TCI ignition capacitor and transistor replacement

[wallywheels]

Ok A few days ago, a bike I helped a friend build was finished and all was well until the volt sensor wire came disconnected form the reg/rec and caused a spike in voltage. I believe around 18v was as high as it got. Then the bike died. I fixed the disconnected wire to the reg/rec and went on to try starting again and no spark. I traced wires until it lead me to the TCI box and I swapped it out for a good one I had. WALLA!! it fixed it so I knew it was the ignition box. I took it apart and found a melted capacitor and a bubbled Transistor so I did some research and found the matching parts from www.digikey.com Here is what I replaced
Transistor part # MJE5742GOS-ND
Capacitor part #P15798CT-ND
I have also read the 4 resistors D1-D4 can go bad but mine has good resistance so no need to replace at this time.I put it back in the bike and it had great spark and runs great!

 

[retiredgentleman]

Good repair job..................well done

 

[wallywheels]

Thanks Ret. Gent. always love to save a buck when I can. Time will tell if it holds up but I don't see why it wouldn't.

 

[TwoManyXS1Bs]

Is that a 'factory' TCI? Is that a single-sided board? Does a schematic exist for those? If not, can you draw a 'reverse-engineered' schematic? RG, would that be useful?

 

[Tomterrific]

One of the 'Ricks' over on the yam650 list rebuilds TCI boards for folks. It is a good analogue electronic ignition. I'm always wondering if a sturdy modern power transitor could be substituted for the original so a lower ohm coil could be used.

Tom

 

[TwoManyXS1Bs]

Sorry for the previous post, got excited, blurted early. Then scanned this forum and found at least 3 variants of that board. Opened a can of worms here...

 

[XSLeo]

The D1-D4 are not resisters, they are diodes. They let electricity flow one way. You need to disconect one end of the diode soit can't backfeed around it and test the ohms both ways through it. One way will be low ohms the other much higher. The common difference should be at least 10 times as much ohms one way as the other.
Leo

 

[wallywheels]

Oh good to know if it starts running funny I will check the diods next I am no electrical engineer thanks for the correction