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Old 08-19-2018, 02:03 PM   #1
davg
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Default Treadmill DC Circuit no motor start

MC-02 Control Board
I picked up a treadmill at a yard sale (was hoping to use the DC Motor and Controller on my drill press) brought it home plugged it in and it worked fine. I removed the motor, controller and the control panel from the frame and tested it on my bench it would not start the motor? I reinstalled it back on the treadmill frame and it still would not start the motor? All the wiring hook-ups was checked and double checked as per the wiring diagram. I must have damaged a component on the board but there is no evidence of that? The board is a MC-02. I checked some of the voltages on the board and recorded the following;
1) 120 VAC across LG4, LG5.
2) 5VDC across LG1 and LG3.
3) No voltage across LG6 & LG7 (To Motor)
4) Ground to LG6 is 54VDC the same on LG7
5) Probes across LD1 is 12VDC (not sure what LD1 is)
6) If I jumper center leg and right leg of Q4 motor will run?
I have no idea what the voltages should be except the 120 VAC and the 5 VDC although 54 VDC seem to be present in many places on the board?
I have no idea what happened or how to troubleshoot the board?
I have included close-ups of the board front and back as well as the voltage diagram showing the wiring hookup.
I know there are some capable people on here who know at a glance what the problem might be any help would be greatly appreciated.
Attached Images
File Type: jpg Control Board bottom.JPG (1.44 MB, 18 views)
File Type: jpg Control Board top.JPG (1.62 MB, 31 views)
Attached Files
File Type: pdf MC-02 Voltage Diagram.pdf (6.11 MB, 10 views)
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Old 08-19-2018, 02:20 PM   #2
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Default Re: Treadmill DC Circuit no motor start

I would guess the first time you hooked it up on the bench you had a a couple wires mixed up. A close look at U2 looks like it got hot. the `2' in the KA324A looks discolored ands so does the last `1' in the A111B
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Old 08-19-2018, 02:34 PM   #3
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Default Re: Treadmill DC Circuit no motor start

mov1 looks like it could be a soot-sandwich - check it's resistance.
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Old 08-19-2018, 06:57 PM   #4
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Default Re: Treadmill DC Circuit no motor start

Quote:
Originally Posted by R_J View Post
I would guess the first time you hooked it up on the bench you had a a couple wires mixed up. A close look at U2 looks like it got hot. the `2' in the KA324A looks discolored ands so does the last `1' in the A111B
Tks RJ it is possible but not that I recall however how can I determine if U2 is malfunctioning?
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Old 08-19-2018, 07:07 PM   #5
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Default Re: Treadmill DC Circuit no motor start

Easier to just replace. Both U1 and U2 are LM324's equivalents I think...
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Old 08-19-2018, 07:11 PM   #6
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Default Re: Treadmill DC Circuit no motor start

Quote:
Originally Posted by stj View Post
mov1 looks like it could be a soot-sandwich - check it's resistance.
Tks Stj where would one find the spec for that resistor I will check the resistance across it in the morning
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Old 08-19-2018, 08:29 PM   #7
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Default Re: Treadmill DC Circuit no motor start

What voltage do you have between LG3 and LG2, it should vary between 0 and 5 volts when the speed control is turned.
Also check the reed switch wire, that may need to be connected, it receives pulses from the flywheel and may be needed to run.

The mov should be ok, if it was shorted you would know it when you connected the 120v ac. Look at at it closely to make sure its not cracked or split. It should measure open or very high resistance. I see a couple marks on it but thats likely all it is.
The KA324 are quad op amps, digikey has them for under $1.00. I would install sockets for them. something like digikey ae10012-nd or ed3114-nd would be fine.

Last edited by R_J; 08-19-2018 at 09:05 PM..
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Old 08-19-2018, 09:36 PM   #8
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Default Re: Treadmill DC Circuit no motor start

Did you put safety key in place? Is the safety key for activating the micro switch on the control panel?
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Old 08-19-2018, 10:34 PM   #9
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Default Re: Treadmill DC Circuit no motor start

That could be it budm, but the diagram would suggest if the key was not there he would not have 120v a/c across LG4 & LG5.

Last edited by R_J; 08-19-2018 at 10:41 PM..
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Old 08-19-2018, 10:53 PM   #10
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Default Re: Treadmill DC Circuit no motor start

That is what I am thinking too, otherwise he will not have those Voltage on the board, the PDF did not show how the safety key work or how it is connected. The treadmill I use t the gym has magnet puck that activates the reed switch on the control panel if you pull the puck away it will shutdown the machine in case of emergency.
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Old 08-20-2018, 04:13 AM   #11
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Default Re: Treadmill DC Circuit no motor start

Quote:
Originally Posted by budm View Post
That is what I am thinking too, otherwise he will not have those Voltage on the board, the PDF did not show how the safety key work or how it is connected.
The PDF (second page) claims "5VDC will be measured between this terminal (H) and the L terminal whenever the treadmill is plugged in and the safety key is inserted" (emphasis mine) A similar statement qualifies the wiper voltage measurement. ("Low" side, "High" side, "Wiper")

However, the MC02 board seems to source the 5VDC which means the only influence the "console" -- and "safety key" -- could have on the MC-02 would be via gating the mains voltage (by interfering with the "On/Off Microswitch", in some way).

OP could give us a peek at the console's contents to remove any doubt...

The source of the "+12VDC" could also be of interest (i.e., is it just a high impedance source designed as a reference for the SCR firing circuit?)

[I suspect LD1 and LD2 were intended for LeD lamps; LD1 possibly as a power indicator and LD2, perhaps, having a varying intensity wrt speed selected (effectively PWM illuminating with the SCR firing angle).]
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Old 08-20-2018, 05:42 AM   #12
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Default Re: Treadmill DC Circuit no motor start

Both RJ and Curious George are correct the safety key is inserted and functioning. Once it is removed the power is removed. The function of the reed switch in this unit is to read the MPH. The unit will work without it, just no display. Budm the safety key on this unit operates a mechanical on/off switch. Newer unites do have the magnetic type.
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Old 08-20-2018, 05:50 AM   #13
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Default Re: Treadmill DC Circuit no motor start

Quote:
Originally Posted by R_J View Post
What voltage do you have between LG3 and LG2, it should vary between 0 and 5 volts when the speed control is turned.
Also check the reed switch wire, that may need to be connected, it receives pulses from the flywheel and may be needed to run.

The mov should be ok, if it was shorted you would know it when you connected the 120v ac. Look at at it closely to make sure its not cracked or split. It should measure open or very high resistance. I see a couple marks on it but thats likely all it is.
The KA324 are quad op amps, digikey has them for under $1.00. I would install sockets for them. something like digikey ae10012-nd or ed3114-nd would be fine.
RJ the voltage between LG3 & LG2 do vary as the speed control is turned and it is in the 0 - 5 range. The reed switch in this unit only sends a signal to the lcd to record mph/km/h. if it not functioning you just get an incorrect display. I will check out digikey for these IC!! So you are suspecting the KA324's? The MOV is showing OL

Last edited by davg; 08-20-2018 at 07:01 AM..
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Old 08-20-2018, 10:54 AM   #14
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Default Re: Treadmill DC Circuit no motor start

When I look at the ic I see these marks, If the ic got hot due to being shorted internally it can discolor the top.
Does the ic get hot? you could post the voltages of that ic's pins, That may or may not help.
The speed control does seem to connect to that ic so it would have something to due with the speed control, and if it is bad, speed could either be full on or full off depending on how it failed
Attached Images
File Type: jpg KA324A.JPG (109.1 KB, 8 views)
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Old 08-20-2018, 03:09 PM   #15
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Default Re: Treadmill DC Circuit no motor start

Quote:
Originally Posted by R_J View Post
When I look at the ic I see these marks, If the ic got hot due to being shorted internally it can discolor the top.
Does the ic get hot? you could post the voltages of that ic's pins, That may or may not help.
The speed control does seem to connect to that ic so it would have something to due with the speed control, and if it is bad, speed could either be full on or full off depending on how it failed
The IC don't get hot and here are the voltages with one probe on ground starting at the dot (VDC)
Pin 1-54.1,
Pin 2-52.1,
Pin 3-53.8,
Pin 4-42.9,
Pin 5-54.2,
Pin 6-54.2,
pin 7-53.4,
pin 8-54.1,
pin 9-54.1,
pin 10-53.7,
pin 11-54.3,
pin 12-54.0,
pin 13-53.5 and
pin 14-54.0. (Pin 1 and 14 adjacent to each other)
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Old 08-20-2018, 05:22 PM   #16
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Default Re: Treadmill DC Circuit no motor start

You are not using ground to measure the voltages, Use LG3 for your ground or pin 11 of the ic

What point are you using for ground anyway? here is the pdf of the ic
R33 might be open
Check that R33 is not open, the value should be on it, its likely less than 1Ω
Attached Files
File Type: pdf KA324.pdf (388.8 KB, 1 views)

Last edited by R_J; 08-20-2018 at 06:36 PM..
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Old 08-20-2018, 07:34 PM   #17
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Default Re: Treadmill DC Circuit no motor start

beware this looks like a nonisolated possibly capacitive couple PSU, but anyway by superposition,

Pin 1- 0.2, (out1) -- probably okay
Pin 2- 2.2, (in1-)
Pin 3- 0.5, (in1+)
Pin 4- 11.4, (VCC)
Pin 5- 0.1, (in2+)
Pin 6- 0.1, (in2-)
pin 7- 0.9, (out2) -- questionable, may be okay
pin 8- 0.2, (out3) -- this looks overdriven or bad?
pin 9- 0.2, (in3-)
pin 10- 0.6, (in3+)
pin 11- 0, (GND)
pin 12- 0.3, (in4+)
pin 13- 0.8, (in4-)
pin 14- 0.3 (out4) - questionable?

Which of U1 and U2 is this anyway?
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Old 08-20-2018, 08:05 PM   #18
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Default Re: Treadmill DC Circuit no motor start

Quote:
Originally Posted by R_J View Post
You are not using ground to measure the voltages, Use LG3 for your ground or pin 11 of the ic

What point are you using for ground anyway? here is the pdf of the ic
R33 might be open
Check that R33 is not open, the value should be on it, its likely less than 1Ω
Tks R_J Sorry about that but I am a knowledge seeker and have much to learn!! Here are the voltages using LG3 as ground
Pin 1- 0.2,
Pin 2- 1.0,
Pin 3- 0.5,
Pin 4- 11.4,
Pin 5- 0.1,
Pin 6- 0.1,
pin 7- 0.9,
pin 8- 0.2,
pin 9- 0.2,
pin 10- 0.6,
pin 11- 0,
pin 12- 0.3,
pin 13- 0.8,
pin 14- 0.3
R33 is reading .01olms across it unable to see any value on it but for the #10327.
In doing the readings my probe jumpered pins 3 &4 and the motor starts at full speed?
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Old 08-20-2018, 08:56 PM   #19
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Default Re: Treadmill DC Circuit no motor start

I would think the ic is bad, I can't trace where LG2 goes but it must connect to one of the ic input pins, It seems to go under the ic?
check which input pin it goes to, the speed control should vary the input pin and likewise the output pin
when you connected VCC pin4 to pin3 (in1+), out1 told the rest of the circuit to turn the motor full on. So I still think the ic is bad
R33 will be good

Last edited by R_J; 08-20-2018 at 09:00 PM..
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Old 08-21-2018, 08:09 AM   #20
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Default Re: Treadmill DC Circuit no motor start

Quote:
Originally Posted by R_J View Post
I would think the ic is bad, I can't trace where LG2 goes but it must connect to one of the ic input pins, It seems to go under the ic?
check which input pin it goes to, the speed control should vary the input pin and likewise the output pin
when you connected VCC pin4 to pin3 (in1+), out1 told the rest of the circuit to turn the motor full on. So I still think the ic is bad
R33 will be good
I can't see where the trace for LG2 goes under U2 but I buzzed LG2 to the pins on U2 and I get a signal on pin 3 (all wires disconnected).
I did order a couple of the KA324A IC's off Ebay but may have to get them elsewhere if I need them quickly.
I did notice that discoloration on U2 has now disappeared with all the handling? What effect would R5 have on the speed control circuit? looking at the bottom side of the board it do look like some kind of corrosion there? A couple of new pic.
I also just noticed that I reported voltages on U1 in post #18?? The voltages on U2 should read like this using LG3 as ground;
Pin 1- 0.00
Pin 2- 0.06
Pin 3- 0.00
Pin 4- 11.29
Pin 5- 0.02
Pin 6- 1.02
Pin 7- 0.00
Pin 8- 5.21
Pin 9- 5.21
Pin 10-5.20
Pin 11-0.00
Pin 12- 0.00
Pin 13- 0.002
Pin 14- 0.002

Sorry for the mix-up
Attached Images
File Type: jpg 107_7073.JPG (1.67 MB, 7 views)
File Type: jpg 107_7076.JPG (1.55 MB, 4 views)

Last edited by davg; 08-21-2018 at 08:53 AM..
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