Fixing a broken treadmill – Nero Sport HU143NG Foldable Treadmill

Yeah I like tinkering in the garage and hoping this may well help someone in future.

Picked up a faulty treadmill (again) from someone local and figured I could have a tinker after the success of fixing my first one.

It’s a Nero Sport model HU143NG but as with a lot of treadmills they seem to a generic model and available under various brands.

Fault – dead. As disco. That was all I was knew.

Step 1 – Basic Check

Plugged it in and turned it on. The power switch lit up so it wasn’t something simple like the plug top fuse. It was getting power  to switch at least.

The control panel was dead, no obvious physical issue like a smashed screen but nothing on it, no display, no response to buttons etc.

Step 2 – Check Control Panel

Common faults can be the cable between control board and the main circuit board. Especially on folding units these can wear over time.

On this unit the display was wobbly and appeared to be missing the bolts to stop it rotating on the metal frame so could just rotate around and around until cable or screen breaks.

I took the rear panel off the control panel -lots of little screws.

First issue was pretty clear. The black cable with the white plug that connects to the circuit board was not connected.

Looks like the control panel has twisted around the frame enough times to pull out the cable.

Step 3 – Reconnect Control Panel and Test

Released the circuit board and adjusted the slightly pulled cable coupler socket and reconnected

Turned back on and screen powered up. Success!

It beeped constantly and displayed an Error. Bum.

This is where lack of attention wasted me time on the next few steps. Skip straight to step 7 if you want to save time!

Step 4 – Check Main Power Board

Couldn’t find anything on internet on the error codes. Some treadmills give useful codes identifying motor issue, speed sensor issue etc. This just said Error. So next thing to check was the main power board.

Took the cover off the motor housing. Standard arrangement of a big DC (direct current) motor and a main power board. This converts the AC mains power to DC for the motor among other things.

Main power board looked all OK, no signs of overheating, blown components etc. Most boards will have some large capacitors on that can hold charge even with power off. Don’t poke around like an idiot.

It did have a fair bit of hot glue applied to components on the board. It was unclear if this was done at factory or by previous owner in a repair. Given it was on other components on the treadmill I think it’s original.

It did have a separate fuse mounted on the board. I pulled this off and checked for continuity (is there a circuit through the fuse?) it was OK and hadn’t blown so pushed back in.

Not much else to check on board without a lot more effort or test gear.

Step 5 – Test Motor

The motor is direct current (DC) not alternating current (AC) like the mains so you can’t just connect 240V from the plug to it as you’ll fry it, start a fire and get told off for being an idiot and messing with electricity.

Instead I disconnected the motor from the power board by unplugging the positive (+) and negative (-) leads. Make a note of which is plugged into where if not clear. In this case the terminals were marker + and -.

You can use a small battery or a low voltage DC power supply to test the motor.

I used a 12V car battery charger, connected the crocodile clips to the terminals (all while off), red to red, black to black. If you get this the wrong way around it will just run backwards at this stage, no issue as you’re not running on the treadmill.

Turned on battery charger and the motor spun well, no noises, no burning smells etc. At very least I had a working motor to sell for spares.

Step 6 – Test Cable to Control Panel

Bum. The cable that connects to the screen from the power board is glued into it’s socket on the power board so couldn’t easily disconnect and check the continuity in the cable to determine if breaks in cable. Given the control panel was powered up and beeping it was fairly likely it was OK but would have been good to check. It’s a three core cable so without knowing detail of the wiring I presume it positive and negative power (+/-) and a signal cable of some sort so a break of just the signal could have a functioning board and errors potentially.

Step 7 – Stop Being Stupid – Safety Switch

When I first gave the unit a look over I noted it didn’t appear to have a safety key function. It didn’t come with a magnetic safety key and there wasn’t a separate board containing a reed switch (a switch that is closed in presence of magnet) as I was expecting. So I presumed it didn’t have a safety kill switch being a cheaper unit.

Then I looked closer at the control board and saw a tiny reed switch on the unit itself. Idiot.

Using a fridge magnet to close the switch I turned the treadmill on again. It worked. Error message gone, now just OFF, awaiting a start.

Step 8 – Put It All Back Together

Reassembled everything, put covers back on, all fine.

Step 9 – Kick Yourself

So the only things wrong with the unit were a twisted control panel section had pulled the cable out, and the magnetic safety switch was missing. I could have done skipped steps 4-6 if I’d bothered to realise all treadmills need a safety switch.

Step 10 -Tidy Up

Few bolts were loose or missing, so sorted them.

Installed some bolts and washers to keep the display in place for future and prevent a repeat of the issue.

Tensioned the belt. Looks like someone has fitted a slightly narrower belt at some point. Works fine but could do with being an inch wider.

For now using a fridge magnet but really needs a proper magnetic key, these are on eBay and Amazon for a few quid.

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