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Treadmill Controller Varistor blown

Discussion in 'Troubleshooting and Repair' started by Krishnasastry, Sep 25, 2019.

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  1. Krishnasastry

    Krishnasastry

    4
    0
    Sep 25, 2019
    HI
    I had purchased a TreadMill having a the control board TD-700 V1.2. While my son
    was using, the varistor (top left, green shaded) blew-up. Although I replaced the same
    but the machine is not starting (not even the relay engaging).

    Components replaced:
    After this I suspected some component burns (not visible to naked eye)., I replaced
    the fast rectifier FEP30JP and the Toshiba GT60M303 (replaced with an equivalent).
    I suppose the rectifier BG2 BR356J is working based on elementary, multimeter
    based testing by me (I am not an expert but tried to test after watching the youtube videos). I have also replaced the 470 uF 400V large Electrolyte capacitor. I have also replaced two 470uF 36V EC1 and EC2.

    Two unmarked components:
    There are two components transistors yellow (NPN), and blue (PNP) for which the
    component labels were erased. Yes the components were 'filed' to remove the markings. Based on the diagram I suppose there are regular transistors (not sure why the markings were erased).

    I am not seeing anything else burned or visibly damaged. Right now the instrument
    powers but does not start.

    Motor related:
    My motor (HN1010B), 2HP, 230V, RPM4000 motor works very nice. I mean I have connected my LIPO battery as well as my 36V cordless drill battery and the motor spins well including the belt (no friction or bearing issues). In addition, if I short the terminals with fork, it is very hard to spin it. So I suppose there is no issue with it.

    My speed sensor is also working well.
    I have seen the same TD-700, TD-350 or TD-1600 board repairs in forums but all trails went
    dead as people have either disposed of their machines or lost interest. I still like this machine as it working well. I want to make a last ditch effort before I replace the whole control board with another generic controller.

    Can someone please help me to get going.
     

    Attached Files:

  2. Tha fios agaibh

    Tha fios agaibh

    2,107
    708
    Aug 11, 2014
    I'd start by verifying your power rails.
    Do you have 12v + and 12v- with respect to ground?

    Identifying unmarked components is challenging, but you can start by unsoldering them and test them to see if they are working. Hopefully they are ok.
    You can also google "how to test transistors".

    Its also likely the transient spike blew the astar chip. You can find them on ebay for $10.
     
  3. Krishnasastry

    Krishnasastry

    4
    0
    Sep 25, 2019
    Dear Tha,
    Thank you for the suggestions. I am not an expert in electronics but just knowledgeable enough to identify and test a few components. I am doing exactly as you had suggested. At the outset a few points I am seeing the +12V and -12V as per the circuit diagram.
    Many thanks for the suggestion, I have now found a place selling the Astar-101C and placed an order! I am guessing this prefab, sealed block helps the display and/or pre-programs (P1, P2 and P3) of the treadmill. At present, the display is fine meaning, there is 400m round display in which the LED's glow sequentially (as we begin the lap) and full glow at the end and again begin it. Right now this animation is working (normally seen till we start the workout). Hence, I am supposing there is no issue with that part of the circuit.
     
  4. Tha fios agaibh

    Tha fios agaibh

    2,107
    708
    Aug 11, 2014
    I would hold off placing any orders for parts until you have evaluated the whole circuit.
    You might replace a part only to have a nearby bad part cause it to fail again.
    Also, shipping costs are high so its wise to order all parts at once.

    I would check all diodes and transistors before replacing the astar chip. If you can find a datasheet for it, that would be a big help in identifying what it's pins do and how it operates.
     
    thedoc298 likes this.
  5. Tha fios agaibh

    Tha fios agaibh

    2,107
    708
    Aug 11, 2014
    You can check diodes by unsoldering just one leg at a time instead of removing completely. They usually fail short or open circuit.
    Another common failure are photo couplers like that cosmo1010.

    It may take some time to diagnose the problem. Some clear pictures of the board would be helpful.
     
  6. Krishnasastry

    Krishnasastry

    4
    0
    Sep 25, 2019
    I am sorry, I could not update as I was intensely checking the board. I found one resistor short which is to IGBT. In addition, I also feel the thermistor SCK0120 with mild crack when seen with magnifying lens.
    I am also replacing the 7812cv 7912cv anyway they don't cost much.
    I will update again after assembling the whole board again.
     

    Attached Files:

  7. Krishnasastry

    Krishnasastry

    4
    0
    Sep 25, 2019
    Problem solved

    I am sorry, I could not update as I was checking the board, region by region.

    What I understood from the board is there are three zones in the board. 1. high current part AC to DC large rectifier (BR356J), IGBT and the High Speed Rectifier (FEP30J) and 2. there is an opto coupler part that is isolated from rest. 3. the communication between opto and the high current part.

    I went like this: Since I am not good at electronics, especially AC circuit part, I took advantage of the two input transformers 33V and 16V.

    I have independently powered these transformers from outside (not through board pins) by making external pin connectors and gave input board. I have noticed that the Opto part (16V) part is sounding ok although the Red Led will light up only when the machine receives the start signal from console. I have de-soldered the opto couplers and tested them outside. I felt this part is ok.

    I then powered the 40V part of the circuit and found the 7812 and 7912 were not ok. Showing 8v output instead of 12V. In addition, I found 8050s transistor is also not ok on board but after desoldering it was found ok.

    I have replaced both 7812 and 7912 and the 8050s (damn cheap). after this when I powered the board, the green LED came on. I was delighted.

    I then replaced the Thermistor SCK 0120, Varistor (14D571), the yellow Tantlum Box Capacitor (0.033 uF, 275V).

    After I reassembled the circuits, not fixed to the treadmill, it was working smooth (Video uploaded). So I suppose everything seems to be ok. I have to now give load to the circuit and check again. I have not done this for the following reason.

    I am not sure whether I can check in this loose connection state as the Rectifier, IGCT and the Fast rectifier are not connected to the heat sink.

    Can I know this information. In all the pictures I have seen, there is a silicon tubing with heat conducting cement between the IC and the large black heat sink.

    Is it a must to connect to the heat sink through the silicone sleeve with heat conducting cement before giving load?
     

    Attached Files:

  8. Tha fios agaibh

    Tha fios agaibh

    2,107
    708
    Aug 11, 2014
    Sounds promising.
    You can briefly test it without the heat sink but only for a few seconds. I would set motor speed as low as possible to minimum load, and check that hooking up without heat sink isn't going to eliminating a ground path.

    It's best to always use fresh thermal paste but if theres excess clean leftover on the heat sink, it could be reused in a pinch.

    It's a bit of a hassle, but you might consider just going the extra step and reassembling it heat sink and all.
     
  9. Tr0w4tr3y

    Tr0w4tr3y

    2
    0
    May 27, 2020
    Hi, sorry to reopen this post. I've been looking also for a specific IC in my TD-350. I do not know why but the value of the IC on this board was erase. I was thinking if anybody had the same board. I just need to know the part number. https://imgur.com/a/I9BsQAF
     
  10. 73's de Edd

    73's de Edd

    2,922
    1,235
    Aug 21, 2015
    Seeing that they DON'T want us seeing this units part number, and that they possibly used flat black paint to cover its top, vice using a physical wet and dry carbide paper and a wet sanding.
    Can you confirm that either use of a MEK---TOLUENE---LACQUER THINNER---METHYL CHLORIDE--- XYLENE --- ACETONE or DENATURED ALCOHOL solvent application, might then reveal the underlaying part numbers . . . . . since most of those markings now-a-days are being laser etched on, and therefore would be non soluble.

    upload_2020-6-27_11-12-47.png
     
  11. Tr0w4tr3y

    Tr0w4tr3y

    2
    0
    May 27, 2020
    Hi 73's de Edd, I tried using your suggestions but it does not show. Look like it was grinded by a dremel or been sanded to totally erase the part number.
     

    Attached Files:

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