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Hi, could someone please help? I built my bulbdial clock a year ago and it was working fine. I didn’t use it for a while and when I plugged it back in it seems to have developed a fault. Many pf the green LEDs are now being skipped in testmode, so instead of lighting up one at a time in each of the four corners of the clock, two LEDS are being skipped (so 8 will not light up at all). I have dismantled the clock back down to the green layer and have resoldered all joints, not just the green LEDs but all over the PCB, so the joints to the chip, resistors etc. All joints look good, I see no dry joints and have checked continuity with a multimeter to check there are no shorts. I have also double checked the polarity of all LEDs and all is okay on that front too. I have run out of ideas what else I can check. The green LEDs appear to have no numbers (like the Blue ones) but the ones which do not light are directly above the blue LEDs numbered D24 and D34, D35 and D45, D61 and D12 and finally D13 and D23.
I’d really appreciate it if you have any other tips. Many thanks,
DonnaFirst, I would urge you to be more careful with “resoldering” type work, as it is often possible to cause problems by resoldering or overheating things that don’t need to be soldered.
The 9 LEDs that are affected are (reading out the names from the green green board) D39, D93, D49, D94, D19, D91, D29, and D92. You can see how these are wired up if you refer to the schematic.
The two other LEDs connected to these are D59 and D95, located above D46 and D56, respectively. You may also see an issue present on those two, if you look carefully.
These 10 LEDs are the only 10 connected to the “LED9” signal. The first thing that you should check is the soldering on the “LED9” vertical jumper, and at resistor R9. You might check with your multimeter that there is 24 ohms of resistance between R9 (measured on the green board, or at any of the affected green LEDs) and pin 5 of the microcontroller. (Pin 5 is close to the rectangular outline at J2.)
Carefully inspect the soldering at all 10 of the affected LEDs. If you have the ability to, test the LEDs individually as well. A failure of any of these LEDs — due to overheating during soldering or bending stress — could result in what you’re seeing.
Great; that sounds like excellent progress.
No, that on its own doesn’t have any clear possible cause. Look around further and see if anything else is related.
It is usually much harder to deal with “slight” or intermittent issues, as it may have to do with the performance characteristics of a particular LED, rather than a full missing solder joint or the like.
Do all of the red LEDs work correctly, if you go around the circle? Any stray blue/green lights come on when you do so?
These LED patterns that you’ve just described do not make sense to me. I think either you have mis-identified the LEDs or something is severely wrong.
Blue LED D45 is the one connected from LED4 to LED5. To turn that on, we take LED4 high and and LED5 low.
Red LED D510 is connected from LED5 to LED 10, and red LED D104 is connected from LED10 to LED4. In order to turn on D510 or D104, we would expect to require that LED5 is high and LED4 is low — the opposite of what we’re seeing.
Can you please double check the numbers that you have cited, and — since it sounds like you might have removed a ring — also double check that each board is in the correct orientation– with the “*”s lined up one above each other, and solder joints on all three boards facing up.
I imagine that should be “When Blue D16 is ON, Red 110 and 106 are ON”.
With that correction, those values make reasonable sense.
Can you please double check what power supply you are using, let me know the voltage and current specs, as well as the model number if available.
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