1. Having trouble logging in? Try closing your browser and re-opening it. If that doesn't work, try a different browser or device. The site will be updated soon to resolve these browser issues.
    Dismiss Notice
  2. Dismiss Notice
  3. Hey Facebook people... We've created a group for XS400.com members to connect. Check it out!
    Dismiss Notice
  4. Want an XS400.com t-shirt? Go to the store to order. Limited sizes and quantities available.
    Dismiss Notice

My success in repairing a TCI box

Discussion in 'The Garage' started by Kitchi, Aug 11, 2022.

  1. Kitchi

    Kitchi XS400 Enthusiast

    This is my diclamer
    this is what i did and it worked for me.
    If you do the same and it dose not work or the magic smoke is released that is on you I accept no responsibility.

    This is what i did I de-soldered all the transistors and tested them in a cheep tester i bought from china years ago. all them tested fine.
    I proceeded to test the resistors, they tested within specs.
    I removed all the electrolytic capacitors and tested them.I found one of the capacitors to be way out of spec I believe C15. from memory I believe the value of the Capacitor was 2.2uf at 50volt polarized.
    From experience in electronic repair I know the majority of the capacitor that were produced in the 80's by now(usually) can be defective so I replaced them all.
    And re-soldered all the solder points.

    I removed all that brown goop from the board. If it is the same material that I have run into in the past It can become conductive.I used hot glue in its place.

    After assembling the TCI unit I tried to devise a way of testing the unit before reinstalling it back in the bike and (right or wrong) this is what i cam up with.

    I powered the TCI unit with my bench power supply limiting the current to 1 amp and checked the components in the unit for excessive heat (just in case i made a mistake) for 15 ish minuets.

    Then i connected 2 analog multi-meters(old school meters that have a sweeping needle not a digital display) to each of the outputs that go to the coils and set the meter to the 20 volt range. You should have zero volts on the meter.If you don't have these meters a light bulb could be used as a sub-statue. such as one for a license plate or another one that is low wattage.
    To simulate the pick up coil i used a triple a battery. negative to the ground and touched the positive of the battery to the input wire to the TCI unit and immediately removed the wire. then looking at the meters (or lights) i noticed one meter climbed to 12 volts (or there abouts) and decayed back to zero volts in a seconds or two.

    Then do the same to the second coil input.you should see the same result on the second meter or light.

    If all is right you should have a functioning TCI unit unless something funky is happening with the integrated circuit that is on the board and unfortunately there is no data on that IC.

    At this time if the IC is damaged the TCI unit is unfix-able.

    I wish I documented this but at the time i didn't think of it.

    IMO the majority of these TCI units should be able to be repaired. with the exception of the IC (integrated circuit) replacement parts (identical or substitutes) are available from electronic suppliers.
    the IC seemed to be either a one off maid specifically for this application or a common part that has a different part number on it to prevent cloning the box.
    most likely it has a different part # on it.

    The Capacitor I replaced looks like it controls the decay rate of the output voltage. If there is no decay or not enough decay you will not get proper spark.
    so it is important that the replacement capacitor has the same value as the original.

    My terminology I have used in this rite up is not 100% accurate as i am only an electronic hobbyist. I tried to make this easy to understand so someone with little electronic knowledge might be able to get something out of it.

    I hope this helps someone out.
    I there are any questions please feel free to ask and I will try to answer them the best as i can.

    Steve from Northern Ontario
    JPaganel, CaptChrome and Buddha like this.
  2. Buddha

    Buddha XS400 Addict Top Contributor

    Steve this is an awesome write up on repairing the TCI
    Kudos to you
    CaptChrome likes this.
  3. CaptChrome

    CaptChrome XS400 Addict

    Steve - thanks for this. I have read a bunch of stuff on TCIs, and I hope that when I get to start my bike that the TCI is good. However, if it is acting up, this will be the first article I read in order to troubleshoot the board (and ask questions!). Many thanks for the time you spent to get it out to us.

Share This Page