Ice tube clock help - top display row not working

[Ric]

Hello and Merry Christmas to everyone.

To cut to the chase, the entire row across the top of the display does not work (see attached pictures). I spent hours trying to debug/diagnose/check/redo solders, with no luck.

I have the 19 pin tube. One of the first things i noticed when I opened the kit was the tube had a burn mark on the glass and a section of it was covered in white on the back (see attached picture). I know that Adafruit tests the tubes before they were sent out, so I wasn't too concerned that the tube might not work (it just wouldn't look as pretty, unfortunately).

The two tube pins at the 'bottom' of the header are as far back as I can trace a problem. While all the other pins have several volts going thru them, these two only have about 3 and 5 millivolts, respectively. i've attached a picture, pointing them out. I know the solder job looks like a mess now, because i've gone back a few times resoldering, trying to fix it, but I don't think it's a solder issue.

Thanks for the help in advance.

[adafruit_support_bill]

The solder on the tube-daughter board looks OK. Can you post photos of the main board?

[Ric]

Here are more pictures. Thx.

[adafruit_support_bill]

The top row would be the 'A' segment. This is pin 19 on JP1 and pin 3 on the MAX6921 chip. Check for continuity there.
Sometimes it is difficult to tell from a photo, but you might have some cold-solder joints. Touch up anything that is not shiny or has not flowed well onto both pin & pad.
There are a couple of pins of the MAX6921 socket that look like they need a little more solder - as does one end of diode D5.

[Ric]

Thanks again for the help.

Assuming I have the right pin (see photo), JP1 pin 19 seems to be fine. I can follow the voltage all the way into the wire from the tube, and depending on which numbers are being displayed, is showing 13.5-16.5 volts. In case I have the wrong pin, what I think is Pin 20 (it would then be the real Pin 19) is 16.5-20.5 volts. As the minutes and seconds change would cause the top row to change, I can see the small fluctuations in the voltage.

All the other pins in JP1 (followed thru to JP2/smaller PCB/VFD tube wires) have voltage as well (minus the two ground pins 11 and 12).


Any ideas?

[pstemari]

One end of D5 appears to be bent over and potentially shorting out against the ground plane.

[Ric]

Thanks for the reply, Paul.

It's actually not touching- just the angle of the picture.

And, even if it was, would all, but the top, horizontal row, work?

I'm starting to go crazy here, as all the wires into the VFD tube (with the exception of the ground) are getting voltage, and even acting like it should be changing the display (the fluctuations in voltage), it's just that the display isn't actually lighting up on the top row.

[Ric]

I was hoping for some more input, but it's pointless now- i've managed to burn out the board trying to resolder for the 10th time the same points that seemed to be fine

[adafruit_support_bill]

If you can hang on a little longer, Lady Ada will be back from vacation next week and may have some other ideas on what to try.

[Ric]

I'm the impatient type and kept tinkering with it until i broke it. I no longer get a beep when i plug it in, no do i have any substantial voltage getting to the VFD now.

I'm also the stubborn type and will have to order new parts. I'm going to get this @#$@%$#@ thing working!

Thanks again for the input.

[Ric]

Hello,

So the new kit showed up and it assembled just fine...everything works great. So i took the old VFD and tried it on the new one with the same problem- Top display row does not work. Since I have voltage going into all the wires that go directly into the tube (minus the ground), I can only assume that it's a faulty tube?

[adafruit_support_bill]

So the new kit showed up and it assembled just fine...everything works great.

Great!

So i took the old VFD and tried it on the new one with the same problem- Top display row does not work. Since I have voltage going into all the wires that go directly into the tube (minus the ground), I can only assume that it's a faulty tube?

That is sounding more likely. Although Adafruit does test each tube before shipping.

There is one more thing you should try: There is an excess of flux residue on the back of the smaller board. Some of it looks pretty burnt. Burnt flux in particular can be conductive and should be cleaned off. Give it a good scrubbing with isopropyl alchohol and an old toothbrush.

[Ric]

Thanks for the response!

Yeah, the burnt flux happened after I went on the resoldering rampage trying to figure out what the problem was.

I just cleaned off the flux thoroughly, and still no luck with the top row.

[adafruit_support_bill]

You can contact support@adafruit.com about a replacement tube. Reference this thread in your message.