Help with green LEDs being skipped

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  • #28106
    DC
    Participant

    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,
    Donna

    • This topic was modified 6 months, 1 week ago by DC.
    #28108
    Windell Oskay
    Keymaster

    First, 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.

    #28130
    DC
    Participant

    Hi Windell,

    Thanks so much for the speedy response and the advice. I have just one afternoon a week to work on my electronics projects, hence the delay in my reply… so I’ll investigate further tomorrow and let you know how I progress.

    I really appreciate the information and the support.
    All the best from Europe,
    Donna

    #28134
    DC
    Participant

    Hi Windell,

    Great news, I’ve finally had the chance to sit down with my clock again and I identified the fault… between R9 and pin 5 I could not read any resistance so was worried about an open circuit although I’m not sure I really understand this measurement because the resistor is already wired into the circuit so wouldn’t I just be measuring the rest of the circuit anyway?

    So, on further investigation and in looking at the circuit diagram, I saw one end of R9 connects directly to the LED9 jumper… however, if I measured for continuity I found none between that end of R9 and the jumper… An open circuit between R9 and jumper LED9 (on the PCB itself!). The PCB looks good visually, so this is strange.

    But anyway, I wired R9 and LED9 up directly using a banana connector and when I do this, the clock works fine. In this case, I guess I’ll just solder a small jumper wire into the back of the blue PCB to connect these two points up.

    Again, unfortunately, I have to leave my reassembly until next Thursday but I’ll confirm if this has solved all the issues next week.

    Thanks for your assistance, much appreciated!!!
    Donna

    #28136
    Windell Oskay
    Keymaster

    Great; that sounds like excellent progress.

    #28137
    DC
    Participant

    Hi again Windell,

    My green ring is working again correctly but upon testing I notice a slight flickering on LEDs D92 and D48. Any ideas what might be causing this? All other LEDs are fine.

    Many thanks again for your assistance,
    Donna

    #28138
    Windell Oskay
    Keymaster

    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.

    #28139
    DC
    Participant

    Hi again Windell,

    I’m working overtime on my clock at the moment. The blue and green ring were working great so I reattached the red ring. Upon alignment the red ring is working great too.

    However, now that the red ring is attached, when three of the blue LEDs light up, two of the red leds are simultaneously on:

    When Blue D45 is ON, Red D510 and D104 are ON
    When Blue D16 is ON, Red 101 and 610 are ON
    When Blue 42 is ON, Red D210 and Red D104 are ON

    :-(

    Any idea what’s going on? I thought I’d finished the fault finding but now this! The Blue ring worked great before attaching the red layer.

    Cheers again for sharing your insights.
    Donna

    #28142
    Windell Oskay
    Keymaster

    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?

    #28143
    DC
    Participant

    The red dial LEDs all work great, not a twinkle from any of the other (blue) LEDs when each of them is on…

    #28144
    Windell Oskay
    Keymaster

    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.

    #28145
    DC
    Participant

    You’re right, this doesn’t make sense. I just double checked the LED numbers and you were correct, I had read these the wrong way around… here’s what we actually have:

    When Blue D45 is ON, Red D410 and D105 are ON
    When Blue D16 is ON, Red 111 and 106 are ON
    When Blue 42 is ON, Red D102 and Red D410 are ON

    Do you know from this what’s going wrong?

    Thanks so very much for your patience with this (and me!)

    #28146
    Windell Oskay
    Keymaster

    I imagine that should be “When Blue D16 is ON, Red 110 and 106 are ON”.

    #28147
    Windell Oskay
    Keymaster

    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.

    #28148
    DC
    Participant

    The power supply cable supplied with the clock (purchased from Jameco Electronics in the US) is model FY0501000 with US connector:

    input 100-240VAC 50/60Hz
    Output 5VDC 1A

    I’m in Europe on a 230V and 50Hz mains voltage, using a travel adapter.

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