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Post by ericsuz on Nov 23, 2023 5:14:24 GMT -5
Hi All, I am trying to resuscitate a cdi unit. Changed the diodes but still not good. I have no voltage between ground and the body of the thyristor, although I can hear the converter noise.
I understand that the black wire (#3) connected to the thyristor 2SF1188 is on the cathode. That black wire (#3) is connected to a common point of 2 capacitors (yellow wires) which are located under the lower board. So it seems that one capacitor is between that common point and one of the black wires (#1) and the other capacitor is between that common point and the other black wire (#2)
When I measure the capacitances, I find 1microF between #1 and #3, which seems ok, and a tiny 170 nanoF between #1 and #2, which seems too low.
Questions to you all: is my understanding correct on the capacitors wiring? If so, What should be the measured values? Can I try to wire a new capacitor between #1 and 2#? and which value?
Thanks for your help.
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Post by wayne on Nov 23, 2023 18:45:43 GMT -5
Where are you located ericsuz?
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Post by ericsuz on Nov 24, 2023 13:13:10 GMT -5
Where are you located ericsuz? Aix en provence, France
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Post by ericsuz on Nov 26, 2023 5:58:52 GMT -5
Update: the fault is one of the capacitors below the green board (the smallest of the 2 in-bedded in resin; it is the one below the oval opening connected between wires #2 and #3) ; I have wired a 1 microF 275v and tested the unit: it works fine but I need to make the room for it below the green board; I intend to mill the faulty cap and locate the replacement in the cavity that I create. I will post pictures.
The new capacitor is the blue one hanging around above the main board
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Post by timpa136 on Nov 26, 2023 9:35:42 GMT -5
Update: the fault is one of the capacitors below the green board (the smallest of the 2 in-bedded in resin; it is the one below the oval opening connected between wires #2 and #3) ; I have wired a 1 microF 275v and tested the unit: it works fine but I need to make the room for it below the green board; I intend to mill the faulty cap and locate the replacement in the cavity that I create. I will post pictures. The new capacitor is the blue one hanging around above the main board Thanks for sharing your repairs and those pictures will be of extreme interest.Many moons ago, my wife's bike CDI quit on a 3 day campout. One Friend brought a soldering iron, another Friend brought his Smarts as a TV repairman, I ran back into town to radioshack and bought a volt ohm meter and 2 shorted diodes were discovered and spliced in with a service loop with the soldering iron plugged into the shower/ restroom! I enjoy telling that story. Tim
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Post by wayne on Nov 27, 2023 18:12:28 GMT -5
I'll chime in as well to thank you ERICSUZ. We really appreciate your additions to this thread.
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Post by ericsuz on Nov 29, 2023 6:15:24 GMT -5
update: I have milled out the faulty capacitor, and located the new one in the cavity.
the depth of milling is 22 mm from the surface of the green board. If you do so, be careful not to damage the other capacitor. The capacitor that I installed is a 1microF 275Vac; its size is 30x22x13 mm. Available in many places.
On the other side of the box, there is a plate with 4 screws; underneath that plate is the large transistor which chops the 12V to feed the transformer. Check that the 2 screws holding the transistor are tight, since on the other side, on the main board, there are electrical connections to wires and strips on the small metal spacers.
My CDI is now singing loud and making nice sparks. :-)
Thanks for this very useful thread !
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Post by hudson on Nov 29, 2023 8:46:22 GMT -5
Ericsuz,
That is a beautiful well done repair, with a lot of very good information. Must have taken several minutes possibly hunderds.
Brian
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