resistor burned up

[Tigman009]

hoping you might have some ideas as to what caused this?

[rrowan]

My guess would be a short (solder bridge) or a triac problem

take a picture or two of the other side of the pcb

Rick R.

[n1ist]

My guess would be a bad solder joint at the triac.  In that case, the current that the light draws would go through the opto and that resistor instead  of through the triac.

/mike

[coachers]

 Where's LED 12 & 13 ?

 Did they burn off?

[mschell]

One other comment.  There's entirely too much solder on some of the joints on the component side of the board.  Hopefully, you're soldering the leads on the other side of the board when you are putting the components in.  You need to be sure you're heating both the lead from the component and the metal trace on the circuit board.

[Kwajtony]

Good Observation, I think there was a couple of joints that did not flow completely.  I would reheat all the joints (from the bottom) of the circuit board and watch the solder liquify and recool.  It would help to see a picture of the bottom the circuit board to determine what happened.


Tony "C"

[Tigman009]

Here are some pictures of the back.  I used a red marker around the area of the burned resistor.  Thanks again for the help.  As for the missing LED's I didn't notice them broken off until you did.  bummer

[Kwajtony]

Check for A solder Bridge around the OPTO.

[rm357]

I'm not familiar with that version of the board, but look for a solder bridge on the matching triac as well - if there left lead is shorted to the center one, that could do it...

RM

[RJ]

Does not need to be a bridge it can just be a high resistance joint (cold joint) as this put the load across the resistor and does this. It is a common issue and we use to see it more in the early days with the external SSR's.

RJ

[Tigman009]

Thanks for the help but I have no idea what you all just said. 

[rm357]

Basically if your soldering iron was not hot enough for the solder to flow properly into the joint, it could create a "cold" solder joint - which is just a solder joint that is not making a good electrical connection. Usually good joints are shiny and bad ones have a dull finish, but that is not always the case. I run the temperature way up when soldering big items like the triacs. It's hard to get them hot enough unless you have a really good soldering iron as the center lead is thermaly (and sometimes electrically) bonded to the heat sink...

The other part of RJ's message describes what happens electrically if you have a cold solder joint. Basically the full 120v gets put across the resistor and lets out the magic smoke - man does that stuff stink...  

A solder bridge is when a blob of solder connects two things that should not be connected. These happen if there is excess solder on two joints that are close together... the easy fix is to clean all of the solder off the tip of your iron using a wet sponge while the iron is hot, then touch the iron on the blob. Repeat as needed until the solder separates leaving two separate joints.

RM

[Tigman009]

Thanks for the explanation.