Transformer on Bosch 3 pin CDI defect.

[HKZ Bob]

Hello ist somebody re-winding Bosch CDI transformers ?


This one is bad. Burned I assume.




Bob

[Early_S_Man]

Bob,

I don't see any burnt windings there. The magnet wire looks fine. And, just as important, the tape wrapping the windings isn't burned or charred, either!

It does look like the main 1.4 uF cap has lost a bunch of gunk and it caused some rust and corrosion.

[HKZ Bob]

Warren I replaced this tranformer buy and good one from an OK CDI. The box was working.
100% the transformer is bad.

I took it out and drilled out the rivets. The magnet around the coil was broken severl times.
I already found a replacement a DIN part for the magnet.
Ferrit,E-Kern,Kernsatz,3800nH,N67,E42,21,15


I will replace the magnet and rewind the 1 mm coil.

Bob

I let you know if I had success fixing it.

Bob

[dorel_81]

Hello, did you re-winding Bosch CDI transformers? Please give more detail about coil diameter and number of turn.

[Alfasrule]

Just completed rewinding a transformer for a 3 pin CDI. I used the cores recommended above.
It works great. Had to change value of C11 to get the desired frequency of 3K Hz. I had to change it to a .47uf. The box works great in my test fixture. Sparking to beat the band! Got the cores from Digikey

Invalid Request

[HKZ Bob]

Great job good to See that you confirmed My post.

[dicklague]

Wait a minute......that was only 7 years between posts? That transformer rewinding must be a very time consuming job.

I am impressed that you rebuilt the transformer and the whole CDI very cool.

I just took my Bosch 3 pint box out and put in a good modern CDI. A Daytona-Sensors CD-1. I am going to clean up and fix up my old Bosch. I want to keep it around so that my 1973 will be stock as delivered. What should I replace inside just to update it? Caps? what else?

But the battle I have is that the new CDI is so much better that I want to run the car with this one. I guess that is what 40 years of technology can do. And we thought the Bosch was so cool back in those days!!

[HKZ Bob]

Wait two minutes. I am impressed that this forum bundles so much knowlage.
Buying New can be done buy everyone. He fixed his transformer. He is cool.

[Alfasrule]

I just found this POST in my research. It didn't take long to rewind this transformer. I only had to rewind W1 and W3. The wire is common transformer wire. W1 is 18 gauge, W2 is 27 gauge, and W3 was just a 10 inch piece of braided wire. W1 & W3 are wound counter clockwise and W2 clockwise.
I also went crazy this weekend and installed this Bosch System in my Alfetta.
Took a while to time it, but now she purrs like a Kitten. It never ran this smooth.
Here's a few pics. The rewinded transformer box, my setup and the unit installed in the car.

[dicklague]

Originally Posted by HKZ Bob

Wait two minutes. I am impressed that this forum bundles so much knowlage.
Buying New can be done buy everyone. He fixed his transformer. He is cool.

I too am impressed that he rebuilt it. I am going to do the same to my old 3 pin box as well. I will fix and it polish it up and put it on my 911 parts shelf.

I am installing a different CDI for now because I want more modern tech such as, a soft rev limiter, and more power at the plugs.