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~DOC~

This may be a rookie question but it’s happened twice now

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Part of a string is dimming. Top half. Every bulb is just barely lit. I did it the hard way pulled every light affected and used in another good set. All lights worked fine. I ended up pulling the string off and put another one back on. Now I have another. Any suggestions or is this string just bad.  

 

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Bad bulb maybe?  Adding too much resistance to the line after that bulb?  

I'm no expert, but I'd replace the first dim bulb and/or inspect the strand between it and the last good bulb. 

 

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What kind of strings?

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We are talking about a single strand and not 2 strands end to end?

Is there a bulge just before the dim section: Bad rectifier (chubby bulge) or wrong resistor (slim buldge).

Or is one light OUT. (bad bulb in a just keeps burning string). Or you have a 'flasher bulb in that section

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resistor at the end a string of LEDs. You can find it inside a little weatherproof cap along the string. A 50 cent fix at an electronics store. In my case it was a 1.8K Ohm 5% 2W resistor. Just replace with the leads bent upwards inside the holder.

 

check make sure the bulb holders are not rusted. Which could  Cause a resistance .

 

Check the wire for any cuts. Might have a small short from the wires having a small cut and shorting out. 

Edited by Richard365

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1 hour ago, k6ccc said:

What kind of strings?

Holiday time lights from Walmart never had this issue with these lights. Usually it’s just lights out.

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1 hour ago, Richard365 said:

resistor at the end a string of LEDs. You can find it inside a little weatherproof cap along the string. A 50 cent fix at an electronics store. In my case it was a 1.8K Ohm 5% 2W resistor. Just replace with the leads bent upwards inside the holder.

 

check make sure the bulb holders are not rusted. Which could  Cause a resistance .

 

Check the wire for any cuts. Might have a small short from the wires having a small cut and shorting out. 

Funny since last night this string is now working. I already removed it but. Hard to find problem when it stops doing what it was. 

 

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I bet there is a bad bulb or two in the dim section, but it may also be a bad rectifier or resistor in the string. I have run across this issue mainly with blue led's. The LED Light Keeper bulb tester is very helpful to find the bad bulbs, but it can be a tedious process...

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DOC, back when I used to fix TVs in the late 70's and 80's.  We used to have the same problem, trying to fix a TV that acts up for a few seconds or once a week, made your hair turn grey. 

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Ok sorry It was easier to replace the string. Now that I am packing I am working to fix the light string. The current one I am working on the lights are out at the end. Checked all the bulbs and they work. Pulled my multimeter out. Checked voltage to the end of the string of the female plug. I have 120v. Now I suspect the resistor. Went to the resistor. I get 110 volts at the in side. And nothing on the out.  The bulb before this showed very dim when I checked this way. I am as I keep telling work not a expert at small electrical. I am taking the resistor is bad. Are my thoughts correct? 

If I am correct now I need to get a resistor. Where is a good table I can use to find the right resistor and where is the best place to buy. I have a lot of these string so might as well buy a few extras. 

I always repair all string prior to packing away. When I have come across these situation I scrapped the string. I want to repair them. Any help. 

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1 hour ago, ~DOC~ said:

Ok sorry It was easier to replace the string. Now that I am packing I am working to fix the light string. The current one I am working on the lights are out at the end. Checked all the bulbs and they work. Pulled my multimeter out. Checked voltage to the end of the string of the female plug. I have 120v. Now I suspect the resistor. Went to the resistor. I get 110 volts at the in side. And nothing on the out.  The bulb before this showed very dim when I checked this way. I am as I keep telling work not a expert at small electrical. I am taking the resistor is bad. Are my thoughts correct? 

If I am correct now I need to get a resistor. Where is a good table I can use to find the right resistor and where is the best place to buy. I have a lot of these string so might as well buy a few extras. 

I always repair all string prior to packing away. When I have come across these situation I scrapped the string. I want to repair them. Any help. 

Bad resistors usual are pungent. Besides, you need to know the form factor of the resistor.

Gone are the days of popping down to Radio Shack for simple parts like resistors and fuses.

We have a Local Fry's. Their stock is pathetic for the last few years. Giant holes in the values, No 1/4W  at 2 stores (I was making terminations for the RS485)

 

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So I sacrificed one string Cut the known good resistor and spliced it in. All is better.  But I don’t want to do this for every string. I guess I will take it into work and ask one of our young brilliant electrical engineers (cough) to help me out. 

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