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Channels 1-8 not working


Tim Fischer
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Hi all,

I just sent this to LOR kit support, but if anyone here has any ideas, I'm open!

I recently assembled a CTB16PCK kit. This is my first LOR controller that I've built "from scratch". Problem is, I'm having issues with the left bank (Channels 1-8). The right bank seems to work just fine.

I checked the following from the kit troubleshooting doc:
1) Left half of board is powered. Triacs show 120V between center pin and neutral.
2) Fuse is good (see above)
3) U4 is properly oriented, no pins folded under. I 'touched up' the solder joints here to no avail.
4) R15 & R16 seem fine.
5) Solder joints seem fine, although it's really hard to tell with such small holes.
6) U2 might be my problem... I installed it backwards the first time (never powered it up that way) and had to pull it and reinsert it -- some pins got bent. I straightened them and it seems to be fine in its socket, but maybe something isn't making proper contact?



What I'm really looking for is someone to say "measure this at resistor x" or "make sure blah blah blah measures as follows..." so I can trace what in the world I did wrong...

I have a multimeter and digital logic probe at my disposal...

Thanks!

-Tim

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Yeah, that's the troubleshooting doc I mentioned, but thanks for the help.

I'm open to any other ideas -- would like to get this this puppy working! :)

-Tim

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Tim

Are you powering this board with 2 power input cords?

If not then you will need to put jumpers in. The jumper locations are marked on the board. Also, if only using one power input cord you only need one fuse.

Chuck

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Jumpers are in to power both sides of the board from one cord (at least for now -- I may put in dual cords for the final enclosure).

There is 120V of power from the triac's center pins (on both sides of the board) to neutral.

Thanks, and keep the thoughts coming...

-Tim

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Just heard back from Dan -- he's thinking that the issue is either with U2 (the micro) or U4. Evidently there are 8 shared data lines between U4 and U5 (controlling the 2 halves of the board) and those must be working since my 9-16 are working. There's an additional "data latch line' for each chip, and that's sounding like the suspect. Or I suppose it could be power/ground to U4 as well...

I'll be checking that out when I get a chance (I'm at work now...)

Not sure what pins this latch line is on, but hopefully I'll figure it out... :)

-Tim

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if you have another pc board - Try swapping U2

This will narrow it down. I have already sent one board in to LOR and it had a bad U2 chip.

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Dr. Jones wrote:

if you have another pc board - Try swapping U2

This will narrow it down. I have already sent one board in to LOR and it had a bad U2 chip.


I don't have another PC board, unfortunately. Dan gave me some more details on the pinouts and voltages to look for and I'll be trying that when I get a chance (have been gone all day, just got back home about 20 minutes ago...)

-Tim
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OK, once again I proved I'm an idiot :(.

Evidently in my haste in assembling the kit, I didn't notice that channels 1-8 have their optos installed upside-down compared to channels 9-16. So I now have 8 channels with the opto's installed backwards...

So, a couple questions (I've already emailed Dan as well):

1) Did I smoke 8 triacs? Or should they be ok, provided I can switch them around? (Looking at the MOC3020 datasheet, I see both sides have a N/C pin so I'm hoping??)

2) Any tips on how best to desolder these pups? I don't think I've ever desoldered an IC and had it live to tell about it... I guess depending on the answer to #1, it may not matter...

This is why I should just buy stuff premade :P.

-Tim

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I have a desoldering iron and a solder sucker. I just ordered a spool of desoldering braid off of ebay as well. So I should have my options covered :P

The problem I've always had with DIPs is that it's hard to get all of the solder off of all the legs, and you can't heat up all the pins easilly to get the dip to slide out... But with 6 pins maybe I have a prayer of getting it to work (heaven forbid I'd have to desolder and reinsert a U4/U5 or U2 chip :(

-Tim

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Well, I swapped one of the optos around -- it now works fine. Only 7 more to go.

Dan also emailed me afterward and confirmed they should have survived the mistake...

To make matters even more fun, I knocked my desoldering iron off the stand and it fell and burned a hole in my office carpet :dude:. This is going to be one expensive kit :P.

-Tim

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Tim,

I also did this on one of my kits, but only one opto! After that, I put a little black mark on the opto as I kept confusing myself with the little sumbol vs. the dot. I use that compressed air in a can to desolder. Just watch where you do it, blows the solder quite well!

I don't think you smoked the triacs.

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Well after a couple more missteps that I won't get into here (too embarassing :) ) I got the remaining 7 opto's desoldered last night. I only broke off one pin, and fortunately it was in a position that I could make the connection to the neighboring resistor that it's supposed to connect to with a small solder bridge. I ran out of time (worked until about 1am!-- but then I didn't start until about 11:45...) and will have to solder them back in and test another night (maybe tonight).

Things should work assuming I didn't fry them while desoldering...

It will be nice to have this kit finished, finally.

Lesson to all: When building the kits, FOLLOW THE INSTRUCTIONS TO THE LETTER AND DON'T MAKE ANY ASSUMPTIONS! It's taken me about as long to 'fix' the kit as it did to build it the first time!

-Tim

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Finished it up tonight, up through installing the heavy-duty heat sinks. Works like a charm!

So this saga ends, I hope! Now onto building it into an enclosure...

Thanks all for the help, and especially thanks for Dan for the extremely prompt and detailed debugging assistance!

-Tim

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  • 2 weeks later...

Well, we'll get to see how well my desoldering skills are. I built 4 PC kits this past weekend and last night I tested them. One didn't work and when I looked at it, I had the notch on the wrong side of both U4 and U5. Desoldering two 20 pin ICs isn't my idea of how to spend a weekend, but I think it can be done with the right tools and a whole lot of patience.

Although I have a desoldering vacuum thing, I think for this one I'm going by Radio Shack and getting their combo iron/desoldering bulb. It has the bulb attached to a 40w iron. That, plus braid and a bit of flux should (maybe) make this a successful chore.

If that doesn't work, then the only solution is to cut the legs off the chip, remove the legs from the board, and get two new chips. Personally, I'd rather give desoldering the old college try. I had success doing this quite a few years ago, but it does take some skill.

Next, I'm going to have to brush up on my reading skills. I successfully built 5 kits previously with no problems whatsoever, then all of a sudden do something as stupid as this.

AAARRRGGGHHHH!!!!

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I feel your pain!

I'm almost embarassed to admit it, but I also had installed U2 (the micro) in backwards, but fortunately a) I noticed it before powering up the board, and B) it's in a socket!

Man, if only there were detailed instructions or something telling you which way these things went! :P

-Tim

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Rather than desoldering, just mount the board upside down. That way, the notches will be pointing in the right direction! :P

Maybe it would be easier just to cut all the leads and then remove each lead individually. Then, get two new ICs from Dan; he will replace them free.

We need a "Murphy's Law" forum for our mistakes! When I got my first board, I ordered the assembled 1602, all I had to do was mount it in a box and attach the pigtails. Somehow, I managed to attach two hot leads to channel 9 and cooked the triac when I powered it up.

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Denny wrote:

Maybe it would be easier just to cut all the leads and then remove each lead individually. Then, get two new ICs from Dan; he will replace them free.


I'm sure that would be easier -- but I felt bad intentionally ruining 8 optos and making Dan pay... I figured I'd ruin a few in the process and I'd only replace those, but as it ended up, I only broke one leg off one opto and I was able to make the connection with a solder bridge (it was the one between the high-voltage side of the triac and the resistor to AC-Hot...)

-Tim
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Wow! I desoldered the two 20 pin chips (U4/U5) in less than 20 minutes!

They're already installed in the correct direction (I'm so stupid!) and the board is tested - and works!!

Here's what I did:

At lunch today, I went to Radio Shack and bought a desoldering iron and a tin of paste flux. The desoldering iron is a 45 watt iron that has, instead of a soldering tip, a hollow tip that's attached to a rubber bulb. The deal is that you squeeze the air out of the builb, hold the iron on the soldered connection, heat it up for a few moments, then quickly let go of the bulb. Because the iron is in contact with the connection when the vacuum occurs, it's still in liquid form. And if you'll put the iron's hollow tip flush with the circuit board, most of the air drawn into the bulb will be thru the board, bringing solder from all inside the connection.

While the iron was in contact with the connection (5 sec or so), I would move the wire around a bit, trying to squeeze every bit of solder that I could out of the joint. And after I used the bulb, I'd put the iron over a sheet of aluminum foil to get the solder out of the iron's tip. Works much better (IMO) than the traditional solder s u c k e r.

The idea of the flux is that flux not only pre-cleans a connection immediately prior to soldering, but it also helps tremendously in getting solder to flow. The solder we use is rosin core solder - rosin is the flux inside the solder 'wire'. The rosin has pretty well burned off after a connection has been soldered (that's the brown and black that's on the iron after you use it for a while). So by putting a little rosin paste flux on the connection, it helps the solder to flow from the connection to the desoldering tip.

Now - there's no real way that 100% of the solder has come out. Inside the hole that we put the leads thru in the circuit board is a little metal tube that runs the width of the circuit board. There will be just the tiniest bit of solder left.

So after you get all the solder out that you possibly can, carefully (and I mean CAREFULLY!) take a small screwdriver, place it under one end of the chip, and slowly lift. You might even rock it back and forth a bit to get it to break loose. But it'll come out, 'cause there isn't a whole lot of solder left in there. I also have a curved needle nose pliers that I use to help lift it out.

After it's out, I used desolder braid to remove more solder from the joint, straighten the IC chips pins, place it back in the board (the correct way this time, dummy!), and resolder it.

That's all there is to it, folks .. easy peasy, lemon squeezy. No big deal. It took about the same time it's taken for me to write this as it did to desolder one 20 pin chip.

Dan did suggest that I could also use a can of compressed air, but I prefer the desoldering iron/bulb combo from Radio Shack. It's about $15-$16 or so, and it money well spent.

Dan did kindly offer to fix it for me if I'd send it back, but like Tim, I really didn't want to have Dan have to bear the costs and trouble of my stupidity. So instead of paying shipping charges and waiting a couple of weeks, I spent $20 (desoldering iron and paste flux) and fixed it myself.

So for anyone else that solders their chip in backwards, there is hope. And while most web sites on the internet suggest cutting off the leads and replacing the chip with a new one, I'm here to tell you that it's easy to remove. Just be patient, be gentle, and have the correct tools - and you CAN successfully remove a direct solder IC chip.

Mike Maness

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Congrats!

I have that exact same desoldering iron -- bought it when I was probably 13 or 14 for model railroad use. Mine's a bit worse for the wear, though, and wasn't working that well for me. I think it might be clogged up inside... I should probably just invest in a new one someday.

Definitely works well wen it's working like it should, though... With the "solder suckers", the solder always seems to firm up the instant you remove the iron, and it always takes me a few seconds to position the vacuum tip properly and by then it's too late to get all the solder...

As I noted above, I did purchase desoldering braid, but I was impatient and did my desoldering before it arrived. But now I have it in my bag of tricks to try for my next screwup ;)

-Tim

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