TCI Transistor Controlled Ignition - Replacement Transistor

Paul Sutton

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I am making this entry to add some updated information regarding the choice of a replacement for the ETD41-035 transistor. Some of this has been mentioned in earlier threads e.g. Hesitation under load when Turn Signals are flashing! Lol. The following link gives the full discussion with an update:

http://www.xjcd.org/TCI_transistors

Basically the author has made a study using an oscilloscope to see how the transistor performs while the engine is running. It is found that the previously recommended replacement, MJE5742, has a significantly different time characteristic compared to the original ETD41-035 resulting in a poor quality spark. It is found that a better choice of replacement would be ST901T. This gave an enhanced spark compared to the original and has a more similar time characteristic.

ST901T is used a lot in small transistor controlled ignition systems and is currently available on sites such as Ebay for a few $s or £s.

 
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