L0-Ti Mod Help, Please

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Frank_Zuccarini

Newly Enlightened
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May 16, 2006
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With continuing help from the CPF, I am attempting to replace my L0-Ti's Luxeon LED with a Seoul P4.

I have successfully opened up the L0, exposing the LED. I would now like to desolder and remove the Luxeon, but I am a bit confused and nervous.

I appologize the my camera's quality, but in the photo below you can see the black wire lead coming out of the circuit board/heat sink at about 11:00. It appears to be connected by a strip of solder which runs clockwise around the face to about 2:00, where it is connected to the Cathode terminal, just above the notched lead frame.

Question 1: Do I simply desolder and wick up this connection?

At 9:00 in the photo, the Anode terminal appears to be soldered directly to the brass-coloured heat sink (?) which appears to ring the entire LED.

Question 2a and 2b: Is my observation above correct, and if so, is this something else I desolder and wick up?

At 6:00 in the photo is the red wire, which seems to be soldered directly to the same brass coloured heat sink described above.

Question 3a and 3b: Is this observation correct, and if so, are the two hemispheres of the heat sink electrical oposites since the black wire which runs from 11:00 to 2:00 has solder that touches the same heat sink along it's entire route?

Can anyone explain to me what I am really seeing, and what I need to do to remove the LED so that I can then ask a bunch of questions about how to solder in the Seoul P4?

Thank-you for any and all help..............Frank

L0-Ti-01.jpg
 
Frank, in your picture, at 3:00 and 9:00 are the leads from the emitter. They are attached to the circuit board "traces" which also have the red/black wires attached. Remove the solder from the emitter leads and lift them up slightly away from the board. The emitter may be attached to the board with some type of adhesive requring you to carefully pry it off. Looking at the picture, it looks like the negative (black) side of the trace may go under the slug of the emitter. If it does, you will have to be careful as the P4 slug is common to the positive lead. When you mount the P4, be sure to check that the positive side is isolated from the negative before you turn it on.
Good luck, Bob
 
Thank-you, ledaholic (Bob) for your description and help. I appreciate it.

Unfortunately, I am still a bit confused.

>>Frank, in your picture, at 3:00 and 9:00 are the leads from the emitter. They are attached to the circuit board "traces" which also have the red/black wires attached. Remove the solder from the emitter leads and lift them up slightly away from the board. The emitter may be attached to the board with some type of adhesive requring you to carefully pry it off. Looking at the picture, it looks like the negative (black) side of the trace may go under the slug of the emitter. If it does, you will have to be careful as the P4 slug is common to the positive lead. When you mount the P4, be sure to check that the positive side is isolated from the negative before you turn it on.<<

The black wire does appear to be attached to the negative (SSC says 'cathode', is that the same thing) lead from the emitter, but it runs along from 12:00 to 3:00 touching what I think you refer to as the 'slug'. Is that by intent? Why doesn't that cause a short?

The other lead (positive/anode) is soldered directly to the 'slug', and not to the red wire. What's up with that, and why is it not a problem with the 12:00 to 3:00 bead of solder on the same 'slug', which is from the other lead?

I'm the first to admit that I'm thick about this stuff, but I'd like to proceed if you can explain things to me in a more elementry manner that I can grasp.

Again, thanks...................Frank
 
Frank, a white Luxeon emitter, without going into a lot of detail, uses an isolated slug. The "slug" being the metal portion opposite the light emitting end or the bottom of the emitter. The SSC P4's slug is common with the positive terminal which can cause problems if the surface the emitter is being attached to is at a negative or ground potential. I can't really tell by your picture, but the trace from the negative side may be attached to the area of the circuit board or heatsink where the P4 will be attached. You will either have to isolate the mounting surface from ground or isolate the slug from the mounting surface using a non conductive adhesive. Whichever way you do it, just double check before you power it up. In your picture, the emitter is mounted on to what looks like a circuit board. There are two areas of gold looking hemispherical shaped traces. The traces are what are used to conduct current to the device being powered and are a convenient way to solder components and make wire connections. There was really no reason to run the solder from the wire to the emitter lead the way whoever built yours did. When you get the Luxeon off the board and clean up some of that solder, it should become clear what is going on.

Bob
 
Thank-you, Bob. I believe that I understand it now.

I thought that I was looking at the 'slug', when in fact I was looking at the two areas of gold/brass hemispherical shaped traces. And these two traces are electrically isolated from one another, and can be used in liew of the actual 'tabs' that protrude from the emitter for current conduction. That explains the presence of solder in more places that I thought necessary.

And I'm aware (from other postings) that I must isolate the Seoul LED from the slug. I've purchased a small quantity of electrically neutral arctic alumina thermal epoxy for just that purpose.

I think that I can proceed from here.

Thank-you, thank-you, thank-you........................Frank
 
I screwed it up, Bob. Likely due to my woefully inadequate soldering skills, and complete lack of electronics education.

It's not as easy as you guys make it sound. I do appreciate the help, though.

Thanks again..................Frank
 
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