cdi unit to a motorcycle

[Jeffro]

I have a cdi unit to a motorcycle thats over 30 years old that crapped out on me. I narrowed it down to the cdi as I have no spark to my ignition coils. I am not an electrical person by any means but I can unsolder and resolder components. My issue is that I don't know what I'm looking for. I've been reading that a bad SCR is what usually goes bad in these but I have no idea what it looks like. I see no bad solder joints either. Can someone please help me?

 

[BradtheRad]

This looks like the best bet to be an scr. You have two of them. Can you get at their solder joints on the other side? However it's too soon to remove them.

Tell us all the lettering on them. It can't be seen due to glare.

 

[Jeffro]

Ah, those. Fuji 5N D1071

 

[Easy peasy]

It doesn't appear to be CDI as there is no 500V storage cap, or step up power stage, just transistor assisted, after 30 years could be solder joint(s) or the transistors used to energise the coil ...

 

[Easy peasy]

there appears to be a broken SMT part middle left too ...

 

[Jeffro]

By the manual its called the ignitor.

 

[Jeffro]

Broken SMT part?

 

[BradtheRad]

Several components next to the scr's appear to have black deposits. It's hard to tell if they're charred, or perhaps they attracted carbon particles. Can you confirm what it is?
There's a chance it results in unwanted current flow, causing malfunction.

By cleaning away the deposits you may get the unit to work again. The components are hard to get at. To clean properly is the big hurdle. It might be done with solvents, and/or brushing. Maybe even sandblasting.

 

[Jeffro]

Its actually just some goopy crap that is sporadically present and causing glares from the photo. This PCB was in a sealed plastic case until I opened it today. I examined all of the solder joints under magnification and didn't find any solder joint breaks or anything strange.

 

[FvM]

2SD1071, NPN darlington transistors 6A/450V, not SCR. I would at least check that they have no CE short. But it can be anything, e.g. dried out electrolytic capacitors.

Is it a two-cylinder, two-ignition coil configuration?

 

[KlausST]

Hi,

I wonder how an SCR can be used as ignition trigger.
Usually the coil gets activated current flow, ... end when released (switch open) high voltage gets induced to trigger the ignition.
But an SCR opens when there is about no current...

Klaus

 

[Jeffro]

Its a 4 cylinder bike with two pick up coils. Is there a place I could send this to and have it rebuilt?