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Join Date: Jun 2006
Posts: 14
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OEM CDI repairs 84-930 T
Has anyone worked on the electronics in the CDI box, what component usually fails, are schematics available?
Mike PS: I know pelican can have it rebuilt, I love to play with elc. so thought I would try to fix it myself just for the fun of it. |
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06-12-2006, 09:20 AM
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Location: TX USA
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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06-12-2006, 09:26 AM
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Thanks S Man
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06-12-2006, 09:29 AM
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What seems to be the most likely component to fail in CDI when they quit when hot then restart for a while then get to the point where they will run for a few seconds and quit.
does cap c8 fail often, does the scr fail often Mike |
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06-13-2006, 08:38 AM
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Mike,
Thanks for pointing out the transcription error on the schematic bridging the two Zeners ... I corrected it in the thread after going back to my hand-drawn pencil version and noticed an extra 'bridging' connection. Funny how errors creep in when you try to make a drawing prettier and more presentable! The most common problem when there is an intermittent failure is bad connections to the board where the 15 wires to the chassis-mounted components terminate. Wires can be cracked or solder joints can deteriorate due to vibration, corrosion due to encroaching humidity, etc. Sometimes internal connections within components such as capacitors, transistors, SCRs, or diodes can fail and be intermittent, too. Yes, C8 and the SCR do occasionally fail, but that is pretty rare. T1, ZD1, T2, T3, T4, C7, and D8 also fail on occasion. An interesting factory option from Bosch that Mercedes specified was that a black rubber-based sealing compound be used to seal the back cover! Porsche did not specify the sealing compound, but it seems like a good idea. A modern silicone GE sealant would seem like a good idea!
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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06-13-2006, 09:38 AM
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another oops,[been there done that way too many times myself] , c2 needs to go to the other ends of r5,r6. thanks for your help, you sure made it easier for me. now lets see if I can really fix it. so far found corroded c2, upgraded c8 and scr
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06-13-2006, 10:00 AM
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OOH! OOH! OOH! its working, DXed C2, C8, SCR. Need to button it up and take it for a spin, cross your fingers.
Ever greatful to Warren, Mike |
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06-13-2006, 11:10 AM
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correction, DXed C1 not C2, SCR with Motorols MCR65-8 ,C8 1.5/600 mylar
all for 20$ in parts |
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06-13-2006, 11:18 AM
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Now, THAT is the kind of ending I like to hear about with CDI problems! Nice to be able to find those replacement parts locally, too!
Congrats, and great job done!!!
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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06-14-2006, 06:01 AM
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