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

I just thought of another possibility. It is possible that the wiper inside the control has come loose from the shaft and has limited mobility near the low end. Bend the metal tabs up and open the control and check it out. You can also test the carbon strip by putting your meter from one end to the other. I bet we will see 500K or there abouts. If the wiper is loose perhaps you can fix the control by reattaching it.

John

Yes that looks like a good replacement.

Here are the photos from inside the control:

Please let me know if you have any remarks regarding their looks. I noticed that the inside is quite "greasy".

Which part is the wiper ? the one attached to the plastic white rotating knob ?

The mesure of the outer strip is 0.555 when DMM is on 2 Mohm.

wal_e  wrote:

 

The mesure of the outer strip is 0.555 when DMM is on 2 Mohm.

That is normal, for a 500K potentiometer ...

That's what I thought too...so is there any way to fix it ? Should I clean the wipers with soft sand paper and rise them a bit ?

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...

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.

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

I agree, great detective work from John and Jan.