Prelit Tree, wires cut

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  #1  
Old 12-15-06, 02:30 PM
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Prelit Tree, wires cut

When my better half started to unpack the artificial pre lit Christmas
tree she evidently cut through a strand of wires while opening one of the
boxes (one row of branches packed per box) with a pair of scissors. Each row of branches on this tree has one string of lights specific to the branch size on that row. Each has a male and female plug end so that one row may be plugged into the next (up to 3 are strung together, and each
run of three plugs into a special extension cord attached to the
trunk (pole) of the tree).

At the point the wires were cut there are 3 wires (all green of course),
while at each plug end there are only 2 wires. I can twist and solder the
cut wires, insulate with shrink tube and electrical tape. But how can I
determine which wire to connect to which (remember they are all green)?

Since the light strings are all tailored to the branches I'd prefer to reconnect
the cut wires rather than get a generic string and try to remove the old
lights and add the generic ones. I would back off however if this presents
a safety issue.

Regards,
Jim

PS: Urgent, only 10 more days to Christmas
 
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  #2  
Old 12-15-06, 02:51 PM
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Please ignore.
 

Last edited by ibpooks; 12-15-06 at 02:53 PM. Reason: Mis-read the original post
  #3  
Old 12-15-06, 03:13 PM
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You are going to have to go by trial and error, unless you can figure it out by looking at the other branches.
 
  #4  
Old 12-15-06, 03:22 PM
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Prelit Christmas Tree, fixing cut wires.

What might I expect as I go through combinations? I'm up to
making the connections and testing each. If all the lights
glow at the same intensity can I assume I've gotten it back
together correctly? None of the plugs seem to be polarized,
so what will happen if I don't get neutral to neutral on a trial?

I'm guessing that the lights have been divided into two
circuits in order to get the correct voltage in each set
of series connected bulbs. That's 2 wires and I would
think the third should be a neutral. But is that how wiring
these end to end strings is really done? I'm getting myself
confused by thinking too much. I'll just start trying the
combinations and see what happens.
 
  #5  
Old 12-15-06, 03:36 PM
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Can you tell anything by looking at the connections of the lights to the wires? Are any of the wires marked in ANY way? Do you have a multimeter? You may be able to tell how to connect the wires by measuring with a multimeter.

You have discovered one of the reasons to avoid pre-lit trees. They look great when they work, but when they get damaged or eventually just wear out, you are stuck with no light. And they ALL eventually wear out. How quickly depends on how well built it was in the first place.
 
  #6  
Old 12-15-06, 04:05 PM
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Prelit Christmas Tree, fixing cut wires.

Yes, I do have a multi-meter. I've been able to identify
1 wire that is connected to one side of the plug. I can do
the same on the other side, identifying 1 wire that is connected
to 1 side of the socket (female plug). I haven't determined much
else for the other 2 wires. On one side of the cut the other 2
wires are connected to each other, either at the plug or at
one of the bulb sockets. On the other sid of the cut I can't
tell much at all. Tracing the wires is near impossible. They
are wound around he wire branches, and covered in many
places with a brown binding. Anything specific I should use
the multi-meter (other than conductivity) to test for?
 
  #7  
Old 12-15-06, 04:10 PM
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Compare the cut wires to the plug connections on another branch..
 
  #8  
Old 12-15-06, 07:27 PM
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Prelit Christmas Tree, fixing cut wires.

I drew myself a diagram of how I thought series lights, with
plug at both ends, would be wired. I couldn't make it fit with
the multi meter readings I had gotten.

(Sorry I'm editing the diagram. it looks ok under edit, but not when viewing after posting)

Male end..............(Hypothetical circuit with cut in middle)..............Female end
(1) (4)
(A) Hot -----------+---------------- ------------------------- Hot (C)
| (2) (5)
+-- bulb -- bulb -- -- bulb -- bulb --- +
(3) (6) |
(B) Neutral ------------------------- -------------------+---Neutral (D)

Continuity as shown with multi meter between
(A) and (1)
(B) and (3)
.
(4) and (C)
(5) and (D)
(6) and (D) (hence (5) and (6))

No connection found from (2) to any point listed on
that side of the cut.

The failure to find continuity between (A) and (2) leaves me to think
that I don't have the correct circuit diagram. I also at this point don't
know if (2) or (5) really lead to bulbs or not. I suppose I could pull
the closest bulb and se if I could get my multi meter probe inside the
minature bulb socket to test if there is a connection or not.
 

Last edited by JTeller; 12-15-06 at 07:40 PM. Reason: Spacing in text doesn't seem to work on actual post
  #9  
Old 12-16-06, 09:03 AM
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Prelit Christmas Tree, fixing cut wires.

Well I'm resigned to the trial an d error method. Though I did determine
that the one wire I found no continuity to either plug does have
continuity to the nearest bulb.

Taking a cue from one of the other posted replies, I unpacked the
next ring of branches and used the multi meter to check the
resistance across the plugs (essentially all the lights). This I figure
gives me a reading that should come close to the ring of branches
I am repairing. I.e., before applying power I can run through the
different possibilities (6 in all) of connecting the wires and check
each at the plug with a multimeter. A dead short is an obvious
wrong configuration, as is an open circuit. Hopefully this takes some
of the excitement out of powering up a given combination.

I'll let you know if I getr it to work.
 
  #10  
Old 12-16-06, 11:49 AM
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Prelit Christmas Tree, fixing cut wires.

Ah, more confusion. The working branch I checked with the
multi meter measured 9K ohms across the male plug. But none
of the combinations of connecting cut ends produced that
result. In fact of the 6 combinations 4 showed shorted,
and 2 showed open circuits. So I've done some more measuring.
Opening yet another box of branches, I found these measured as
shorted across the male plug. Yes, both sets of branches light
correctly when each is plugged in. I guess I was wrong in assuming
that I would see the resistance of the bulbs wired in series on my
multi meter.

I may not be smart, but eventually I'll understand. Maybe after Christmas.

More information (replacing anything I've already posted).
Neither the male or female plugs are polarized
One side of the cut has a male plug. I designate the prongs M1 and M2,
and the cut wire ends as A, B, and C. The other side of the cut has a female socket which I designate F1 and F2, with the cut wire ends as 1,2, and 3.

Continuity checks I have recorded:
M1 to A open
M1 to B open
M1 to C shorted
M2 to A shorted
M2 to B shorted
M2 to C open
B to nearest bulb shorted, other 2 open

F1 to 1 open
F1 to 2 open
F1 to 3 shorted
F2 to 1 shorted
F2 to 2 shorted
F2 to 3 open
1 to nearest bulb shorted
2 to opposite side of nearest bulb shorted
3 to nearest bulb open

Based on this I'm going to try connecting
A to 3
B to 1
C to 2 (I thnk B, C could be flip flopped)

This combination showed no resistance between the male plug prongs
on my multimeter.
 
  #11  
Old 12-16-06, 01:19 PM
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Prelit Christmas Tree, fixing cut wires. completed

The wire connections described previously tested well
(temporary connections using wire nuts). Nothing felt
warm after being on for a while, the lights had about the
same brightness as the next branch.

Twisted and soldered all the connections, slipped
heat shrink tube over each solder joint and heated same,
slipped a larger piece of heat shrink tube over all 3 wires.
Used blank electrical tape to add a little more stability
and hide the tubing (which was bright blue, but all I had
on hand). Retested and everything seems quite alright.
The tree is up.

Thanks for all the ideas and thought provoking questions
along the way.

Merry Christmas / Happy Holidays,
Jim
 
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