Dimmer repair

Hi John,

I am really glad to see that here are persons like you whom put all that effort to help others. So, I changed the Diac and nothing changed still from Off to On full brightness. This, with your last message about the importance of capacitance lead me to think that, in fine, it's the capacitor that's dead or faulty and unfortunatly I couldn't find the exact same one to replace it. I took some photos of the controller and the DMM I borrowed from a friend so if you have any suggestions or ideas please let me know, I would be happy to explore further more.

Best regards,

Walid

If you put the DMM in the 200 nF range,it should give a good measurement of that cacitor. : The value 33 - or something within 10% of that.

You need to fit the capacitor legs into the 2 slots with capacitor symbol.

Discharge the capacitor first.

It's indeed a good DMM.

Hi Jan,

I tested both: brown one on the PCB and the yellow - original one, they both read 00.0 µF :/ I am even starting to doubt the DMM....

I found this page which I think is quite interesting and clear :

https://www.astuces-pratiques.fr/electronique/variateur-a-triac-fonctionnement-et-schema

Is this how you measured them? If yes, I think they are defect.

Good call on your note of caution JW. Nastie sparks can happen when you fail to recognize the isolation.

I would like to know if the lamp lights with the DIAC out of the circuit.

John

I couldn't put them in the dedicated slot since both have already been soldered and thus have short legs I used the DMM leads. BUT, I read an article about dimmers and how they work and can generate parasites and just figured out  that the capacitor I have been testing and changing the whole time is the one in charge of reducing these parasites along with the coil...and looking closer I saw a smaller capacitor that you can barely see on this photo behind the big one:

No John, the light stays off whithout the DIAC...

Thanks for running the experiment which confirms that the Triac is OK and that the Diac is also OK.  Verify that the resistors have the proper values and then the only thing left is the capacitor.

John