Diagnosing a Jazfit Treadmill Power Control Board

Thread Starter

pokethebear

Joined Nov 25, 2010
57
Thanks for the feedback jatinah. It's 240VAC here, Australia.

I don't know enough about what's driving the opto yet to be able to tell exactly where its signal is coming from, but that will come in time as I work back through the circuit.

Motor checks are all good, and as mentioned earlier it drives the belt fine using an external DC supply. Cable to console looks fine too, although I haven't yet tested every pin for continuity.

On that note, I think I'll do that next - at the console board. One thing I didn't mention is that this fault happened right after the previous owner moved house. It apparently wasn't dropped or anything like that.

I was actually just getting ready to post here asking if anyone could think of a reason why moving the machine could cause this ... and now I'm wondering about that cable. It's disconnected at the top end whenever the machine is disassembled. Any other suggestions along that line of thinking are welcome.

If that turns out to be the fault, then at least I've learned more about DC motor control :D
 

Thread Starter

pokethebear

Joined Nov 25, 2010
57
Cable tests good. Had it been the problem, it would have been funny and a great lesson in troubleshooting.

In the process though, I found an excellent way to mount a cover to a piece of tubing AND run a cable through it at the same time! Who would have thought of this design, in a machine prone to vibration? Top notch engineering!

(I never expected much of this machine btw, it was built by an invisible μcompany. I'm just having a laugh and learning something along the way)

Edit: I say I'm having a laugh, but at the same time I really do appreciate the help here.
 

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debe

Joined Sep 21, 2010
1,389
Dont quite know what Q2 / S6025L does but in the picture the center pin apears to have a dry joint needs re soldering.
 

R!f@@

Joined Apr 2, 2009
9,918
U need to reflow solder on top to the board or apply enough so the solder flows to the top side.

Next, a triac is never used in regulating B+, always an SCR is used. The B+ will be adjusted to minimize driver power dissipation. It will vary from around 100V to 200VDC.

Does the LED's on the board light up when you power up the tread?

Does the console lights up normally?

What does the LED's state, the writing on the board near the LED?

Does the Auxiliary transformer supplies the stated voltages and does the respective rectifiers produce the auxiliary DC voltages?

First post these answers.
U have to reconnect the board and measure the DC voltages asked above.

And so be careful. Have somebody to hold the board.

And if everything checks out, show me the tacho/speed sensor. If you can check it too. it could be a problem.
 

Thread Starter

pokethebear

Joined Nov 25, 2010
57
tom66 said:
Check D4 using the diode check function of your meter.
D4 checks fine using diode test.

debe said:
Dont quite know what Q2 / S6025L does but in the picture the center pin apears to have a dry joint needs re soldering.
You're right, I will resolder and test again.

R!f@@ said:
Does the LED's on the board light up when you power up the tread?
The one near the filter cap (LED1) lights up looking like half brightness, when I press the start button. Check the schematic: that one only shows DC across the filter cap. The other two LEDs are for the incline motor up/down, and they work fine.

R!f@@ said:
Does the console lights up normally?
Yes, the console works fine as far as I can tell. It displays timer, controls the incline, displays speed selections, everything. The magnetic safety switch works perfectly as well.

R!f@@ said:
What does the LED's state, the writing on the board near the LED?
LED1. That is all.

R!f@@ said:
Does the Auxiliary transformer supplies the stated voltages and does the respective rectifiers produce the auxiliary DC voltages?
That Tx doesn't have any stated voltages on it. Measured output is as noted on my last attached photo. I haven't yet tested the DC voltages from its rectifiers - that's next.

R!f@@ said:
show me the tacho/speed sensor. If you can check it too. it could be a problem.
That is a very simple binary circuit that only tells the brain whether the belt is turning or not. It's one magnet on the motor pulley triggering a magnetic sensor. It works fine ... if I keep manually moving the belt while the machine is powered up and start button is pressed, there are no errors. When I stop manually moving the belt, an error appears as expected. It's a cheap "yes or no" thing that just checks whether belt movement is happening or not.

-------------------

I still want to find out why there is no (little) DC voltage across the filter cap. When I get time next, I will manually drive the opto TLP561G output, then work my way backwards through that circuit.
 

R!f@@

Joined Apr 2, 2009
9,918
Hmmm... So you need to check the auxiliary voltage first.

My first guess is that the B+ driver stage is faulty or a faulty protection stage.
 

Thread Starter

pokethebear

Joined Nov 25, 2010
57
Edit: I posted some tests that skipped ahead of the best troubleshooting process. Original post left to show what NOT to do without verifying the entire rest of the circuit:

--------------

Progress.

I shorted the output of the TLP561G optoisolator at pins 4 and 6. Treadmill runs. Speed control works as well. Slow speed, medium speed, fast speed, incline, it all appears to work fine.

I haven't tested the opto itself out of circuit yet, but I have measured its input when the board is powered ... the voltage across the input pins 1 and 2 is a steady ~0.7VDC.
 
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Thread Starter

pokethebear

Joined Nov 25, 2010
57
Opto tests good, as does D8. C14 isn't shorted.

That's all I have on the schematic so far, so I'll be tracing that circuit further and adding to the schematic as soon as I can.
 

R!f@@

Joined Apr 2, 2009
9,918
U are doing what u think is right.
Trial & error...I am sorry I cannot guide u tht way.

I told u to check the auxiliary DC voltages. It's obvious your B+ driver side is not working.

You will be lucky if you can get it fixed shorting out what you dunno. I surprised that nothing blew when you turned on the SCR fully . You will definitely get 300VDC. If that cap was under rated it would have blown up on your face.

It is this kind of actions that get threads locked
 

Thread Starter

pokethebear

Joined Nov 25, 2010
57
R!f@@, out of respect for your help and for the learning that this forum can give to other users, I will avoid posting seemingly random actions like that without completely explaining the reasons for my actions.

Out of respect for your help and the desire for you to continue helping, I will wait for, follow and answer your instructions as requested before progressing further. I'm not in a hurry, I have plenty of other things keeping me busy in the meantime.

Your main point is completely valid. However, I need to clarify a few things:

R!f@@ said:
Trial & error...
R!f@@ said:
shorting out what you dunno
Absolutely not trial and error, and not just "shorting out what I dunno". I realize that given what I've said it may very much seem like that, so I need to clarify. I know exactly what the output of that opto does, and what parts of the circuit it affects. My test confirmed the operation of much of the related circuits, and removed all of those parts from the troubleshooting equation.

I had not at that time explained what other components I had tested, and for that, your main point is valid.

R!f@@ said:
I told u to check the auxiliary DC voltages.
I did. I had not posted those results here, and for that, your main point is valid.

R!f@@ said:
It's obvious your B+ driver side is not working.
Yes, obvious.

R!f@@ said:
I surprised that nothing blew when you turned on the SCR fully .
I'm not. At all. I have tested more than what is currently shown in the schematic, and nothing is in a condition to cause a blowout. Once again, I did not advise that in this thread. My apologies, it's the wrong way to communicate with someone who's helping from a distance, and the wrong way to post in a thread that others might learn from.

R!f@@ said:
You will definitely get 300VDC. If that cap was under rated it would have blown up on your face.
As mentioned, the cap is new. Obviously, new components can be faulty ... but the thing is, if the new cap was going to blow at the expected 300V, then it or something else would have blown up on my face anyway when I eventually fixed the original fault. The expected voltage is clearly 300V, the cap is rated at 400V, and if it's under rated it will fail no matter what. When I simulated the opto switching on, the same thing would have happened.

R!f@@ said:
It is this kind of actions that get threads locked
That doesn't surprise me. I imagine many people of many different experience levels learn things from this forum.

I have been working so far from a side-by-side standpoint, but I understand that the help given here may be given from the instructional standpoint. I'm happy to sit back and just follow instructions like anyone who's gone through the apprenticeship. It doesn't bother me to do it again.

Instructions?
 

thatoneguy

Joined Feb 19, 2009
6,359
I think that board is fine, since your unique method of testing the opto showed all functions normally.

We need to find what is stopping the "go" signal from reaching the opto isolator. A safety switch somewhere that got bumped? Wire not fully connected in a jack, stuff like that maybe?

I can't tell where the inputs to the optoisolator are, the bottom side has the white block over the traces where I think the opto is soldered in on the bottom side.
 

Thread Starter

pokethebear

Joined Nov 25, 2010
57
Yeah thatoneguy, I thoroughly checked for anything that may have been bumped, everything in the whole machine. Connectors, safety switch, circuit breaker, it all checks out. It is odd that it stopped working right after being moved, but I didn't find anything that could obviously be caused by that. Every line in the harness from the console board to the power board tests fine as well.

I'm following the circuit back from the opto as I get time. The inputs to it, under the resistor on the back of the board, are shown on the schematic (as far back as I've traced the circuit so far).

Perhaps the enable signal is supposed to be sent from the console board and the console board isn't sending it? I wouldn't mind knowing which pin, if any, on the harness connector supplies the enable signal, because that could eliminate the entire motor control board. But, that would be jumping the gun and qualify as a unique method of testing, so I'll finish drawing the circuit first and wait for that information to come with time.

There are some new random components on the schematic now; I haven't traced all of the connections to them yet. The schematic is a work in progress that hopefully will be updated soon.
 

thatoneguy

Joined Feb 19, 2009
6,359
Y
Perhaps the enable signal is supposed to be sent from the console board and the console board isn't sending it?
This is what I am thinking. Is the wide connector the one that goes to the console/control/display board? It may have a few lines out from there that need to be OKbefore it turns on the opto. These would be items like cover is on, or something odd like "machine is not laying on it's side".
 

Thread Starter

pokethebear

Joined Nov 25, 2010
57
thatoneguy said:
Is the wide connector the one that goes to the console/control/display board?
Yes. I attached a labeled photo a few posts back. Although, disregard the smaller connector in the same area; it goes to the incline motor rather than the console board.

I didn't find any cover/tilt/etc. switches or sensors anywhere, although I may have missed an inconspicuous looking tilt switch. The usual safety switch on the console works fine.

Hopefully I can get through more of the power control board circuit today.
 
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