Bulbdial Kit – Issue with Multiple Blue LEDs

[blentz]

Hey,
I am building my second bulbdial kit, SKU 950. The first one I build went off without a hitch. The second one, being built with my daughter, not so much. We’re currently stuck at step 25 / step 26 – we are having issues getting the blue LEDs to test.

Individually testing each LED, we have the following results:

– Testing D25: D25 does not light, however D24, D15, D45, D65, D26, and D21 all light instead (albeit, dimly)
– Testing D16: D16 does not light, however D14, D15, D26, D46, D56, and D12 all light instead
– Testing D61: D61 does not light, however it occasionally flickers, when off, D62, D63, D64, D65, D21, D31, D41, and D51 light in it’s place
– Testing D13: D13 does not light, however D43, D53, D14, and D15 light instead
– Testing D23: D23 does not light, however D26, D24, D63, and D43 light instead

D36 was removed due to a previous issue and replaced with an extra. That one is working fine now. I would put more spares in but there is an awful lot of these dead.

I am using a 30W soldering iron from Radio Shack. I’m having a tough time believing I’ve cooked so many LEDs putting this together. I am also having a tough time believing that the manufacturing failure rate of these LEDs is 16%.

I have been over the kit about a dozen times heating and reheating each and every last solder joint. The board is free of debris; there are no visible shorts or issues any where. I have removed the individual LEDs that have given an issue and resoldered them, sometimes they flicker a little, other times, nothing. I had absolutely zero issues with the first kit I put together and I never had any of those LEDs die. Both kits assembled using the same tools, same soldering iron with the same wattage.

I’m pretty frustrated. Any help I could get would be greatly appreciated.

– Ben

[Windell Oskay]

The “DOA” failure rate of the actual LEDs is very low– if we were to install 1000 in a panel, we would expect zero failures. However, they can be damaged by overheating or by physical stress.  

Is it possible that your soldering iron tip is not *shiny*? If your tip is not tinned well, that can lead to poor wetting, and may mean that you need to heat the joints for significantly longer than the 1 second (or so) that we recommend. We recommend *never* to reheat/reflow a solder joint unless it is known to need repair. We’ve had a lot of experience helping people get their kits up and running, and from that experience we can say that reheating components and removing parts (not certain to be damaged) are the two most common ways that components and the circuit board itself get damaged.  

You can download the Bulbdial electrical schematic (PDF) from our documentation page: 

http://wiki.evilmadscientist.com/Bulbdial

The relevant part is the LED matrix, visible on the first page of the schematic. From this you might be able to see (for example) that if D16 were damaged or missing, D12, D13, D14, and D15 would be expected to light dimly. However, if there are short circuits or more than one or two damaged components, it can get pretty difficult to identify where the issue is.

In cases like this what we normally do is suggest that you do is to contact customer service directly ( http://shop.evilmadscientist.com/contact ). We can send you some replacement blue LEDs, or sell you a replacement blue board with its components at a significant discount.

[blentz]

Hey Windell,
Thank you for your response.

Before beginning the project, I installed a brand-new, out of box soldering tip, also from Radio Shack, a part number designed specifically for my soldering iron. I tinned it according to the instructions and standard practice, and it was kept clean during assembly using a moistened folded-up paper towel. Not high tech, but it does the job.

Since updating this forum post I have been back to my kit. In manual blue ring testing mode (or whatever it’s called) I was able to signal each of the problem LEDs on with the +/- push buttons and each time I was able to read between 4.5 – 4.9 volts DC at each of the problematic LED leads, polarized in the correct direction. If that’s not enough, I also measured voltage at the resistors that power each LED combination, and found 4.5 – 4.9 volts DC at the resistors as well. Finally, with power removed, I was able to check continuity between the resistors and the leads to the LEDs. In all cases, the solder joints and components supplying power to the LEDs appear to be working properly according to my multimeter.

D25 reads voltage between positive at R2 and negative at R5
D16 reads voltage between positive at R1 and negative at R6
D61 reads voltage between positive at R6 and negative at R1
D13 reads voltage between positive at R1 and negative at R3
D23 reads voltage between positive at R2 and negative at R3

Sorry to differ with your previous experience with other customers, but if I can read 4+ volts at the base leads of the LEDs in the correct polarity, and they do not light, I would have to believe the LEDs are at fault. I suppose there could still be a current delivery issue even if I can read voltage with a voltmeter whereas under the 100-some-odd milliamp load there is an issue, but alas, I digress.

I wish now that I had tested them ahead of time, but I didn’t expect to be left with 5 dead LEDs so early in the assembly process.

I read here and else where the you do not recommend reheating or reflowing a joint – I’m very curious how you propose to repair a cold joint, if not with heat? Not an excessive amount of heat, mind you, but enough to fix the joint? I guess I don’t understand this recommendation. The solder tip is applied for a few mere seconds – again a 30 watt. How do you replace parts if not be reheating and removing them? This advice sounds absolutely bizarre to me.

This second bulbdial kit was a gift. I suppose this isn’t the right forum to address that however with the return/exchange issues and whatnot, I will take it up with customer service if there’s no other avenues to pursue here.

Any chance the exact specifications of the blue LEDS are available? What voltage, forward current and brightness characteristics do they have? I guess I’d like to see if it’s possible to source the replacements elsewhere in case customer service isn’t willing to replace since, this was a gift, it’s been halfway assembled already, and the assumption that the customer has overheated any LEDs that fail to light – becomes an obstacle for me.

[Windell Oskay]

> Sorry to differ with your previous experience with other customers, but if I can read 4+ volts at the base leads of the LEDs in the correct polarity, and they do not light, I would have to believe the LEDs are at fault. 

I did not say (nor intentionally imply) otherwise. I absolutely believe that these LEDs are dead. We have helped hundreds of people build and debug issues their BulbDial kits, and we do know that LEDs do sometimes get damaged in the process. That’s one of the reasons that we’re happy to replace parts when needed. Five getting damaged in the installation is surprising, but _certainly_ not unprecedented. 

I also stand by my statement about the LEDs arriving in good condition. Test, for example, the LEDs in your green and red bags. Test your replacements when they arrive. (And if you do find any dead, we would _definitely_ want to hear about it!)

> I suppose there could still be a current delivery issue even if I can read voltage with a voltmeter whereas under the 100-some-odd milliamp load there is an issue, but alas, I digress. 

I’m not sure where the “100-some-odd milliamp load” part came from. There isn’t anything like that in the kit. Those LEDs are not designed to withstand 100 mA, and can easily be burnt out if you put that much current through them. 

 > I’m very curious how you propose to repair a cold joint, if not with heat? 

I did not propose anything of the sort. What I said is that “We recommend *never* to reheat/reflow a solder joint unless it is known to need repair.” 

Yes, if you do have a known cold solder joint, then reflowing it (well, flowing it for the first time) is the correct way to fix it. But reflowing _every single solder joint_ is one of those few consistent ways that our kits can get “totalled.” (That is, damaged such that it becomes much easier to start over than to repair it, for example by delaminating traces and pads from the circuit board.) 

 > How do you replace parts if not be reheating and removing them? This advice sounds absolutely bizarre to me. 

Again, I suggested nothing of the sort. I suggested that only known-damaged components should be removed.

>I guess I’d like to see if it’s possible to source the replacements elsewhere in case customer service isn’t willing[…]

I am the person that designed the Bulbdial kit, and one of the two people that do our tech support and customer service. We’ve already both talked about it and _are_ willing to send you replacement blue LEDs and/or sell you a blue ring with parts at a significant discount if you’d like to start over (most people at this stage prefer that direction). However, you’ll still have to contact us by e-mail or contact form, because our forums are not a good place to discuss things like e-mail and shipping addresses, and so forth. 

As far as sourcing elsewhere, you certainly can look up the specs, but we would strongly recommend using parts from the very same LED batch for a reasonable color, intensity, and angle matching.  (Ideally, just let us send you the replacement parts, so you can get up and running again, and have a nicely matched clock).

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