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Dimmer repair

wal_e

Hello everyone,

First of all I would like to apologize, I might certainly be in the wrong section, but I have been sent here by the Farnell technical assistance and to be honnest this place is a real maze for me image

So, I have been trying to fix a dimmer that went working only as a simple switch : OFF to ON max light directly. Following my researches it seems that the origin of my problem is a faulty triac and also - maybe - a capacitor ; I have tested both of the 2 fuses and they are ok.

The two original component are labeled:

- BTB04-600A

- CBB62B X2 0.033µF (250-280VAC) dimensions 40/110/56/C

My problem is that I can't find any of the exact two components and I have no idea what I can use to replace them as equivalent.

Any help is really appreciated

Thank you - very much - in advance.

 

W

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  • 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

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  • 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

Children
  • in reply to jw0752

    image

     

    I extracted this rotary dimmer circuit schematic from a video. I added the letter references. A=Load and B=neutral.

     

    If I read your explanation correct E & B sides of the triac will read low resistance when the gate F is triggered. Reverse the leads across the triac and it should provide a low resistance reading also.

  • in reply to colporteur

    Hi Sean,

    This test works best with an analog meter that uses at least two batteries (3V) in it's Ohmmeter function. Range Rx1 is also best as this delivers the highest current to the device under test. This is because the triacs need a minimum current to keep the triac A1 A2 junction saturated once it is triggered. The triac should be tested with both polarities on A1 and A2. Once the Triac is triggered you can reset it by shorting A1 to A2 or by removing one of the test leads. 90 percent of the time this test can be performed in circuit as long as the board is powered down.

    John