TCI diodes

[jeff1]

Per recommended on this forum I decided to check the diodes in the TCI on my '89. To me they look OK. There are 2 Diodes in the center of the board in line with the 8 diodes that I see are normally replaced. They are marked ZD1 and ZD2 and appear discolored so I have 2 questions.

1) Should I replace the 8 diodes regardless of they look?

2) Does anyone know anything about the 2 diodes mentioned above?

The bike runs fine. Inspecting this board is strictly preventive. As far as I can tell this TCI is original. The bike has 90K on it.

Thanks in advance

Jeff

[pmelah]

i think this would be a Dingy question/answer as it all looks good to me

[bongobobny]

ZD1 and ZD2 are Zener Diodes which are "special" diodes. A Zener diode clamps the voltage to a certain value and keeps it there regardless of how much the applied voltage changes (as long as the voltage is above the value of the Zener). In your picture they look like they should look. If those diodes were bad the unit would not function correctly...

[dingy]

If you are that far in there, I would replace the 8 barrel diodes that have been known to fail. All the ones that have failed looked good also when new. I don't know what causes the failures of the diodes, probably moisture contributes to it.

 

But once they fail, the TCI is pretty much junk.

 

Picture is of bad diodes in center of photo. One has already fallen off, wires on either end are visible just above the two blue & gray diodes in center.

 

Gary