadmill from running at all times. If this LED is not lit when the speed is set above zero MPH,
but D11 is, it indicates a problem with the console, power board, or wire harness.
However, on my board, no matter what (when I have all the wires plugged in) the SPD CNTL LED is always glowing steadily (no flickering, no difference with different speeds)........ I tried running with RPS 1 clipped, which made no difference.


And obviously:
D6- Labeled SCR. Indicates that the SCR is triggering on the controller. If this light is out, no voltage will be sent to the
motor. Note that this LED will vary in brightness, depending on the speed setting. If this LED does not light when the
safety key is inserted and D7 is lit (indicating a speed setting other than zero MPH), the controller will need to be
replaced.
Mine never lights at all (which I'm now guessing has something to do with the speed control...)

Also, a little tidbit - the power board is right under the spot of the liquid spill.....
Could I have a couple of fried ICs on the power board, too?!
 

JoeJester

Joined Apr 26, 2005
4,390
don't forget to clean up the connections around U1 also. R42 doesn't look connected at all.

Do a physical inspection of the whole board. Clean up any suspicious connections.

As far as D6 not being lit, that is the indicator that U3's input is working. That pulsing means U2 section 4 is working ok, but we haven't confirmed anything at the input of that section either. You mentioned the motor's studdering when you touched R7. For the motor to move when you touched R7, everything to the right (on the schematic) of R7 must have worked else the motor wouldn't have moved at all. You also mentioned the Current Limit LED energized. Did any liquid get into the motor?

Clean up the connections.
 

Thread Starter

thearrow

Joined Aug 24, 2010
24
I'm starting to get tired of this.

Cleaned up everything. Everything looks fine top and bottom. Everything is connected. Everything has solder on it.
Paid special attention to the areas around the ICs and R7.
No difference.

I'm 90% sure the motor stayed dry. I tested it with a cordless drill battery earlier and it spins fine.



I'm starting to be concerned about the SPD CNTL light. It seems like it should be blinking along with the PWM light in the power board or changing intensity based on the speed or something other than staying constantly lit like it is now.

Could Q5/Q6/Q7 have gotten fried and need replacing?
Could something on the power board need replacing?

Can anyone suggest some measurements I could perform with a multimeter to narrow down the problem?
 
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JoeJester

Joined Apr 26, 2005
4,390
Let's work this one at a time ...

Two questions:

Set the speed control to midway. What is the voltage at U1 pin 5 referenced to ground. This voltage represents the over-current reading. If necessary, set your meter to a scale to read milli-volts.

Keep the speed control at midway. What is the reading at R18, the side that is not connected to Q5.
 
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Thread Starter

thearrow

Joined Aug 24, 2010
24
Thanks for taking the time to try to help!

I'm confused.
Is this AC Voltage I should be measuring?
I assumed it should be DC, so I tried that first. DC voltage measurements just jump all over the place....
Also, I should be putting the negative/common/black probe of my multimeter on the ground and the red/positive one on the place being tested? Basic questions, I know, but I want to make sure I'm doing everything right.

(5 mph)
DC reading was jumping all over the place 0-100mV-50mV-120mV
AC reading was steady 6.7 V

I'll go try to find the R18 measurement now.

EDIT:
Now I'm utterly confused. At 5mph again the AC reading for pin 5 of U1 to ground was 8.3 V.... (why did it change?)
At 5mph AC from R18 (not connected to Q5) to ground was 7.8 V....




On a side note, where would be a resource you recommend for learning to read and get familiar with a schematic like the one for this controller? Or just electronics in general? I've skimmed over the resources at this site, perhaps that would be a place to start? I'm familiar with the basic symbols and measurements and such, but I feel like I'm quite ignorant of the big picture. (A book / webpage perhaps?)

Thanks!
 
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JoeJester

Joined Apr 26, 2005
4,390
Just to learn the symbols you can search for electronic sysmbols.

Tell me about the motor... what is the voltage rating and current rating? The schematic I'm working from is lacking in a few details.

The problem we have is we are looking at pulsating DC signals with a multimeter. If we use 50% as the duty cycle, the AC reading will be approximately 6 volts, that is why I had you set the speed control to half-way.

On to the Q5 .... if you measure the collector to ground (the point where the cathode of the LED connects to Q5) you should read something. If you read zero, place your meter on the side of R17 that is not connected to the LED. You should read 12V there ... 11.7 is good too. If the 12V is there, power down and test the LED using the diode function of the meter. If the collector reads a steady 12V, and the LED tests good, then Q5 is probably defective.

I am concerned that the Current Limit signal. 6.7 volts across a 0.62 ohm resistor is high enough to trigger the current limit circuit. I was expecting less than 60 millivolts.

You said you tested the motor. Was that under load (connected to the treadmill)? Does the tread move easily if you turn the motor by hand? We could disconnect the drive belt to make sure the motor turns with the control if necessary.
Is the motor getting warm while it is stalled?

on edit ... disconnect the power and measure R28, the 0.06 ohm resistor.
 
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tvmanjon

Joined Feb 5, 2010
5
Did you get this going yet? If not let me know I repair these almost daily. Know them inside out. Cut resistors are like that from the factory. (RPS1,2,,3 and R 37 6/8mph). With ac only applied 12v led will be lit. Im the mc70repairexpert
 

slamtweel

Joined Oct 7, 2010
1
Does anyone know what the component (and values) of the item between C16 and D4? This piece is burned beyond recognition on my board. Thank You in advance.
 

deadpoet

Joined Jan 1, 2011
1
On some of the MC-60 SCR boards the RPS 1, 2, or 3. may be clipped straight from the factory. It all depends on the application of the board. Resoldering RPS 1 and 2 may be your problem with the Curr Lim light. The Rev of the board will tell you which ones need to be clipped. This file will will give you all the information you need about the MC-60 and its RPS variations.http://www.cnczone.com/forums/attachment.php?attachmentid=43586&d=1189715613
Hope it helps
 
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RugbyMon

Joined Mar 11, 2011
1
Hi everyone. The youth pastor at my church brought me the control board for his wife's treadmill. It is missing Resistor R42. Does anyone know the value. I cannot find a schematic. Once I know I can take it to work and solder in a new one. Then hook up some power and an O'Scope and start figuring out how this puppy works! :) BTW worst case scenerio and I blow it up anyone out there rebuild these? :eek:
 

Mongoose9

Joined Aug 30, 2011
1
Sorry to dig up an old thread but I was using the photos in this thread to repair a board. The photos seem to have been taken down in the past few days though. Does anyone have them? I mainly need the value of resistor R56. It's the resistor next to the two black transistors in the corner. I found a google cache of one of the photos but it's a bit fuzzy. It looks like a 25M ohm resistor but that seems high? The bands are Red Green Blue Gold.
 

raytodd

Joined Sep 30, 2011
2
I have a proform pt 6.0 with the same mc 60 controller board. the RPS 1 resister has one cut lead looks as though done during manufacturig. treadmill has been fine for a long time and i'm the only one who's been inside. Thinking maybe depending on application whether RSP 1 is used or not. the lead definitly looks cut not broken.

Me myself am trying to figure out how much AC( dc voltage ripple) should or should not be on motor leads. With ac meter have 16vac at 1mph and up to 30vac at 7mph with 70vdc at same time. Don't know if i'm reading a pusating dc voltage that is supposed to be there or not. Now very resently an ac hum started comimng from belt drive motor. And also started triping 15 amp circuit breaker. Can't seem to find specs on the board so i don't know what i should be reading. I'm brand new to this forum thing. but if anyone have any advise would be greatly appreciated
 

manish121

Joined Mar 27, 2012
1
Tom i am trying to contact you for some help but from another forum

http://www.badcaps.net/forum/showthread.php?t=19027&highlight=lg+50
link
http://www.badcaps.net/forum/showthread.php?t=19027&highlight=lg+50
are you the same tom66 from badcaps.net?

if so I wanted to know if there was a fix for that post as i have the same issues with my LG 50PK350


I could not register on badcaps for some reason and thought. I also tried private msg to you from here but it would not let me.

sorry for contacting yoy like this.


Thanks Manish
 
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