Hi, new member trying to repair a Jazfit T45 treadmill that I picked up for free. I am somewhat experienced at troubleshooting and repairing some electronics, but nowhere near being an engineer. Thanks to anyone who can help.

Fault description: no belt movement. When the start button for belt movement is pressed, the relay on the power control board clicks. Manually moving the belt at this time doesn't help it get going. The belt moves freely manually, and the motor runs the belt fine using an external DC source. Control console and motorized incline both work fine.

Output to motor reads ~3VDC when the start button is pressed. The LED near the large capacitor glows at around half brightness whenever the main power is turned on.

I haven't been able to locate the manufacturer, and a replacement board seems to be unavailable. Schematic is also unavailable, but I will draw one out from the board if I have to.

Aside from replacing the large capacitor, I've targeted the output components first ... advice is welcome though if other components are known to cause problems.

Referring to the pictures below, my biggest problem is identifying and sourcing some of the components attached to the heat sink (edit: the middle one was unsoldered in the picture if you're wondering). The one on the left shouldn't be too hard; information seemed fairly easy to find for it, but comments about it are of course welcome.

I ~think~ the G80N60 in the middle is the same as this. If so, then I have a source for that one. If there might be issues, please let me know. The one in the link is an IGBT, which I don't believe I have the tools to test, but it's only $11 so I'm willing to spend that anyway.

The last one on the right is the sticky one. Nobody here in Australia seems to be able to reference it. The datasheets here seem to match(?) but I don't know how to find any equivalents, other than perusing data sheets for compatible specs. If that's what I need to do then I might have to do it, but does anyone here have any better ideas?

Thanks again for any help. I'll aim to stick around and offer the community any help I can after this.

 

Hey Welcome
If you can draw it up...helps a lot.

From the picture I see an opto, which I believe drive the B+ control.

First you need to test the power components. The bridge and the fuses. If not sure, remove them from the PCB and test it and post the results.

You can get parts from mouser or digikey, it is where I buy parts for treads that I repair

 

Thanks for the quick reply and the mouser and digikey names, R!f@@.

I'll work on drawing it up, but that will take some time since I haven't drawn up a board in years and I'm sure I've forgotten half of the components I also have to fit it around work over the next few days.

The fuse is good; I forgot to mention that I had tested it. Locating the opto driving the B+ control is a bit above my expertise; I can ID and test many components, but not all. I'm working on it

I hadn't tested the bridges (there are two); the relay clicking led me to assume that they were ok, which was a silly oversight. I'll pull them out and test within the next hour and post results.

 

Not the bridge..I mean if U can measure RAW DC which is 300VDC across the filter cap once powered bridge is OK.. U need to be sure about the MOSFET, the Protection diode and the SCR that regulates B+, these are the commonly referred power components

Take your time, I am usually around, besides there a lot of members here that are quite capable of getting u to fix it, if you keep at it.

Like I said a good schema will let us tell u exactly what to look for

{ed}
It's a good thing you posted with pics first. Pictures always helps a lot.

 

I tested the bigger bridge rectifier out of circuit before I refreshed the page anyway. It doesn't test like it should ... although I'm a bit puzzled. Either my meter is playing up, or I've forgotten something basic about medium-duty bridges. Or, I'm just going batty and I'm currently a resident of Shutter Island.

In one direction, all 6 tests (4 pins) show infinity as expected. In the other direction, 2 show infinity and 4 show: 16kΩ on the 20k scale, 78k on the 200k scale and 426k on the 2000k scale. Meter is functioning normally on all other tests ...

This is potentially embarrassing if I should know this, but I can take it.

PS: yes, fingers are off the probes

PPS: I'll have to solder some wires to the cap pins for a powered test .. the whole back of PCB is about 1cm away from the heat sink.

 

Disregard, forgetting that diode mode is required when testing. Toldya it would be potentially embarrassing It's been a while, and I can see that half of this exercise is going to be re-learning some of the basics. Which, I suppose, is better than not learning at all.

Will check the hot voltage across the cap shortly.

 

Silly time over. Voltage across the cap is measuring 9VDC. By the way, I mentioned soldering test leads because space on the front is quite tight as well. I didn't think I'd have room to get at the test points on the front, but I do, just.

 

What are you using for a meter?

Does it have a Diode test function and a cap test function?

 

Show me how the connections are and the type of meter you use.

Photo.....show me photos

 

What are you using for a meter?

El cheapo basic digital. It has diode test, which I used for the bridge. That looks ok. No cap test, unfortunately.

A ~very~ partial schematic is here. I'll keep updating that file as I get more done, unless people prefer I attach each version to a separate post. As I mentioned, progress will be slow. I put it up in its current state just in case anyone gets any suggestions from it. Now that I've started making it, I can see some more tests to do anyway.

I only have the default Tinycad libraries, so I'm missing some components while I try to find more libraries. Of note are the G80N60 and F30U60DN; I don't have the symbols shown in the datasheets. Wouldn't mind a generic IC symbol either ...

R24 is a high wattage resistor mounted on the underside of the board, and C21, C22 and C23 look like diodes with no stripe, but they're labeled with C. You can see them in the closeup output.jpg in my original post.

 

Show me how the connections are and the type of meter you use

Not sure what you mean by how the connections are. The meter probes are just the basic pointy ones. Very limited by budget for a better meter purchase. I do need some clips, I'm going to see about at least picking some of those up anyway. If you want a photo of the meter, I can take one in a couple of hours when the camera is back at home ...

 

How are you measuring the voltage with mains connected.
I like to see the tread. with the wires connected to the board

 

One with assembly loose, one bolted in.

Edit: no, I don't apply power with the assembly loose, especially with the motor connected

 

That thing is tiny..u shud look at my threads..

Ok. so now find out and mark the connections on the board photo, so we can understand which jack goes where.
From what I see, you have a step down Tx.

Mark the connections on a posted photo. This way I can tell you what to do, since you did not find any shorted components or open fuse. I suspect a resistor value gone high or a leaky electrolyte.

you might need to give power to the board separately. Since you are tackling the job prior to our knowledge I assume you are familiar with mains voltage related dangers.

 

It is tiny, cheap manufacturing getting away with as little as possible I guess. I got it for the right price (free), so it's kind of just a project for me, and I do need a treadmill anyway so it's a bonus if I get it fixed.

Some of the board connections are on the schematic, if that helps, but I'll mark the photo shortly.

I'll definitely power this up on the bench now, and probably start working back from the thyristor as I finish the schematic. Mains voltage safety is not an issue at all. Back in the dark ages when I was a tech, the other guys would laugh at my OCD methodical safety checks, and I'm the same now .. I've always taken safety seriously.

Update soon.

 

I don't think the main filter cap would be faulty, but to test it with only an ohmmeter is quite simple. Just set your meter on the highest ohms scale, then attach the leads to the capacitor. The reading should slowly climb up over a period of about a minute. If it stops anywhere less than about 1 Mohm I'd be concerned.

 

It appears the solder missing on the top of the PC board for the middle device's pins.

The bottom side of the board in that area doesn't look so good either, grey rather than shiny.

That device could have gotten hot enough to melt the solder away, or was it removed and put back onto the board?

 

That device could have gotten hot enough to melt the solder away, or was it removed and put back onto the board?

I think that it's just a shoddy soldering job from the manufacturer. I've seen similar stuff on power transistors. The transistors aren't usually added by machine; it's just not worth it to have a custom machine for a few components like that (odd shape for pick 'n' place) - they are often added by hand, and sometimes even hand soldered. I don't think the device could have got hot enough to melt the solder on its exposed leads; the die would have to be hot enough to melt the plastic casing before this happened.

 

R!f@@, here's the photo with labels.

It appears the solder missing on the top of the PC board for the middle device's pins.

Good pick, and my apologies. I had removed that for testing and hadn't soldered it back in yet. I had meant to mention it in my original post but forgot. My bad.

I don't think the main filter cap would be faulty, but to test it with only an ohmmeter is quite simple.

The cap is new, and I ohmmeter tested it anyway cause I'm OCD But thanks for the info. On that note, thanks to everyone helping.

I would think that not having full voltage across the filter cap should be caused by either the thyristor / SCR, something driving it (R14, D2, opto, or further back along that path), or the relay contacts (which would be odd?).

That wouldn't necessarily be the entire problem of course, but that's where I'm looking today.

 

Hi...I looked at your drawing and it is quite good. You are right, the opto controls the triac which allows the DC Filter cap to charge, as well as energizes the motor power rail. This is "after" the relay energizes to supply ac voltage to the bridge rectifier. The filter cap should see less than 200vdc if this unit is a 115vac model(about 165vdc-careful!), not +300vdc as told earlier.
When you press the "Start" button, you said you hear a "click". This click should be the main power relay you have in your drawing.
The daughter-board should sense this DC level and allow the triac to fire, via the opto, which may be controlled by the daughter board as well?
If the triac is allowed to fire(far left Teccor part), the Main motor DC power rail will energize, and will be ready for the switching FET (part on the left of your photo)(the dual diode is your kickback diode for the motor current, on the right). The 30U60 is 600v(prv) 30A(cont.forward-I).
If the Triac doesn't turn on, the large filter cap won't charge to much. The triac will not turn on if there is a shorted motor(check for a few ohms across the windings, maybe a few hundred ohms or less, but not very very low), an open motor, or a low DC rectified voltage, or the safety key is missing, or a few other possibilities. The upper console may also supply an "Enable" signal to the motor control board. Does the cable look ok going from the upper to lower board?