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Treadmill Controller Board

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earl42

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Forgive my "electronic idiocy," it's been well over a decade since my last electronic course!

I have a Bowflex Series 3 Treadmill that stopped turning the "tread" recently. I have talked with Bowflex support which, while very courteous, was obviously reading from a script.

They had me test continuity for wiring going from the controller board to the interface and whether certain leds would light while running. Then she said the motor needed to be replaced and thankfully that was under 10 year warranty so I was shipped a new motor, which I received and installed, but the problem remained.

Since seemingly everything other than the tread drive motor works (interface lights, buttons work, incline motor works) I'm thinking that it either has to be the motor or the controller board. And since the motor was replaced, that only leaves the controller board. The electronics only carried a 2 year warranty which has expired, and this controller board runs about $300 dollars which I sadly cannot afford.

The controller board is a "Bowflex Treadmill Controller 18505", and can be found online by searching for that phrase in quotes. (Sorry, I can't post links yet because I'm new.)

This particular treadmill uses a 90v 15a 1.75hp 4600rpm motor. (Turdan Industry Co. Ltd. catalog listing B2K051)

What is weird is that I have used a DMM to test the voltage supplied to the motor, and at all times I am reading about 19 volts. Whether the tread should be spinning or not, I get 19 volts. I'm sorry if this is a stupid question, but shouldn't I be getting around 90 volts to drive the motor?

Thank you very much for reading and for any assistance you could provide!
 
I've reworked several treadmills, they've all been PWM to the belt. Your DMM is useless on a PWM signal (see aliasing...). It takes an o'scope.

The 2 year warranty on the power block is easy: 1st point of failure. I be tickled at a "free" 1.75 HP DC motor, but you're still saddled with the problem: power block probably bad.

Two paths: pony up $300 or a Serious Tour in PWM / mosfet drive tech. Door #1 fixes the unit. Door #2 results in a simple fast/slow belt, that's IF you're comfy building it. Good Hunting... <<<)))

P.S. This Was on a surge suppressor?? Most don't know that bad power can play Hob with PWM blocks.
 
Yes sir, it was on a surge suppressor, and I would usually not even leave it plugged in when I wasn't using it because I knew I couldn't afford another one. :)

Since I don't have the schematic for the controller board (and I have searched), do you think it would be possible to find which component(s) needs replacing? I know most people wouldn't bother, but I really can't buy another and I am definitely willing to spend some time on this.

Otherwise, would building a PWM / mosfet drive as you suggest mean that I would control the treadmill without using the original interface? Or is it something that just is added to or with the existing circuitry?
 
Most DMM's will read very high at very low speeds where the actual RMS voltage is really pretty low. A few high end DMM's, like a Fluke 189 and such, will make some sense out of the PWM signal but most will not. It's the frequency involved along with the brushes and the inductance in the motor. I suspect the 19 Volt measurment means the controller is unable to charge the bus capacitors or is doing a Power On Self Test with partially charged bus capacitors and finding some signal that indicates an SCR, MOSFET, or IGBT is blown. The actual RMS voltage is probably less than a volt or so and not enough to actually spin the motor. If the controller goes ahead and tries to fully charge the bus with a blown output device, the PMDC motor will be demagnetized by the sudden 100 Amp-ish current spike.

I would check and replace suspect power semiconductors. From my experience, tracing signals back from there to the gate drivers on a modern treadmill motor controller can be done but anything more is pointless. It not only takes forever but you'll soon find yourself staring at a microcontroller with no way to program it.

I don't remember what signals Bowflex uses to send commands to its controllers. A couple of manufacturers use RS-485 which would allow you to sniff out some commands but then you're stuck figuring out what checksum they're using and then what each command supposed to do. A couple of other manufacturers use signals are much easier to make sense of. In either case, building a PWM drive most likely means abandoning the current control console in favor of something homebrew that's relatively easy to implement.
 
Cachehikers' got it right: You can try replacing the power components, but anything else virtually Requires the schematic (BTDT). The homebrew is a totally separate approach, replacing all existing belt drive circuitry. Once built/proofed, it's a simple fast/slow control, but if it goes south, you can fix it. G.H. <<<)))
 
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