I did something Stupid!
 

I accidently reversed the polarity to the battery in my 1975 911S, burned the alternator. I just replaced this, now it turns over great, however, it won't start. Any ideas on what else I might have damaged??
Any help would be greatly appreciated!

First off sorry to hear about this. Now since it is turning over you know your starter is still working. You should check ALL FUSES, if they are all good check for spark. If there is no spark I am thinking that you may have somehow fried your CDI or coil? But FUSES are the best place to start.

Shawn

Without a doubt, you blew out three transistors in the CDI unit ... a 2N3055 (world's most popular transistor) and a couple of PNP medium-power switching transistors that probably can be replaced by a 2N2904. Maybe a couple of Zeners as well ... if you can handle a soldering iron, or know someone who can, it can probably be fixed. If you want to try, let me know, and I will send you the schematic and parts layout.

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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

"three transistors in the CDI unit ... a 2N3055 "

There is only one of these inside mine http://www.pelicanparts.com/ultimate/smile.gif at least in Bosch 3 pole -71 version. Then there are two ON200A transistors which are not found in any books. Philips is the manufacturer but I asked them and they don't know jack about which modern transistor could be used in their place.

U sure about 2N2904?

This is what I got from Philips

Dear Mr. Kosonen,

We're sorry we were not able to provide you with some more information.

In the future, should you have any questions please do not hesitate to contact the Philips Consumer Center. The telephone number is: 0900-8406 (22 cents per minute) and can be reached from Monday till Friday between 8am and 8pm.

With kind regards,

Wouter Janssen
Philips Consumer Center


HMM, like I would like to call Netherlands to know what transistor we are talking about, thats what the internet is for.

Zen,

I am sure enough to install a pair of 2N2904 transistors in sockets in my previously working unit ... and I will let you know whether it continues to generate lightning bolts when triggered.

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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

If it works better, let us all know =) !

After all, the transistors are newer so, you never know.

Theres always a freeplay when building electronic devices, wonder if one could replace those 2 transistors with higher amlification factor to gain more crisper spark at the end.

I have nothing to add here other than I could start pretty much all my posts/inquiries with the exact same heading.

Joe 68L

Thanks so much for your help. Unfortunately, I am but a novice - what is the CDI and where is it located. I have a good idea, but need confirmation. I also would appreciate any schematics that might help. Again, thanks for the help.

Ahh...2N3055 ... brings back memories. I made tons of amplifiers and all other stuff with those. http://www.pelicanparts.com/ultimate/smile.gif My favorite transistor...

Just to add. I still hear the high pitch whine when I turn the ignition to the on position. Would this indicate that the CDI is still functioning?

If we're name dropping "favorite" components.... I guess mine is a 6L6.
(That's a vacuum tube, for you young'ins!)




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'81 SC Coupe (aka: "Blue Bomber")
Canada West Region PCA
The Blue Bomber's Website
"If it ain't broke...we'll help you fix it 'til it is!"