Newly assembled Spiffed Kit, Backlight but No Display

[osme]

Well I got the spiffie kit with the Newhaven blue LCD. I put it together tonight and something's wrong.

Plugging it into the computer, the backlight is on but there's no text. Pressing the middle button doesn't do anything. I checked continuity across the LCD connections and they're fine.

First I thought maybe it didn't have the software, so I uploaded the latest code and it was successful.

I'm suspicious of the quality of my soldering, but I don't know how to desolder the LCD to get to it. I thought they all looked fine before I put the LCD on, but I guess I was wrong.

Does anyone have any advice/suggestions?

[skelly]

Originally Posted by osme

Well I got the spiffie kit with the Newhaven blue LCD. I put it together tonight and something's wrong.

Plugging it into the computer, the backlight is on but there's no text. Pressing the middle button doesn't do anything. I checked continuity across the LCD connections and they're fine.

First I thought maybe it didn't have the software, so I uploaded the latest code and it was successful.

I'm suspicious of the quality of my soldering, but I don't know how to desolder the LCD to get to it. I thought they all looked fine before I put the LCD on, but I guess I was wrong.

Does anyone have any advice/suggestions?

One thing you could do without desoldering the LCD is checking and confirming the orientation of EVERYTHING. Especially the diodes. Be absolutely sure that you have them all installed in the correct orientation.

Secondly, from the component side, you could check to see if you have solder 'sucked' up from the solder side onto the component side. You *should* see that solder was to a small extent wicked up from the solder side onto the component side.

It would not hurt to re-heat some of the leads on the component side if you are concerned about some of the joints.

Also, even though you have tried to adjust the contrast, try tipping the LCD at an angle relative to your eye, to see if you can see *anything* on the screen at all.

[osme]

I triple checked and everything's in the right orientation. Looking at the screen from any angle, there's definitely nothing but backlight.

Most of the joints on the component side have a bit of solder sucked through the hole, but not all. Is that a problem? Should I add a touch of solder on the component side for these joints?

I re-heated all of the leads that I could get to on the component side.

I put a piece of folded thin cardboard between the LCD and the guino board to make sure nothing was touching.

I noticed that the LCD solders on the guino board weren't the best, so I cleaned them up, made them all concave and they now completely cover the metal ring around the hole. I checked continuity between the unused pads on the bottom of the LCD to the solder joints on the component side and they're all good, less than 1 ohm.

There's still nothing on the display. What's the next step?

[dcb]

look at the schematic and map out the lcd pins to the cpu pins and check conductivity on each lcd pin to the cpu. Also check for 5 volts at lcd #2 and that lcd #1 is connected to ground.

Also look for conductivity between lcd pins that shouldn't be there

[osme]

4 problems I've now spotted after verifying with the schematic:

1) Digital Pin 2 isn't connected. There's no continuity between digital pins 2 & 3 or between 2 and the zener. There's a little bit of the pad not covered by the cpu's socket, and there's no continuity between that and digital pin 2 either. I assume it's a bad solder joint.

2) Same thing with Digital Pin 8 to LCD pin 12.

3) No connection between Digital Pin 7 and LCD pin 11. The socket solder is good, but the LCD solder isn't covering the whole ring.

4) I don't get 5V where the schematic says, I get 4.3V. The laptop's USB ports give 5.05V and I've never had an issue with USB power.

For issues 1 & 2, I think I'm going to try to jumper the CPU pin directly to where they're supposed to go. How can I connect the CPU pin to a jumper? If I have hot solder on the jumper wire and touch it to the CPU pin while it's still hot will that work? I'm assuming if I heat up the CPU pin directly, it will cause damage.

Issue 3, I'll fix the solder and hopefully that resolves it.

Issue 4, I don't know. Any ideas?

[dcb]

re #4, Fix your known problems first Can probably solder from the component side w/care.

For cpu jumpers, I usually tin then flatten (i.e. with a hammer) the end of a small piece of solid wire and shove it in the same socket as the pin.

[osme]

I have display!

But that's uncovered another problem, there's a row missing.

I touched up all of the LCD solders on both sides and they all look pretty much ideal to me, all have continuity... What's next?

[dcb]

Sweet I don't think the missing line is a fixable thing, had one do that to me during my earlier experiments. I don't have any way of knowing if it came that way or if it had just been through too much. You can try to bug Spiffie for a new one maybe, but then you have to uninstall/desolder this lcd and install the new one which has many opportunities for error.

This is part of the reason why I test mine after building them and before shipping.

[moorecomp]

Mine did this to me when I disassembled it to invert the polarization mask. There are conductive rubber like strips on the top and bottom edges of the LCD, under the metal mask. You can use a small pick or screwdriver to prod the strip and see if it fixes the problem. A bad connection from the LCD PCB to the LCD glass, through the conductive strip will cause this problem.

Best regards,

Craig Moore

[McTimson]

Mine did that as well on the first one I built, except it was a vertical line, not a horizontal one, so it wasn't as bad. And it also happened after I tried messing with the polarizing film. I never bothered to fix it, as I had another one coming anyway, but it does sound like it was a bad connection somewhere in there.