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

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

wal_e  wrote:

 

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.

I believe you have to use the two slots for capacity measurements.

Well that would make perfectly sense....I will use wire extensions and let you know

So here are the mesured values:

C1 (yellow original one) labeled 0.033 µF reads 3.1 when DMM on 200 nF

C2 (small capacitor behind the big one) labeled 683K reads 70.1 when DMM on 200 nF

R1 (red, red, orange, silver or grey) supposed to be 22 Kohm reads 0.02 when DMM on 2 Mohm

R2 (blue, grey, brown, gold) supposed to be 0.68 Kohm reads 0.665 when DMM on 2 Kohm

C1 is not OK

C2, R1 and R2 measurements are OK

Thank you for the feedback Jan, problem is from what I understood C2, R1 and R2 are part of the main syteme that works to dim the light...C1 and the coil are here to reduce the amount of parasites emitted by the Triac and thus are "optional"....still the system doesn't work...

What is minimum and maximum resistance of the control?

Can you please be more specific ?

The knob that you turn to select dim or bright is a variable resistor. It has two terminals that attach at the edge of the board.  When it is at dim I would expect a reading of several hundred K Ohms . When it is at the bright position I would expect a low Ohm reading.

John

The knob that you turn to select dim or bright is a variable resistor. It has two terminals that attach at the edge of the board.  When it is at dim I would expect a reading of several hundred K Ohms . When it is at the bright position I would expect a low Ohm reading.

John

That knob is also used to go from OFF to min light, at that point (even when in off position) it reads 14.6 when DMM is in 20 Kohm and when max bright light it reads 1.8 when DMM is in 200 ohm.

See if you can remove the solder from one leg of the control so that it is separated from the circuit trace. Try the dimmer with power on. The light should stay off. Unplug the unit and check the resistance of the control again with the one leg still detached. When you read the meter watch to see if a "K" is displayed with the number on the display. What are the minimum and maximum position resistances?

John

Hi John, I "drew" the circuit of the dimmer. Here the control is labeled P and has 3 legs: 2 that you can see on the other photos and one under it. Please let me know which one I should remove the solder from.

Walid, can you double-check the circuit around the potentiometer P and R1?

On your circuit that looks like a dead end. It only has one wire connected to the circuit.

Hi Jan, sorry I indeed forgot some part of the circuit but it doesn't involve the paret you pointed. Here is a corrected drawing and the photo of the back circuit annotated.

My mistake, phase in is lower. Here is corrected:

Hi Walid,

The two connections at the center of the board are the ON OFF switch . If you can remove the solder from either of the other connections at the edge of the board so that the metal leg from the P control no longer touches the copper you will be able to perform my experiment. Nice job on drawing the schematic. I am not sure that it is totally correct as the switch isn't where I would expect to see it in the circuit but who knows. This experiment is to verify that the control is working properly. Once the leg of P is no longer touching the circuit copper traces you will have to touch the meter to the two legs to get the resistance readings.

John

Thank you John. Am I supposed to test it while light is at max light or dim ?

We need to get a resistance reading on the two legs closest to the edge of the board in the dim position and the bright position. Make certain there is no power to the system when these readings are made or you may damage the meter.

The holes are too narrow the legs are still touching the pcb...I am going to take it away and test it away from the circuit is that still ok ?