One channel staying lit

[mitch09]

I have one channel on my LE that stays lit whether I turn it on our of via test controller hardware in light show pro. When unplug it in it comes on no matter what I do. Any ideas?

Ryan

[rrowan]

Normally either the opt chip or the Triac is bad

The easy thing to do is swap out the opt chip for one that is working and see if that channel starts working.

Or just use that channel for a sign    (kidding)

Rick R.

[tbone321]

There really is no need to "swap" an opto to see if the issue is a bad opto or triac.  If the channel LED is out and the channel is still on it is almost always the triac.  To be sude all you need to do is remove the opto for the stuck channel and if the channel remains on then it is the triac.  If it gies out, then I would put in an opto from another channel to test further but why risk bending or breaking the pins on anther chip if it is not required.

[mitch09]

Well I swapped an opto from the only unused channel I have in another LE and no luck. By the way the led on the board tests fine when testing.

On another note I have another channel out in my mini/mega tree. Channel 1 led lights but nothing out.  Opto ?

I'm going to try checking all my solder connections on the power cords next. Wish me luck. Pulling the LEs completely out of the show does not sound fun

[kgustafson]

mitch09,

Really sounds like a bad TRIAC if your LED lights up, the opto chip did nothing different, and you are still getting a lit channel (the TRIACs tend to fail open).  I have two EXs in this condition that I will repair after the show ends.  I just 'worked around' the failed channels and didn't assign those to anything in my show.  Not sure if you have that luxury.

Kurt

[jnealand]

That channel is for your nightlight for security!!!  LOL.  I had one of those and had to replace the triac.  This seems to be the year for triac failures.  I've already replaced 3 and have 2 more to go.

[sirloinofbeef001]

That channel is for your nightlight for security!!!  LOL.  I had one of those and had to replace the triac.  This seems to be the year for triac failures.  I've already replaced 3 and have 2 more to go.

this is the year of the triac.  Replaced one with two waiting til after this season. More time to unplug the cords and plug it all back up than changing it out..thankful I bought a lot of extras.

[mitch09]

I am not looking forward to changing the triac. Any tips for desoldering or removing the triac? (Channel 7) middle of the board.  Do I need to remove the heatsink?

thanks in advance,

Ryan

[jnealand]

While it can be a pain to do it is best to remove the heatsink and cut off the top part of the triac.  get the radio shack desoldering tool it makes it much easier.  There are lots of threads talking about triac removal that include a link to the radio shack tool. Maybe we can Rick to put a little blurb together to keep in the wiki instead of folks reentering this info all the time.  Hint Hint

[kgustafson]

Okay.  I finally got around to fixing my two bad triacs (one on two different Lynx EX boards). 

Here is what I have in my de-soldering arsenal:  Radio Shack Bulb-type desoldering iron, Desoldering braid, hard metal pick tool (got this in a solder tool kit from the shack), needle-nose pliers, and rosin based flux (also from the shack).

Step one:  Remove the board from the enclosure.

• Remove all connections (power and cords) from the board
• Unscrew the board from the enclosure (make sure to hold on to screws and risers you may have used previously)
• Carefully remove the board (make sure you take appropriate anti-static precautions)

Step two : Remove the heat sink from the PCB

• Unscrew all 16 Triacs from the heatsink.  Take care to save each bolt and locknut in a safe place
• Unscrew the Heat sink from the PCB (two screws).  Take care to save the screws, plastic riser, and plastic washer in a safe place
• Remove the Heat sink taking care not to get any heatsink compound on you or your clothing (that stuff is a mess!)

Step three : Remove bad Triac

• Use gentle force to rock the bad Triac back and forth until the legs snap off.  Be careful not to move any of the neighboring Triacs
• Throw away the old Triac (so you don't confuse it with the new one!)
• Apply a bit of flux around the remaining three 'legs' that are left
• Use either a desoldering iron or desoldering braid to soak up all of the solder as possible. Remember to desolder both sides of the board (the original solder side and the side the triac body was sticking up from).  The idea is to get as much of this clean as humanly possible. Work in 10 second phases to avoid any burning around the pads.
• Use the iron to heat up any residual solder on the leg and use the needle-nose pliers to pull each leg out. If you do this correctly you should have three clean holes where your triac once was (use a light and magnifying glass to check).
• If your holes are partially obstructed by solder, you can either try to remove more solder with the desoldering techniques or use a soldering pick (hard metal pick) to try to enlarge the hole manually.  Keep at it until you can safely and easily push the new triac into place.
• Solder your new Triac in place

Step four : Reassemble the Heat Sink
Step five : Re-attach your PCB to the enclosure and re-attach all cords
Step six : Test to make sure your new Triac works!

[chrisatpsu]

good write up