XS1100 TCI inner workings

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This is a look into the Yamaha XS1100 TCI or Transistorized Control Ignition. Today it would be referred to as an ECU or Electronic Control Unit. The unit uses a sensor which is a tiny coil of wire mounted down on the left side of the bike. 2 sensors total 1 for each coil. When the magnet or "reluctor" passes each of the two tiny coils of wire inside the sensor, it sends current to the base of each transistor. The transistor then turns on like a tiny relay and grounds the large ignition coil for a short period of time. During this time, the coil charges up and then releases a huge burst of stepped up voltage that can actually jump the small gap at the end of the spark plug. All timed perfectly with mechanical devices.

Here is a diagram that's a little more in depth in comparison with what they provide in the service manual. The colors highlight some more detail in the circuit.

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The transistors in the TCI are NPN or "Negative-Positive-Negative".

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This is how the transistor in the TCI makes spark.

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To remover the circuit board you must de-solder the pins that go to the spade connectors that are potted to the TCI plastic housing. The spade connectors are not removable and are easily destroyed if overheated. Conformal coating is used to protect the circuit from weather. It's a clear type of epoxy that must be removed and replaced after any repairs are made. These chemicals are available through electronic supply vendors.

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A guide to what wire goes where on the TCI plugs.

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De-solder pins and carefully remove circuit board.

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The actual TCI board. The two large silver circle items are the old fashioned transistors. Lots of capacitors. A few small transistors. Lots of resistors. A few diodes.

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Someone on-line posted this schematic on the XS1100 TCI. It is in German but can still be followed from known pin-out information.

[XJkid]

You guys are Geeks.

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This is a very basic path for output the ignition coil. Start at the left with the sensor and all the way through to the large ETD32 transistor. Many smaller transistors involved.

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If you have only one coil working and have traced it back correctly to this TCI then the problem is more that likely one of the big transistors. The clue is the huge heat sink on the devices. Usually the first part to fail in a circuit is one that gets hot.

[DEEBS11]

ETD32-035B. TO-3 configuration. Anybody know of a resource for this part? I'm sure it just about impossible to find. Probably went obsolete in the 1990s. Must be some on a shelf somewhere.

[Mathh]

ETD32-035B. TO-3 configuration. Anybody know of a resource for this part? I'm sure it just about impossible to find. Probably went obsolete in the 1990s. Must be some on a shelf somewhere.

Well, I googled and found this: https://www.transistorall.com/transi...rch=ETD32-035B

[dansmith65]

ETD32-035B. TO-3 configuration. Anybody know of a resource for this part? I'm sure it just about impossible to find. Probably went obsolete in the 1990s. Must be some on a shelf somewhere.

I love that you're doing this! Here's what my quick google search turned up:

• https://www.transistormosfet.com/tra...rch=ETD32-035B
• https://www.exshinetech.com/products...TD32-035B.html

[LAB3]

Wonder if it wouldn't be easier to try mapping the input and output and running it with an Arduino?