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Thorn elliptical cross trainer E3000 - The elliptical cross trainer does not wor

ekler0z 15387 18
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How can I fix a Thorn E3000 elliptical cross trainer whose resistance control motor rotates almost 360° and no longer responds to the computer knob or programs?

The fault is most likely in the load-control potentiometer circuit, especially the big potentiometer on the control panel, because a wrong reading there makes the controller drive the actuator incorrectly; the small potentiometer in the actuator is only for fine cable-tension adjustment [#16748015][#16762451] If the knob has a point where the tension wheel starts acting erratically and everything works again when you move past that point, that strongly indicates a worn or damaged potentiometer [#16762451] One damaged SMD diode on the board (D8) was replaced and the machine worked normally for a few minutes, so that diode or its surrounding parts were also part of the problem [#16755235][#16761083] Since the fault returned, the board likely has another failing component, such as capacitors that have lost capacity or a weak diode in that section [#16761103] The most practical fix is to replace/check the big control potentiometer first, then inspect the board around D8 and the capacitors, or have the control board repaired by someone with electronics experience [#16761103][#16762451]
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  • #1 16741621
    ekler0z
    Level 12  
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    Hello.
    I have THORN e3000 elliptical cross trainer. Recently regulation has broken down. The elliptical cross trainer has its own computer in which programs can be run. I was checking the engine that pulls the magneto-brake cable and works. I checked the power and control cables from the computer and they are OK. It turned out that the control motor after releasing the cord, after connecting the power supply to the elliptical cross trainer, rotates the tensioner by almost 360 degrees and it seems to me that it should at most 45 degrees. Can anyone help me and give me an idea how to fix it? I attach a photo of the computer Thorn elliptical cross trainer E3000 - The elliptical cross trainer does not wor
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  • #2 16741650
    E8600
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    How many cables go to this motor for load regulation? It probably has a built-in encoder that has failed. It's best if you put a photo of this engine.
  • #3 16742686
    ekler0z
    Level 12  
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    To adjust the load goes all the widest tape visible in the photo above. Of this entire tape, only 3 cables supply power and ground to the computer, and 2 cables provide a signal from the wheel rotation sensor. The controller motor is 2 cables and the rest is an encoder, probably three cables. On Monday I will have access to the device and I will send a photo

    Added after 2 [hours] 19 [minutes]:

    The photo was successfully combined
    Thorn elliptical cross trainer E3000 - The elliptical cross trainer does not wor
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  • #4 16747257
    ekler0z
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    I need help again, because this econder turned out to be a B5K rotary potentiometer. Any ideas?
  • #5 16747320
    E8600
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    ekler0z wrote:
    this econder turned out to be a B5K rotary potentiometer

    Check the correctness of the potentiometer's indication with a multimeter if the resistance of the plant increases / decreases linearly. Because he is the potential culprit. The whole system works on the principle of servo.
  • #6 16747814
    ekler0z
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    On the first and second contact the resistance from 0 to 5 kohm is fluid, then from 5 it jumps at 7.6 kohm and so flows to 8.3 kohm and so in a circle that is from 0 to 5 then 7.6 to 8.3
  • #7 16747902
    E8600
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    Should I understand that the potentiometer is without lock rotates around? If so, the indications are ok.

    ekler0z wrote:
    It turned out that the control motor after releasing the cord, after connecting the power supply to the elliptical cross trainer, rotates the tensioner by almost 360 degrees and it seems to me that it should at most 45 degrees.

    Do you normally connect the power supply directly to the engine for a short time? Maybe this is why you conclude that it is too much? Does it put too much resistance on training?
  • #8 16747969
    ekler0z
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    When I plug in the power supply, it will normally turn on the computer and after a while the tensioner wheel will rotate 360 degrees (of course without the cable because it will lock quickly with the cable because the cable tension is only about 2 cm). When the elliptical cross trainer was functional, it was heard that after connecting the power supply the tensioner started to work only when the knob on the computer was turned or a program was started. Currently, the tensioner does not respond at all to the knob or the launch of a specific program. There is also a scale on the string, which in my opinion gives the minimum and maximum deflection
    Thorn elliptical cross trainer E3000 - The elliptical cross trainer does not wor
  • #9 16748015
    E8600
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    ekler0z wrote:
    When the elliptical cross trainer was functional, it was heard that after connecting the power supply the tensioner started to work only when the knob on the computer was turned or a program was started. Currently, the tensioner does not respond at all to the knob or the launch of a specific program.

    You have clarified the situation so you should look for the culprit in the knob on the control panel if it is also on the potentiometer or optocoupler. Alternatively, if not some element could get off in the power path of this control board. First check the potentiometer on the panel is the plate at the bottom of the first photo you posted.

    The driver catches a bug somewhere how it behaves differently than usual, hopefully not a control bone with a charge or processor. The panel displays something when the power is turned on? Reacts to buttons?
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  • #10 16748442
    ekler0z
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    The computer is operating normally, displaying everything to be displayed. The knob is not on the potentiometer and also works because the computer changes when rotating the load (such steps).
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  • #11 16748484
    E8600
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    Have you checked this potentiometer? Perhaps he is responsible for preload? Maybe it is damaged or disrupted? There is no sensor with this potentiometer.

    Thorn elliptical cross trainer E3000 - The elliptical cross trainer does not wor

    Which potentiometer did you check before because I meant the big one.

    Thorn elliptical cross trainer E3000 - The elliptical cross trainer does not wor
  • #12 16748684
    ekler0z
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    I checked the big one and the little one. The parameters I wrote about above are from this big one.
  • #13 16755235
    ekler0z
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    While checking the computer board, I noticed that the D8 diode is chipped. Multimeter measurements show nothing in both directions. It seems to me that all the LEDs next to D8 were the same. On the others, the multimeter measurement in the diode checking mode gives a result of 560, while in the ohm measurement mode it gives a result of about 1200 k. What diode could I solder in place of the damaged one?
  • #14 16755800
    E8600
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    What a colleague has measured does not say much (it only says that it is a silicon diode - 0.6V voltage drop), please upload an accurate photo of this diode, someone can recognize. If it has any symbols, try to read. It can be a diac, zener diode or other invention.

    Here on page 3 you have the LEDs designation based on the colors of the stripes (mask code).
  • #15 16756154
    ekler0z
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    No markings visible
    Thorn elliptical cross trainer E3000 - The elliptical cross trainer does not wor
  • #16 16756354
    E8600
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    It looks like a regular switching diode LL4148 but let somebody else speak because I am not a specialist in SMD.
  • #17 16761083
    ekler0z
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    I replaced the diode with a new one and the equipment began to work as it should, i.e. I could freely control the tension wheel using a computer but after a few minutes the problem returned again. I checked the diode and it's ok.
    I am slowly starting to think about firing the control computer and replacing it with a 6-pin rocker switch so that I can control the pull wheel back and forth. I would also have to reduce the voltage with some stabilizer from 9v to 5v because without it the engine works too fast
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    #18 16761103
    E8600
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    ekler0z wrote:
    I replaced the diode with a new one and the equipment began to work as it should, i.e. I could freely control the tension wheel using a computer but after a few minutes the problem returned again.

    Apparently not only the diode went down. I would check the capacitors probably lost capacity. Did you check if this new diode got a break or break? If you have any trusted electronics, entrust it with repair. Some element in the line of this diode probably fell.

    It is not excluded that this new diode was too weak so it is in those Chinese inventions where there are no element markings. Conquer the topic or create a new one: "Identification of the SMD diode" maybe someone had something similar to do and suggest the right one.
  • #19 16762451
    ekler0z
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    Another breakthrough in solving my problem. A small potentiometer in the actuator is used for precise adjustment of the cable tension and if I set it to the appropriate value then after connecting the power supply the tension wheel after 360 degrees rotation apparently sets in such a position that it starts to operate normally. Today I will fly to the store for a potentiometer (the big one) because probably like a colleague a few posts above suspected, it is damaged. There is a moment in adjusting the computer knob that the tension wheel begins to go crazy in such a way that e.g. it turns in the wrong direction and if the knob "jump this point" then everything is ok. I suspect that at this point the tensioner wheel normally stopped and after reading incorrect potentiometer values - the computer was stupid.
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Topic summary

✨ The discussion revolves around a malfunctioning THORN E3000 elliptical cross trainer, specifically issues with the load regulation system. The user reports that the control motor rotates excessively (nearly 360 degrees) instead of the expected 45 degrees. Various components, including the potentiometer and encoder, are examined for faults. A damaged diode (D8) on the control board is identified, and after replacement, the system initially functions correctly but later fails again. The user suspects that a small potentiometer in the actuator may be causing erratic behavior, leading to incorrect tension wheel operation. Suggestions include checking the potentiometer's functionality and considering the replacement of other components like capacitors. The user plans to replace the large potentiometer to resolve the issue.
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FAQ

TL;DR: Suspect feedback and protection parts first: a “silicon diode – 0.6 V drop” and a worn B5K position pot commonly cause erratic load control on the Thorn E3000. "Silicon diode – 0.6 V drop." [Elektroda, E8600, post #16755800]

Why it matters: This FAQ helps home techs quickly restore proper braking control without replacing the whole console.

Quick Facts

Why does my Thorn E3000 tensioner spin 360° when I plug it in?

That behavior means the load actuator loses position feedback, so the controller “hunts” the full range at start. Typical culprits are the big B5K potentiometer’s dead spot or a failed D8 protection/drive diode. The console may still boot and show data, yet the actuator ignores knob commands. Verify cable travel is limited (~2 cm) before testing to avoid mechanical jamming. [Elektroda, ekler0z, post #16747969]

How do I test the big B5K potentiometer correctly with a multimeter?

Disconnect one side of the pot. Measure resistance between the wiper and an end pin while turning slowly. You want a smooth sweep. A jump from 5 kΩ to about 7.6–8.3 kΩ indicates wear and will confuse the controller, causing direction flips or runaway motion. Replace if you see any discontinuity. [Elektroda, ekler0z, post #16747814]

What does the small potentiometer inside the actuator do?

It is a fine‑tune trimmer that sets baseline cable tension. Set it so the cable rests within the printed min–max scale. With a good setting, the wheel may rotate once on power‑up, then the system accepts knob and program commands normally. If mis‑set, the unit can hunt or stall. [Elektroda, ekler0z, post #16762451]

The console turns on, but the tensioner ignores the knob—what should I check?

Check the panel input circuitry first. Inspect the knob’s sensor interface and the control board power path for any disturbed or failed parts. A faulty input path or missing supply rail can make the driver “think” it’s in error and refuse to move on commands. "The driver catches a bug somewhere." [Elektroda, E8600, post #16748015]

I found a chipped D8 diode. What is it and what can I replace it with?

D8 looks like a small SMD switching diode used in the actuator drive/protection path. Community identification matches LL4148‑class parts. Replace like‑for‑like, observing polarity. After replacement, re‑test actuator response and confirm no shorts on the motor lines. [Elektroda, E8600, post #16756354]

Replacing D8 fixed it for a few minutes. What’s the next suspect?

Intermittent return of the fault suggests additional stressed components. Check electrolytic capacitors in the same drive/control path and confirm the new diode’s rating suits surge conditions. Aging caps can drop supply stability, making control erratic after warm‑up. "Apparently not only the diode went down." [Elektroda, E8600, post #16761103]

Can I bypass the control board with a rocker switch to move the actuator?

Yes, users have considered a 6‑pin rocker to drive the actuator motor back/forward and reducing motor voltage from 9 V to 5 V to slow travel. This is a last‑resort workaround and removes program control and safety interlocks. Add a fuse and limit stops if you attempt it. [Elektroda, ekler0z, post #16761083]

What does “servo” mean in this elliptical’s load system?

The load mechanism is a simple servo: the controller drives a motor while reading position feedback from a potentiometer until the target tension is reached. As one expert put it, “The whole system works on the principle of servo.” If feedback is noisy, motion becomes unstable. [Elektroda, E8600, post #16747320]

How much cable travel is safe during tests?

Expect roughly 2 cm of useful travel at the magneto‑brake cable. Exceeding this risks binding or snapping the cable. If you test with the cable disconnected, watch for a full 360° motor rotation at startup, which signals lost feedback. Reconnect only after fixing feedback. [Elektroda, ekler0z, post #16747969]

The actuator reverses mid‑adjustment or moves the wrong way—what causes that?

A worn spot on the big potentiometer can feed incorrect position to the controller. When the knob passes that point, the system may command the wrong direction or oscillate. Replacing the pot and setting the small trimmer usually restores correct behavior. [Elektroda, ekler0z, post #16762451]

How do I recalibrate baseline tension after replacing parts?

Try this quick procedure:
  1. Set the actuator’s small trimmer so the cable sits mid‑scale at rest.
  2. Power on; let the wheel complete its initial rotation and settle.
  3. Verify the console knob steps change load smoothly end‑to‑end; tweak the trimmer slightly if the start or end sticks. [Elektroda, ekler0z, post #16762451]

What resistance should I see across the large position potentiometer?

It is a B5K device, so expect about 5 kΩ end‑to‑end. During rotation, wiper‑to‑end should change smoothly. A jump into the 7.6–8.3 kΩ region shows failure. Replace the pot to restore stable control. [Elektroda, ekler0z, post #16747814]

How can I tell if a suspect diode is silicon using my meter?

Use diode‑test mode. A typical reading near 0.6 V indicates a silicon switching diode in the forward direction. Reverse reading should be open on a good part. If the package is damaged or readings are erratic, replace it and re‑check the surrounding path. [Elektroda, E8600, post #16755800]
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