Dissecting a Cree LED Incandecent Bulb Replacement

[Madebymonkeys]

No, 288 volts would be way too high for 20 LED's in series.    BTW I was an active member of one of the forums mentioned above for many years.   Unless that 288 volts drops a lot under load it's way too high.   LED's like these on average need around 4 volts.  So about 80 volts if in series.    Cree makes the LED's but most likely the electronics were done in China and may not be the best quality.   Did you see a bright flash before this went out - most likely with a bluish tint?   You can test the LED's with a meter or put around 4 volts across one but most likely they are toast along with the electronics.   
    Just guessing here but after looking at the picture I think this may have been setup as 5 groups of 4 LED's in series so it's more likely to have been fed by around 16 volts when it was working correctly.  The idea of putting all 20 led's in series would not be a very smart design since if one went out the whole light goes out whereas if one goes out with 5 groups of 4 then you only lose 20% brightness.

Series requires only one current limiting component, parallel requires lots.
More volts at lower current (series) is easier than lower voltage at higher current (parallel).
The last decent Philips LED I used had a Vf of 68V. What looks like a single led can typically have multiple die bonded to each other and a metal substrate to get rid of the heat more effectively (when bonded to a larger sink!).

I agree, parallel would eliminate a total failure to product light if a led failed but there are more things to consider ie cost. Design choices always have cost in mind....it's why your TV doesn't cost £50k - it could, but it was designed to a price point.

[mondrasek]

Again, contact Cree and let us know their response.

I used the Cree website contact form to explain about the two bulb failures and offer to provide one for them to analyze should they want to do so.  One week later and absolutely no response.

[Madebymonkeys]

I used the Cree website contact form to explain about the two bulb failures and offer to provide one for them to analyze should they want to do so.  One week later and absolutely no response.

The failure rate, of that product over its sales, is probably within acceptable limits and they wouldn't learn anything new. Nothing will last forever, failures are always expected and numbers calculated.
An email from them would at least be nice though :-)

[mondrasek]

An email from them would at least be nice though :-)

Especially since they advertise these bulbs with a 10 year warranty!  But then again I have received many replacement parts and items from other manufacturers after sending in an Internet claim without ever receiving even an auto-reply.  So I still wait patiently...

But I see no reason why even an auto-reply, as cold as they are, is not considered the minimum responce for such an organization.

[Madebymonkeys]

Especially since they advertise these bulbs with a 10 year warranty!  But then again I have received many replacement parts and items from other manufacturers after sending in an Internet claim without ever receiving even an auto-reply.  So I still wait patiently...

But I see no reason why even an auto-reply, as cold as they are, is not considered the minimum responce for such an organization.

If it's under warranty then a replacement, in theory, should come...although they may question its failure mode if you've already dismantled it