No Horizontal Segments Light – Red Alpha Clock Five

[Lon Larson]

My request is for suggestions about what I should look at for debugging this.

I’ve been assembling a red Alpha Clock Five. I got to the “HELLO WORLD” point in testing it. It looks like it is working correctly, except none of the horizontal segments light. Let me call them H-segs for short. It looks like it would spell HELLO WORLD correctly if the appropriate H-segs were lit. Likewise with the segment test where it goes one by one through all the segments, there is a pause each time a H-seg would be lit with nothing showing.

The only 4 of the 5 LED units have the same date code on them, but they all show the same problem, so I’m thinking a manufacturing defect with the LEDs seems unlikely (but still worth checking).

I am just a hobbyist in electronics, but I am prepared to do some digging, try out things, test things, and basically put in the time and head scratching needed (frequently a big part of learning). But if anyone has some suggestions of likely things to check and look for first, or resources to use (better schematics, datasheets, etc.) I would appreciate it. Thanks.

[Windell Oskay]

Do the decimals light?

[Lon Larson]

I have not seen the decimals light either. I wasn’t sure if they were supposed to in either the “HELLO WORLD” routine, or in the sequential segment lighting, so I didn’t mention it. But no, no decimals have lit.

[Windell Oskay]

The short segments and the decimals are all driven by IC U3. If none of them are lighting, then either U3 is not running or it is not getting the signals.

Check that the chip is oriented properly and fully seated in its socket. In the schematic ( https://bcdn.evilmadscientist.com/source/alphafive/fiveletter_RevC.pdf ) note that U3 has power and ground connections at pins 1 and 16, and receives its serial data with pins 2, 3, and 4. So, check that the soldering is good at each of those pins. Next, check pin 22 of U2, where the serial data comes from.

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