Hey there awesome people,

I have a cheap set of Chinese knock-off film lights that come with inline dimmers.

They have a fuse and a safety cap, but on all three lights after the globes blew, the dimming function no longer worked and the lights were stuck at 100% output all the time (800W). The fuses did blow out as well, but obviously, there is some damage to the dimming part of the circuit since it's now essentially shorted.

Can anyone tell me which is the most likely component to have died? Is it the BTA16 600B Triac, the Tenta MEX 275V 0.22uF Safety Cap or possibly even the zener diode? There are no other components besides a few resistors and a couple of metallized film caps, and no burn marks on the board or components.

Also, is there a way to make it so that a blown globe doesn't mean soldering in replacement parts to the board? Do I need different fuses (currently f54L 250V)? Should my replacement parts be higher spec?

Many thanks

Markus

 

I would say most likely the triac. The zener is more likely a diac and remember they are cheap Chinese knock-offs
SG

 

Thanks mate. Not sure why the triacs blew out on three separate lights when the globes went. Do you think higher spec triacs would solve the issue?

best,
Markus

 

I think better quality dimmers not from China would be better...

 

Thanks mate. Not sure why the triacs blew out on three separate lights when the globes went. Do you think higher spec triacs would solve the issue?

best,
Markus

Probably not, the BTA16 is rated 16 amps. Have you measured the triacs to see if they are shorted? It's possible there's something else defective..
SG

 

Thanks mate. Not sure why the triacs blew out on three separate lights when the globes went. Do you think higher spec triacs would solve the issue?

best,
Markus

Can't remember why - but bulbs tend to go short for a few milliseconds when they blow - its rare luck if the triacs don't fail at that instant.

 

Hi, As you know, the dimmer lights are above 800 watts, I think the problem with the input source is high voltage it is better to reduce it. This site also provides good information.
http://matlabprozhe.com

 

Can't remember why - but bulbs tend to go short for a few milliseconds when they blow - its rare luck if the triacs don't fail at that instant.

There must be a way of overcoming this though, because dimmers on these kind of lights do exist, so it's a solvable problem, though not necessarily in this instance.
I'm not sure what more can be done to protect the triacs if a fast blow fuse and a safety capacitor don't cut it.

Best,

Markus

 

The fact that all failed could point to a voltage surge at your location.
The fuse faster than fast blow is a called a rectifier fuse, these have super fast sweep through when a fault occurs, but cost a little more.
Max.

 

Let's go back to this component you called a "safety cap". Does it have any markings on it or can you see how it's wired in the circuit?
Also would like to know how the globes blew. Was it when you first turned them on? Was the dimmer at max when they blew? That kind of stuff might help figure a solution.
SG

 

First of all, I want to say thanks for the help, I really appreciate it.

The Triac is a BTA16 6008. The safety cap is a Tenta X2 0.22uF 275VAC 40/100/21. The lights all blew at separate times, and the dimmers were all operating at 100%. I believe the globes blowing is because the lamps shipped with poor quality globes.

To be clear, the lights still operate, they just won't dim. Makes me wonder if that isn't typical of an X2 cap failing out to short mode?

In terms of wiring the safety cap seems to be wired between mains and ground. The mains comes into the dimmer box and goes through the fuse and the safety cap before hitting the triac gate. On the way back from the lamp head, the it pretty much hits the triac anode first thing. If the voltage spike comes from the globe failing in the lamp head rather than a mains surge, could reliability be better if there were some kind of protection in the reverse direction?

When I get a moment I think I'll remove them from the circuit and test to see whether the triac or safety cap is shorted, which should give me some idea of which component is the problem.

Thanks

Markus