What's the best way to replace a triac

[UncleBuck]

I have a channel that stays 50% on all the time. I took out the blow dryer and blew everything dry (it really wasn't very damp). So I believe it's the triac. Now what is the best way to replace it? Do I need to remove all the cords and pull it completely out of the enclosure or can I just unscrew it from it's mounts and gently flip it over to access the bottom solder joints. I'm looking for the easiest way but I also don't want to damage anything else.

[duane.mosley]

I have a channel that stays 50% on all the time. I took out the blow dryer and blew everything dry (it really wasn't very damp). So I believe it's the triac. Now what is the best way to replace it? Do I need to remove all the cords and pull it completely out of the enclosure or can I just unscrew it from it's mounts and gently flip it over to access the bottom solder joints. I'm looking for the easiest way but I also don't want to damage anything else.

you should be able to just unscrew it from it's mounts and flip it around. no need to remove all the cords.

[chrisatpsu]

a quick and easy test before you replace a triac would be to swap the opto with another channel to see if that clears up the issue, it remains the same, or follows the opto.

[jnealand]

I have done it both ways.  Taking all the cords off is too much work, but it is awkward leaving them on.  You need some way to hold the board flipped over since the cords tend to try to make it go back into the case and the case is still in the way as well, so make sure you have plenty of room on your workbench.

[UncleBuck]

I did change the opto and it works fine. Do I need to remove the opto before I start to heat up the triac?

[Night Owl]

What I have done is unscrewed the board and flip it.  I unscrew the triac from the heat sink and use a pair of flush cutters to cut the legs off the triac.  Once the triac body is out of the way, it's easier to unsolder and remove each of the legs.     

[jnealand]

I did change the opto and it works fine. Do I need to remove the opto before I start to heat up the triac?

If it works fine after switching the opto why are you replacing the triac?

[chrisatpsu]

i think he meant the opto is working fine.

[UncleBuck]

Yes, the opto is working fine. I'm pretty sure I messed up the channel for good. In my attempt to remove the triac I believe I screwed up one of the traces and still have not been able to get the last triac leg out.  I think I will just live with it until next year. 

[shaunkad]

You can always run a jumper wire if you messed up a trace

[UncleBuck]

OK, I fixed my dead channel by replacing the opto. It was not one of the two channels that do not shut off and stay dim. My question is the channels that stay dim could it also be opto causing the problem?

[Night Owl]

I don't understand.  Your first post says you have a channel that is stuck on at 50% brightness.  Then you swapped an optocoupler and said the optocoupler works fine.  I assume this to mean you swapped the optocoupler with another channel but the channel that is stuck at 50% remains stuck.  Now you say that you fixed your dead channel by replacing the optocoupler.  Which is not one of the two channels that stay dim.

Do you have multiple problems with this unit?  Sounds like you had one dead channel (and by dead I mean not responding to any commands at all) and two channels that are stuck at 50%.  Is  this right?

[UncleBuck]

Sorry for the confusion, I have three problems with three separate LE's. Two of the LE's have a single channel that do not turn all the way off. They work fine other then when they are to be all off they stay lit at about 50%. The third LE had one channel that was not responding at all and by changing out the optocoupler it fixed the problem. So I still have two separate LE's with dimming problem.

[caretaker]

Sounds like your TRIACs are leaking. First test remove the OPTO from the affected channel and see if it goes off. If it does the OPTO is sending voltage to the triac, so try another known good opto. If the results are the same then check for solder bridges or moisture. Now if you removed the opto and the channel stayed on then the triac is most likely leaking and needs replacing. Before replacing make sure the board is dry as moisture can cause the triac to stay on.  One other thing to check is depending on what load you have on the "BAD" channels try putting a 100 watt light bulb on the channel and see if it goes out. If that works you can add extra load to that channel till after your show is done and replace it later.

[UncleBuck]

Thanks Jeff, I switched out the optocoupler and still no go. At this point I'm pretty sure it's the triac that is leaking. I have a 100 count of incandescent mini's on that channel which is part of an arch. I'm shutting the show down after New Years so I will just have to live with it until then.

Thanks for all the help everyone!