1980 930 and 1974 911 6 pin CDI box the same
 

I own a 1980 930 and 1974 911 with 3.0 w/ webers.

I just had my 1980 930 Bosch CDI box rebuilt due to a really low whine, also installed new Bosch coil.

I recently purchased a 1974 with 3.0 w. webers. Car runs fine, but when I turn car on I get NO WHINE from CDI box at all.

With my new 930 box it is extremely loud.

I know for a fact both boxes are Bosch 6 pin boxes. I wanted to swap the boxes and see if I hear the whine in the 911 with the 930 box. Are these boxes the same?

Would my 911 CDI box be working if it wasnt whining?

From the part numbers they are the same.
Maybe each box whines at its own level, like kids...:)

this was all prompted by a jumping tach,...

I replaced voltage regulator and nothing, it only does it at the higher RPMs...

after watching the video a few times on ecudoctors.com this occurred to me

Of course you realize that the '74 had a 3-pin originally...and the 6-pin was added with the 3.0.

Yes. I know this is not the box that would have been there for the 2.7