Dimmer repair

Hi Walid,

If you only have off and on and when the dimmer is in the on position it is always at full brightness then the most likely problem is the Triac. You can test this with a continuity tester when the dimmer is removed from power by checking the continuity between A1 and A2 terminals. It should be open under normal circumstances. If it is shorted then the triac is bad. The other components are probably OK. The BTB 04-600A is a 4 Amp 600 Volt triac and can be replaced with pretty much any triac that has ratings of more than 4 amps and 600 volts. I have some BTB 06-600 which would be 6 amps and 600 volts. If you are inside the USA I will send one to you. If you are looking at the triac with the pins down and the label facing you the A1 and A2 terminal are the left pin and the center pin. The right pin is the gate and should be attached to a DB3 trigger diode if you have a standard design.

John

Hi John,

Thank you for your help I really appreciate your kind answer but I am too far from you that would make this triac very expensive So, I am experiencing exactly what you described and already replaced the old triac with a new one labeled BTB08-600BW (the only "equivalent" triac I found in the neiborhood) which didn'ty solve the problem. So I just tested both of them and both of their A1 and A2 show no continuity....does that mean they're both open and ok ? When I tested the capacitor I got a 0.0µF instead of 0.033µF...is it possible that my tester is not sensitive enough or is my capacitor is dead ? In that case could he be the origin of the problem ?

Best regards,

W

Looks like you found the source of the problem at least and you can get a replacement control from EBay. Sorry for all the hoops you had to jump through but the failure of a control like this is very rare and not very high on my list of suspects.

John

I really had fun testing all the possible sources of this failure and learned a lot. Thanks to all of you for your time and help and especially you John.

Take care.

W

Thanks to both of you, it's been great to see how you found the cause of the problem.

wal_e  wrote:

 

So I tried cleaning the strips with a soft clothe, sanded sofftly the wiper and rised them a bit too...reassembled the control and tested the resistance between the two legs : 0.553 when DMM is on 2 Mohm. Resoldered the control and tested the switch...worked a bit as a dimmer, heard a few "sizzlings" but still managed to dim a few times then went back to ON-OFF only...

The sizzlings are not normal. The capacitor (C1 in the schema you posted) normally drops the majority of the voltage before it reaches the potentiometer.

My guess is that if you do not replace the capacitor, and buy a new potentiometer, you will have a repeat of the issue after replacing the potentiometer..

I agree, great detective work from John and Jan.

Hi Jan,

I found an equivalent control but that's why I was initialy here: no way to find the C1 capacitor on the internet: CBB62B X2 0.033µF (250-280VAC) 40/110/56/C.

By the way, does anyone recognize the logo/name on this capacitor ? Would be helpful. Thanks in advance

This one will work for your application:

https://www.newark.com/epcos/b32671l6333j000/cap-0-033uf-630v-film-radial-rohs/dp/82AH6885?st=capacitor%20.033%20uf%20250v

John

I am in disagreement with Jan on the need to replace the 0.033 uF cap. My experience tells me it is OK and that the failure was in the control due to contamination or lubricant failure that has cause an arc path to form between the wiper contact ring and the resistive material. I am however just a technician and Jan is one of the top Engineers on the Forum so one has to respect his opinion. Depending on how difficult it is to find the proper capacitor you will have to weigh whether to use the original or replace it. On the link I gave you it is difficult to judge the dimensions of the component. You may want to check the Data Sheet to make sure it will fit before you order. The move from a 250V cap to a 630V cap will not affect operation but it may make the new one a larger size.

John

Hi John, sorry for the late reply I was away from home. In the datasheet I found the reference of the exact capacitor I need to replace thank you. You said something that caught my attention : "lubricant failure". Is the lubricant here to optimize the contact between the wipers and the stripes? Because when cleaning the control I wiped it clean and didn't replace any before reassembling. What kind of lubricant can I use ? Thank you

Hi John, sorry for the late reply I was away from home. In the datasheet I found the reference of the exact capacitor I need to replace thank you. You said something that caught my attention : "lubricant failure". Is the lubricant here to optimize the contact between the wipers and the stripes? Because when cleaning the control I wiped it clean and didn't replace any before reassembling. What kind of lubricant can I use ? Thank you

I don't really know but I speculate that the grease is there as an insulator, a conductor of heat, an arc suppressor, and probably for the cosmetic feel it imparts to turning the control. If you are able to open the control again without breaking the metal retention tabs you should inspect the insulator between the metal slide ring and the black resistive strip near the bright end of the turn as that seems to be where the short is.

John