burned out a channel resistor

[patrickj]

I had a problem with channel 7 not working, opened the box and found out the ch7 resistor is burned out. [see pic]

I have 7 sets of Philips/Target LED branches on this channel. Each set has an AC->DC transformer, so 7 transformers total.

120v AC 8W to 12v DC 6W

Besides the inefficiency, is there anything weird about this that could have caused the burn out? Every other channel works perfectly, but every channel also uses straight AC lights.

If the LEDs caused the burnout, is there a more appropriate value resistor?

Or is this just bad luck (either way, have to replace the resistor).


Thanks!


*edit* forgot the pic..

Attached files

[TJ Hvasta]

uh oh... you cant use any LEDs that have its own transformer or controller.. ya just cant.. fading/dimming/shimmering/ or doing anything other than just straight on/off will kill the lights, or the board, in this case, it was the board. you are lucky(so far) it appears just the resistor is fried.. you can replace it with one from Radio Shack. But you cant use those lights. you just cant.. unless you make them just blink on and off, no fancy stuff.. ever.

[BrownOut]

The transformers in this product do not have any voltage regulators- I am using 3 on the side of my house without a problem. Sorry to hear your channel is burnt.

[jeffl]

If this a self built kit? It could be a missed or bad solder joint on the triac and opto (components on both sides). You might be lucky with a new resistor and some solder touch up.

[pyromill]

Looking at this picture it appears a self built kit.. noticed the pads are not flowed through...wave pool solder would be flowed.. just a suggestion but hit that board with some more solder when you replace the resistor. The one burned up is the first to catch my eye as not flowed through... around the triacs , opto's and flip flop also looks some pads were not flowed through.. I'd go through a double look in a lighted mag myself..

[bob_moody]

Good eye Pyromill. I have to agree on the retouch. Of my 10 boards, 7 are kit built. I know on the triacs and on the spade clips it's sometimes hard to get things hot enough for solder to flow without thinking your going to burn up the component, delaminate the solder pad or scorch the board.

I was not aware of the transformer issue. Learn something new everyday. Although, the only LED's we have are the C9 retro's on the roof line. I can't speak intelligently about them.

Patrickj, as mentioned you can get the resitor from Radio Shack. I would be a little hesitant as to the consition of the other components on that channel, but before you fire it back it up (no pun intnended) I would take Pyromill's advice and retouch ALL of your solder joints.

[patrickj]

Hey all - thanks for the advice!

I do remember testing the LED branches at one point when I was getting the software running and not having an issue; on/off/fade, etc. The further along I'm getting with this I don't think the problem was the LED w/ transformer.

First thing, once I replaced the resistor I also reflow'd all of the solder joints. Tried running the channel test with only 1 LED set (rather than the full 7), it burned out again. Smoke, smell, small flame flash, the whole bit - was pretty cool.

I replaced the resistor a 2nd time (ty radio shack for having 5 packs) and tried a dead simple known working incandescent string. It started to burn out again but fortunately I cut it just as it started smoking.

Any recommendations on what to hit next? Would the triac or isolator be the next place to look?

For clarity's sake, the lights did On/Off during testing as they were supposed to. Also, everything else works perfectly. I've been running shows (minus ch 7) since Thanksgiving.


Ideas?


(for testing, I was using the hardware utility to on/off cycle through channels 1-16)

[jeffl]

Take a good picture of the front and back of the PCB and post it. Make sure you take the picture in daylight (a flash is not the same) so it's detail is good and clear.

From that my guess is somebody will be able to see what the problem is.

[Guest guest]

So, assuming the channel did work previously, self-built board or not, your continuing flameout issue would suggest you have another component issue, likely culprit a triac.

Also make sure you have the right value of resistor.

Being that you have replaced the resistor twice, and cooked it both times, I'm going to assume you have checked the board for any obvious damage, arcing, etc. that may have occured the first time it happened. If you've reflowed all the connections, would also doublecheck under a magnifier that you did not accidentally create a new solder short.

Assuming you are 100% AOK there, next thing I'd be looking at is the triac.

[patrickj]

Sorry, wasn't clear in the earlier post - I had tested the transformer LED but don't remember what channel it was on.

I'll get some pics asap, thanks!

[patrickj]

Hey all,

Thanks again for the help! I swapped out the ch7 triac with another that was known working (ch1) and ch7 started working properly, putting the blame on the triac. Just installed the replacement (have an awesome fully stocked electronics shop nearby) and everything is 100%!

Not sure if it was originally a faulty triac or I damaged it from the get go, but all is right with the world now.

Happy xmas!