Hello,

I just bought two Meggy Jr RGB's for my two sons. One of my son's just finished working on his board (Soldering). When he was done we checked his soldering. All looked well as far as nothing being overlapped. The meggy Jr RGB turned on and withing a half of a minute it turned off and we were never able to turn it back on. When it did come majority of the LED board came on along with the upper LED's. We check continuity on the each component to rule out burning out a component. We found that two of our Capacitors in the right hand corner did not seeme to have continuity. Can someone help us with this problem? We would like to get it working before Chirstmas.

Sean

The most likely issue that could cause this kind of thing is a bad solder connection somewhere that broke while being handled.

You should very carefully check all of the solder connections on the board-- particularly at the battery wire, near the oscillator crystal, and near the chip --to look for any connections that are broken, missing, or look "dry" like they could have cracked. Good solder joints should look shiny and wet, like a drop of liquid silver.

Capacitors should *never* "have continuity" -- if they do, something has gone very wrong. (And, it's usually impossible to test a resistor or capacitor while embedded within a circuit.) Can you please say what equipment you are using to check for continuity? If you have a multimeter, there are several things that you can check.

Sure and thank you for your reply because we are pretty new to this. I used our Multimeter to check continuity.

We have gone over the Solder but we will look at them again with your advise in mind. Im pretty sure there are some that need attention.

Ok we checked all of our solders and re-soldered what we thought was a cold solder. Now the Meggy Jr RGB comes on but not all of the LEDs come on in the big screen. Rows 1,2,4, and 5 are not working and sometimes during the middle of the game the game stops, then starts playing again with no sound.

It seems to crash alot during play, never getting through a whole phase or sequence. After that the noise turns off. I have to keep resetting it to come back on.

What battery voltage are you seeing?

It's most likely that there's a flaky connection affecting power, or possibly the oscillator. You should see very close to 4.5 V at the chip, on pin 1, for example.

Ok I think we have the off and on thing, I think the oscillator was not connected properly. Why have I lost sound completely now and also Rows 1,2, 4, and 5 of the LED matrix display are not working?

We are new to checking voltage. Can you tell us how to check it with our Multimeter properly.

Ok I think we have the off and on thing, I think the oscillator was not connected properly. Why have I lost sound completely now and also Rows 1,2, 4, and 5 of the LED matrix display are not working?

Great. If there was a bad connection at one place, there are likely bad connections at other places. Try and learn to identify good and bad solder joints visually, so you can figure out which joints need fresh solder. One good graphic is figure 3, from here:
http://www.dummies.com/how-to/content/soldering-101.html

The connections between the microcontroller and the LED driver chips are OK, but the connections from the LED driver chips to the LED matrix are not OK. Check the soldering of the LED driver pins-- if you already applied the velcro, pull it back partway to reveal the pins. Then, check the soldering of the LED matrix sockets. There are likely a few bad connections there.

For the sound, check resistors R3, RB8, transistor Q8, the speaker L1, and pin 15 (lower left pin, with board right side up) of the microcontroller.

We are new to checking voltage. Can you tell us how to check it with our Multimeter properly.

Likely no need, since you've fixed the power issue.

Well we desoldered the LED chips and re-soldered them again and the we are still getting the same problem with our LED display. As far as the sound, we did the same. It must be either the Resistor or the transistor, I give up. I think we will have to buy another Meggy JR RGB. I will say that this was tough for my beginnners.

Sean

Having seen a picture of the board this week, I'm not surprised that you're having trouble-- it looks as though the solder simply hasn't flowed to where it has to, leaving evidence in the form of large blobs on the surface in many places.

I don't know why you would have desoldered the chips-- that's not where the problem is. (Nor is it with your resistors or transistors...) And, arbitrarily desoldering parts is the number one way to end up with a kit that really doesn't work. I'll tell you right now where the problems are: In the solder connections between the parts. The issues that you have described are very common, very fixable ones, but you be able to look at the joints and tell which ones are good and bad by appearance.

There is likely something wrong with your soldering equipment or technique that is the root cause. It is also likely easy to fix this root cause, so that you can get your Meggies working. (I don't suggest that you just go out and get a new one. If you can't fix the cause of the problem, you will probably end up with the same situation next time.)

First: Is your iron getting hot enough? Is it tinned? If you're using a type like a "coldheat" iron (or any iron under 25 W), you should expect that soldering will never work well-- it just wont get and stay hot enough. If your iron is good, the solder should *always* melt in less than 1/2 second after touching the tip to the solder. If it has been a historically good iron, check the tip appearance: it needs to be *shiny* in order to work. If it is not-- if it looks dull -- it either isn't hot enough, or it needs to be tinned. Try wiping off the tip (quickly!) on a wet sponge. If that doesn't make it shiny, try melting fresh solder against the tip and wiping again. If that doesn't help, you may need a new tip on your iron.

Second, what about your technique? Solder for electronics contains a flux, usually a rosin core. The flux is a chemical that, when melted by heat, removes the surface oxides on metals that prevent them from being soldered together. Without flux, soldering just doesn't work. When you melt the solder, this flux melts and then burns away, releasing a small amount of smoke. And, once that smoke goes away, the solder is "spent" -- it no longer acts like solder.

So, if you melt the solder onto the iron and then "carry" it to the joint (what they call "using the soldering iron like a spoon" ) it will never work correctly-- by the time that the solder gets to the joint, all of the flux is gone away. Similarly, if you need to hold the iron to the joint for ten seconds to melt the solder may cause all of the flux to go away before the solder melts and can flow into the joint. In either case, you'll end up with big blobs of solder on the surface that *do not* connect the metal bits below. If you end up with this situation, simply remelting the solder joints will not fix the problem, because they do not have any flux left, so the metal cannot flow into the gaps where it needs to. So, to touch up blobby solder joints, as bad as it sounds, you have to add fresh solder, and work within those first few seconds while the solder is still emitting smoke. That's the only way to get it to flow into the joint. To remove excess solder from the surface, you can try to "pick it up" with the soldering iron, use a solder sucker, or solder wick.

A good solder joint should look shiny and wet, like a drop of mercury, wetted to both surfaces, without any blobby, dry, or cracked aspect to it. A good picture for reference is Figure 3, on this page:
http://www.dummies.com/how-to/content/soldering-101.html

This was our First experience in Soldering, including me. The soldering Iron we are using is a Weller in which this was its first use. So yes you may have seen blobs on our board because this was the first time my son had done this. We I say we resoldered some of our solder i meant that we went our and bought a Solder sucker to get rid of our "Big Blobs", and clean up some errors. We are cleaning our tip after every solder to assure our Soldering tip is remaining shiny as you advised.

Where did you see our pics, because we have only posted up pics on our Google plus page that were our original pics of the board. We have made many many changes since then, which led us from having a non working board to now a working board without sound and 4 row of LEDS.

We are using Solder with the Rosin core but I was not aware of how it work because originally I think were were spoon feeding the solder to its destination, causing it not to adhere to the component. I will review what you have sent us and go over our soldering techniques. Thank you for your advice. The fact is, what should I do at this point. More resoldering or what? Made that mistake already evidently.

Sean

. The fact is, what should I do at this point. More resoldering or what? Made that mistake already evidently.

I would actually recommend more soldering, done with some care. It's desoldering that tends to get people into trouble.

First, double-check that the LED matrix is seated properly in place. The instructions describe how deeply the pins need to fit into the socket. If it is not all the way in place, you are likely to be getting a number of bad connections.

The matrix on the Meggy Jr RGB is sideways-- the label is on the left-hand side, if you recall. So, each horizontal row of the LED matrix actually has a separate "column" control for the red, green, and blue LEDs in that (apparent) row. If four rows are fully not working, that means that there are at least twelve bad connections between the LED driver chips and the LED matrix. Since you've fully resoldered the chips without a change, that very likely means that either the problem is at the LED matrix pins.

So, for soldering, start with the LED matrix socket pins. Go through each one of those individually. Look at each pin. Can you see whether or not it's a good connection? If the joint looks blobby, dry, cracked, or there's a gap-- at all --resolder it, with a bit of fresh solder, making sure that the solder flows into the joint.

You may want to do this with the help of your continuity checker. If you don't have them, grab the Meggy Jr schematic from here: http://wiki.evilmadscience.com/Meggy_Jr_RGB

Check continuity between things that are supposed to be connected there. For example, pin 5 of U2 is "col0:1", and should be connected electrically to pin 16 of the LED matrix (U4), which controls the blue elements of the bottom row.

What is the Voltage on the .1 Uf Capacitors and the 19 pf Capacitors?

Most, but not all, of the 0.1 uF capacitors have 5 V (or 4.5 V, if on batteries) across them, and the 18 pF caps do not have a DC voltage.