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HELP - - Replacement mini lights instantly burn out


ggregzim
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I need to replace 1,800 mini lights. The existing set is wired 100 bulbs per set (circuit). When I replace an existing bulb in the old set with a bulb from the new set and test, the new bulb instantly burns out like a flash bulb on a camera. The new bulb also comes from a set wired 100 bulbs per set.

What do I need to know to get the correct bulbs?

Discarding the existing set of lights and replacing them with new sets is not an option.

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Try and find replacements the same brand as the ones you are replacing. I had the opposite issue, my replacement bulbs would hardly light up. They were so dim you couldn't tell if they were working or not. I guess you could check the voltage of the socket and compare it with other strings of lights to get you in the ballpark.

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I've had the same problem before. Dosn't make any sence, because if they number of bulbs per circut are the same on each string, the bulbs *should* be the same voltage and work the same. But I too have robbed from a 100 light string (which is 2 circuts of 50 by the way) only to plug them into another that's in use and find either the half dim problem, or they are super nova. No answers...

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vroach hit it on the head I do believe. There are two different volts for minis. I am sure someone else on here knows what they are. You are probably using a bulb that is the wrong voltage for that sting. Give it a little while and I know someone will chime in with how to determine what voltage that string is. Wish I could be of more help but I honestly never go through the hassle or replacing a burned out mini bulb. I just go ahead and replace the string if I get more then two bad bulbs.

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vroach hit it on the head I do believe. There are two different volts for minis. I am sure someone else on here knows what they are. You are probably using a bulb that is the wrong voltage for that sting. Give it a little while and I know someone will chime in with how to determine what voltage that string is. Wish I could be of more help but I honestly never go through the hassle or replacing a burned out mini bulb. I just go ahead and replace the string if I get more then two bad bulbs.

There are more than two different voltages - 2.5V, 3.5V and 12V are all pretty common, but you can determine the voltage by the number of lights per string:

50 (or a multiple of 50): 2.5V bulb

35 (or a multiple): 3.5V bulb

10 (or a multiple): 12V bulb

Within 2.5V bulbs there are two common current ratings as well, known as "SB" (super bright) and "ES" (Energey Saving). If you put a 2.5ES bulb into a string of 2.5SB bulbs, the new ES bulb will go out like a flashbulb. If you put an SB in an ES string, it will barely light up. Putting a 2.5V bulb into a 3.5V string will cause instant flash-bulb as well. You can determine if a 2.5V string is "ES" or "SB" by measuring the wattage (e.g. using a Kill-O-Watt meter). A 100 light SB string uses about 40W, while a 100 light ES string uses about 27W.

As Chuck mentioned, if the string has many bulbs out (but shunts intact), replacing a single bulb will cause instant failure - you need to replace all of the bulbs in one go if you have a string that's had a "cascade failure" where all bulbs have failed over to the shunts.

HTH

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What stinks is that I've not found a way to ID the difference between a ES bulb and a SB one. When not lit, they appear the same.

CarlD I'm sure that's what's going on here, I remember now this same conversation on PC last year, lol.

The only way to ID them is to know what kind of set they came out of, and then label them as such.

Or do it the Mike Method: Get out a string of SBs and a string of ESs to pull bulbs from. Use one as a replacement. Flash Bulb or Dim? Use the other :D.

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Ok, so what is the difference between ES and SB should be fairly easy.

lets think this through and see if anyone can find fault with this. Lets say that both bulbs are from a 100ct string. But the string is really 2 50s. So as someone mentioned earlier that would be a 2.5 volt bulb. So the only really difference is the watt of each string. With a lower wattage going to the ES and the SB would be a higher wattage string. Now using Watt's law if the voltage is the same but the wattage has changed, then the current draw must change right? So now using Ohm's law and again the voltage is the same, but the current has changed, then the resistance must also change.

Thus gents with a simple ohm meter one can determine if one has a EB or SB bulb in their hand. Thats provided it is not blown. The EB bulb will have a higher resistance than a SB.. From what you all are saying. The op is trying to place a EB bulb in a SB string. If you take an old SB string and populate it with one single EB bulb it will make like a flash bulb. But if you exchange all of the bulbs at one time, then your old SB string will become an EB string. What happens when you place a EB bulb one at a time is that it's higher resistance than the rest of the bulbs will drop more voltage across it than the others and instead of 2.5 volts across it as it should be. You are dropping (just pulling number from thin air to illustrate) say about 10 volts, POP!

Also learn about Kirchoff's law...The total voltage drops, shall equal the total voltage applied.

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Wow, It's great having people in this forum that can explain all this stuff. I've been stuck on this same issue myself when i purchased 4 1000ct trees from sears at 85% off last year. Got home and noticed that one was multi (which i didn't want) Called around to the others stores and everyone was out of them, and go figure they don't offer the same tree this year. Now time to figure out what spare strings i have and start replacing.

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Thus gents with a simple ohm meter one can determine if one has a ES or SB bulb in their hand. Thats provided it is not blown. The ES bulb will have a higher resistance than a SB...

Yes, that should be true - I've often intended to take my ohm meter and attempt to characterize a bunch of bulbs just as you suggest.

One thing to keep in mind though: the cold resistance of a light bulb is quite a lot lower than the hot resistance. This means that the difference in resistance between a cold ES bulb and a cold SB bulb could be only a couple ohms, so a digital meter and good measurement technique could be necessary to accurately distinguish the two.

If anyone goes and does this experment, please post your results!

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I'll be truthful with you CarlD. In MOST applications, the resistance drops as the temperature rises. Are you stating that the filiment resistance rises as it gets hot? I do know that there are a few things this to be true, but did not know that this is true of light bulb filiments. Interesting, learned something new today. I would assume that the SB is a thicker wire for the filiment. So, I would think it's resistance would still be lower than the EB bulb. Also I would assume that both would use the same material (metal) for the filiment. But hey I am no EE designing filiment type light bulbs, so I could be all wrong about this too.

Pitched all of my old strings and have gone totally LED. Otherwise I would jump in with some of my findings also..

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