Christmas mini light voltage

[Jimbert]

I have an artificial tree with about 500 mini lights. They are arranged in several strings and appear to be wired in parallel. I'm trying to determine the correct voltage for replacement bulbs. There are several burnt out and/or missing bulbs. The rest of the bulbs remain lit. With a multi meter I measure 120 Volts at the socket of the missing bulbs. I've never seen 120V mini lights. What am I missing?
Any help appreciated.
Thanks,
Jim B

 

[davenn]

Hey Jim
Welcome to EP

are these lamps supplied from a plugpack ?
if so what info is on the plugpack label ?

maybe some photos

 

[KJ6EAD]

Typically the bulbs are 6V each, wired in series strings of 20 bulbs that are then paralleled into a common plug, however, there are some lower voltage exceptions.

It's almost never worth the time and trouble to repair those but if you do, use one string as a supply of spare bulbs instead of trying to find them sold as replacements.

A prewired tree is one of the exceptions to the above.

You're measuring 120V because with the circuit open (the high impedance of your meter is like an open circuit) the bulbs in series don't light and appear as low resistances passing almost all of the supply voltage to your meter. Set your meter to measure AC current and try again. You should be able to calculate the voltage drop of the missing bulb from that. Expect about 10-70 mA.

 

[davenn]

It's almost never worth the time and trouble to repair those

totally agree ... I have just tossed ALL my coloured lamp ones and replaced them with LED strings instead, cheaper, much more reliable, less power used etc etc

 

[chopnhack]

Good for you Jim! The bulbs I have seen on E-bay are mostly 2.5v and some 3.5v - look up: replacement christmas light bulbs as the search phrase.

 

[Jimbert]

Thanks everyone for your reply. The lights are installed in a prewired tree and difficult to remove. After closer inspection I discovered that what appeared to be a single bulb out was really an entire string and indeed was wired in series. The lights and limbs are so dense it was difficult to see that the other lights on the string were out also. I've yet to discover whether the bulbs are 2.5 or 3.5 volts but I'm sure it's one or the other. Your sage advice has caused me to look deeper into the problem and find the solution.
Thanks again,
Jim B