Dimmer repair

Hi,

If rotating the dimmer makes it turn the light on and off, then why do you think the triac is faulty? Couldn't it be the rotary potentiometer? (I don't know - I'm speculating).

I'm not sure it is good to replace with alternatives if the original parts are unavailable in your region, and there's assembly risks too (e.g. replacing it may require replacing insulating washers).

Anyway, I think you need to consider that it could be something else faulty. By the time you replace the triac and/or capacitor, and then discover you now need to order something else, all that plus your time will cost >> than a new dimmer, and may be >> unsafe.

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

Hello Shabaz,

Thank you for taking the time to answer. I found this diagnostic on the internet, it says that if the dimmer only works from OFF to ON max power it's a triac issue.

As you can imagine this is not a vital issue but I like fixing things instead of just replacing them I can't help it .

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

Hi Walid,

It sounds like you got a good substitute for the triac. If you have an analog dial type multimeter you can test the triacs with the meter. Put the range on Rx1 and put the leads on A1 and A2 of the triac. Now use a small screwdriver to short the gate to the center A2 pin. A good triac will go to low resistance and stay there until you remove the meter leads or short A1 and A2 together. To continue your trouble shooting test switch the polarity of the meter leads on A1 and A2. Connecting the gate to the center lead should again cause the triac to go low resistance just like before. Triacs are designed for AC so the conduct in both directions. Next step is to test the diac which is a small two lead device attached to the gate of the triac. It should not be shorted though it may conduct in one polarity. As long as the capacitor is not shorted it is probably ok.

John

Hi Walid,

I looked a little closer at the standard dimmer circuit and the capacitor is also quite important. My schematic shows a 0.33 uF but that is probably for 115 VAC and you are probably working with 230 VAC. If your meter can check capacitors the 0.033 should not be too small for it to read. It should indicate 33 nF. I was wrong before about testing the Diac. It should not show any resistance in either polarity on your ohmmeter. Diacs do not break down and trigger until they are in the area of 30 V plus.

John

Hi John,

My meter is digital and unfortunatly not a fancy one...I tested both triacs, BTB04-600A shows 1.9 mega ohm between A1 and A2 and goes to 0.6 kilo ohm when A2 and Gate shorted. BTB08-600BW shows 13.3 mega ohm and then 80 ohm when A2 and gate shorted.

I tested again the original box capacitor and it shows 0µF instead of 0.033 µF (or OL?). I have a spare polypropylene capacitor marked 333K (and 400VMY) which should be 0.033 µF but when tested it shows 677 µF :/

I found another spare polypropylene capacitor marked 103K (and 630 FN) and showing 0.1 µF when tested, maybe this one could replace the original one ?

What do you think ?

Thank you in advance.

W

wal_e  wrote:

 

Hi John,

My meter is digital and unfortunatly not a fancy one...I tested both triacs, BTB04-600A shows 1.9 mega ohm between A1 and A2 and goes to 0.6 kilo ohm when A2 and Gate shorted. BTB08-600BW shows 13.3 mega ohm and then 80 ohm when A2 and gate shorted.

 

The TRIAC measurements are OK

I tested again the original box capacitor and it shows 0µF instead of 0.033 µF (or OL?). I have a spare polypropylene capacitor marked 333K (and 400VMY) which should be 0.033 µF but when tested it shows 677 µF :/

I found another spare polypropylene capacitor marked 103K (and 630 FN) and showing 0.1 µF when tested, maybe this one could replace the original one ?

What do you think ?

Thank you in advance.

W

OL is usually range overload. That means that te capacity is higher than the DMM can show in the active range.

33 nF is typically supported by a DMM. Does your meter have an option to change range for capacity measurements?

333K is 33 nF, So that is a good one.

I found another spare polypropylene capacitor marked 103K (and 630 FN) and showing 0.1 µF when tested, maybe this one could replace the original one ?

That's also an off measurement. 103K should be 0.01 µF / 10 nF.

I would not put a 10 nF where the 33 nF is expected ...

Hi Jan,

So I can solder back the original triac on the pcb ?

My DMM has auto range selection I can't change anything, in the manual, for capacitance it says :

Measuring range 600 µF -> résolution 0.1 µF

Measuring range 6000 µF -> résolution 1 µF

In both cases: accuracy : +- 4% reading + +3digits

So I tried putting back the original triac and replacing the capacitor with the 333K and it didn't work...same problem: from OFF to ON max power but no dimming function...