[atownbrg]

I put a wanted ad in the forum, hope its allowed to post something like this here. Its where the folks actually are that may have one!
Does anyone have a "BAD" cdi and / or change relay kicking around? I'd like to get a couple and disect. Eventually interested in seeing what it would take and cost to reproduce.

 

[knauff13]

I no longer have the CDI but I think I still have a bad ignition coil and possibly the change relay for a 78 CB400a. Not sure if they are interchangeable between 78-81.

 

[atownbrg]

Im not sure either if there is a difference, but that is something that would be good to find out! Definitely interested in your '78 change relay. I will send a PM.
Thanks
Pete

 

[longdistancerider]

The change relay is the same for all years/models, only 1 part number 38320-417-008

 

[atownbrg]

Just an update,
I received the change relay from Knauff13 (thanks). Have not been able to obtain CDI as of yet. I have begun to remove the potting compound using a heat gun and pick tool. Realized my "homeowners" heat gun is too big (lots of excess heat on my hands and tools), I've ordered a hot air desolder tool in hopes that I can have a bit easier time. Have already got burns and blisters from blasting and picking at that damn epoxy its rock hard and although it does soften up slightly, you have to keep the heat on or else it just goes back to being rock hard mass!
I'll admit i'm over me head on this, at least as far as backward engineering the specs of the transistor and resistor values used. I've joined in over at allaboutcircuits.com to try to get some help there.
Here's a link to my thread:
https://forum.allaboutcircuits.com/...tage-motorcycle-how-to-identify-parts.155882/
I'm hoping that i can identify the components used after removing the potting compound, but it would be nice to also understand the circuit analysis part of it.
I thought it would be easy hahahahahah

 

[atownbrg]

The hot air desolder tool worked alot better than the wagner heat gun, but still required alot of heat. Was very hard to keep from destroying everything. Unfortunately most of the components appear to be surface mount and I really have no idea how to identify any of it as far as part numbers or values go....
The two wires that go to the CDI unit were soldered to a larger board with traces that in turn were connected to another circuit board that held the solid state components of the change relay. That board was white and was made out of a ceramic type material. Everything was so SMALL! The larger square on the penny is whats left of the transistor and the other square dot is either a resistor or diode. When I lifted up the white ceramic piece, some of the components were attached to that, and some were left behind in the potting compound below, including parts of the traces. both boards were sandwiched together with compound in between. There ceramic board was actually in the bottom of the cup of the whole enclosure, I had to cut off the back to get to it.

 

[longdistancerider]

I think you're back to square one here, too much heat. Looking at google for ideas they mention using acetone, soak-scrape, soak-scrape, repeat for days.

 

[Chainman]

I have a cdi from a 1980 cb400t that you are welcome to have.

 

[atownbrg]

"I think you're back to square one here, too much heat. Looking at google for ideas they mention using acetone, soak-scrape, soak-scrape, repeat for days"

Its true, not much accomplished. I wasn't expecting to see surface mount components in there. Those are probably hard to identify even if they are in good shape. I took alot of pictures and should be able to get the 2 circuit board trace patterns figured out.

"I have a cdi from a 1980 cb400t that you are welcome to have"

Chainman, I'll send you a PM. Although the CDI for the Automatics are different, I wouldn't mind checking out yours, I'm sure some of the components would be similar, and how it was put together overall would be too. Thanks!