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Old 06-10-2021, 12:09 PM   #1
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Join Date: Oct 2015
City & State: Cambridgeshire
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Default Honda CX500 Motorcycle CDI ignition unit

Hi everyone. Not a old computer monitor this timer its something a bit different.
This is a CDI ignition unit from a 1980 Honda CX500.
In 1980 all Japanese bike starting replacing the mechanical contact breaker points ignition system with these fully electronic Capacitive discharge units. But trouble is like all electronic components they fail with age and these CDI units are are no longer available. That's progress they say ??? Luckily I found a second hand one thats still working miraculously so can use that to get readings from.
Not just that but these CDI units are placed in a steel box and then filled with a resin sealing them tight inside and away from water ingress. I was lucky this one had a slightly softer resin that was almost rubbery and I found I could pick at it with model knives and tiny screwdrivers. It took me 2 days to get it out and then pick away at it to reveal all the components. Many say the main reason these things fail is poor solder joints and they do look a bit rough.
Well It was inevitable that a few things might get damaged removing all that resin and I broke 4 resistors and slight damage to one diode and one capacitor,
Here are some photos of the unit at different stages.
At each end of the board there was a strange twisted wire resistor thingy I have no Ideal of its purpose. There are a few transistors also but they have no markings.
I managed to remove the resin from the bottom of it revealing the printed circuit as well.
Please can anyone help me identify any of these parts apart from the obvious resistors etc. None of the caps are marked either but there are no electrolytic ones.
I removed the two main output Capacitors to get access to the components underneath.
Please please help guide me to getting this rebuilt with the faulty parts replaced as its the only way this bike will run when this current still ancient unit I am using also fails.
I have uploaded more pictures at
Attached Images
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File Type: jpg 20210610_182151.jpg (210.5 KB, 31 views)
File Type: jpg 20210610_182123.jpg (189.8 KB, 26 views)
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