Opto pass through

[urthegman]

Hello all, After putting one of my Expresses in its case and attaching a power cord, channel four would light up during the sequential channel test but then flicker when all of the channels flashed. Upon visual inspection, one of the socket pins was not showing through the solder on the bottom. I tried an easy solution of inserting a pin through that spot to see if I could construct some sort of contact point to that leg of the opto. This did not work. I also swapped the chip out with a working one and that didn't work either. So I removed the socket and discovered my suspicion to be true, one of the pins was bent under the socket. Here is my dilemma, when re-inserting the socket I noticed the metallic top ring of one of the pass throughs was missing. (my camera is not working otherwise I would have included a picture) Is there anything I can do to ensure contact with the trace when I put the socket back in? Thanks for any help you can give, George

[JerryPlak]

maybe from this link You are not allowed to view links. Register or Login photo tell tell us what IC # and pin # then maybe someone tell you 

[n1ist]

If the missing pad is on pins 3 or 5, don't worry; those pins are not used.  If it is pin 2, be careful inserting the socket so that the solder-side pad is not damaged, and solder it on the bottom.  If the bottom side trace on pin 2 is damaged, solder a jumper wire between pin 2 and the green LED next to the opto, replacing the trace.
If the damage is to pads 1, 4, or 6 on the top, the easiest way to deal with that is to carefully scrape off the solder mask on the trace where it connected to the pad, bend the socket's pin so it sticks straight out the side of the socket, and solder it to the scraped-off section of trace.

/mike
 

[urthegman]

Sorry, It is the one for channel four and of course it is the one on top of the board right next to the trace that leads to the triac. In the picture it is the on the bottom of the fourth opto all the way to the right.

[urthegman]

If the missing pad is on pins 3 or 5, don't worry; those pins are not used.  If it is pin 2, be careful inserting the socket so that the solder-side pad is not damaged, and solder it on the bottom.  If the bottom side trace on pin 2 is damaged, solder a jumper wire between pin 2 and the green LED next to the opto, replacing the trace.
If the damage is to pads 1, 4, or 6 on the top, the easiest way to deal with that is to carefully scrape off the solder mask on the trace where it connected to the pad, bend the socket's pin so it sticks straight out the side of the socket, and solder it to the scraped-off section of trace.

/mike

I'm not sure how the pin counts go, based on the picture is this schematic correct?       5   3   1
                                                                                                                             
                                                                                                                             6   4   2

[chrisatpsu]

3 2 1
4 5 6

[urthegman]

Thank you everyone, glad I was patient with this,that is what I love about this place, since it is pin 6, I NEVER would have thought of carefully scraping off the solder mask and soldering the pin to the trace on my own!!! I thought I would be running to Radio Shack for some kind of tape that might bridge the connection somehow, this solution saves me a trip and is much easier! I'll let you know how it works out.

[urthegman]

Ok, I got the socket back in and after scraping enough of the solder mask off to create contact I was able to solder pin 6 on the socket to the trace leading to the triac. I put the opto chip in the right way plugged the Express in and after initially lighting up channel 4 once again started flickering sporadically.    I touched up the solder points for the opto and triacs as well as the one for channel 4 on the pic and tried it again with the same result (flickering sporadically).  I attached a power cord with some lights coming out of channel 4, plugged it in again and the lights flickered but not as frequently as the channel 4 led on the board. I swapped the opto chip but still had the sporadic flickering. Question, if the led was in backwards on the board, would it flicker? Also could it be a bad triac? Should I try the controller with a pic from another controller?

[rm357]

If the led was in backwards, it would stay off.
If you have another pic, I'd try swapping it just because that is easy...

Triacs can do funny and strange things. However, if the led is flickering, the triac is probably ok.

The trace runs like this. +3.3v -> opto -> led -> pic.
It looks like channel 4 goes to pin 6 on the pic, so you should check there and make sure that solder joint is ok and that the pin is not bent under on the pic.

The opto provides isolation between the low voltage and high voltage parts of the circuit. If the led is flickering, the probability of something from the high voltage side leaking back through the opto and causing it is really low.

RM

[RJ]

Sounds like a high resistance connection on the low voltage side. (Pic, Led, Opto) any added resistance to lead to problems here where it is hard for the opto tp trigger reliably so you can get flickering.

RJ

[urthegman]

I tried a different pic and the solder joint on pin 6 looked good but I retouched it anyway and changed the led also with no luck. I am going to order a new socket and replace the one I have in there now and hopefully that will work.

[combustionmark]

You can get a 8 pin socket from Radio Shack, Just snip off the 2 extra pins.
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Good luck

[urthegman]

You can get a 8 pin socket from Radio Shack, Just snip off the 2 extra pins.
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Good luck

Never would have thought of that! And I have a spare eight pin socket! Thanks!

[rm357]

Can you post some pics of your board?

[urthegman]

I will be getting a new camera tonight and should be able to post one then.