I have a TN-31 driver that the negative (-) gold pad for soldering the wire to the LED broke off the board, before I attempt a workaround solution I want to run it by the experts first.
Can I solder the negative wire that goes to the LED to the driver’s negative battery pad (located on edge of driver) instead of the driver’s negative pad to the LED? will I be creating direct drive, a short circuit, or loosing the driver’s modes?
So far by looking at the driver electrical traces in the board seems that it should work, what do you think?
I guess the negative wire of the LED goes where the board says LED-, at the round "thing" with the black square in it? If so, I dont think you can solder to the outer ring. But its hard to tell with that resolution..
Its hard to tell from the traces.. you could try to measure continuity between LED- and the ground ring like MRsDNF suggested. You should be able to get contact at the LED- pad.. doesnt seem to be completely gone.
I agree with NightCrawl. It does look like you can still solder to that pad. Only the center is missing. Even if you cut a small piece of copper foil the size of the whole pad and solder it over what’s left of the existing pad to rebuild the pad you should be fine but I don’t think you’d even have to do that.
You can solder a new wire to the “-” pad. My suggestion is to “tin” a new wire, that is; solder the end of the wire before attaching it to the driver. Now, clip the soldered end short and bend it to make a “L” shape. Then you can add a tiny bit of flux to the old pad, press the end of the wire to the pad and quickly touch the soldering iron to the wire end. If you do it correctly you’ll have a nice clean joint and the wire will stay put. Use some alcohol and cotton bud to clean flux from around the joint.
Looks like there are vias through the board in the pad. Look at the other side of the board to see where they come out and double check continuity. If that is lost you may need to enlarge one of the holes to allow the new wire to reconnect both sides of the board. If continuity still exists then pretin the pad covering as much of it as you can and reattach the wire.
I finally were able to fix it, I found that the negative pad to the led is connected to the sense resistors on the other side off the driver, there are small metal gold plated holes that connect both sides.
I had to drill using a very small jeweler drill thru one of those little holes to enlarge it enough for a 20 awg wire to fit thru, I soldered it directly to one end of the sense resistor. polished the contacts and reassembled the driver after cleaning it with deoxit and then progold.
Since I had the light open I decided to replace the thermal grease for arctic silver 5, when I removed the led I noticed that the copper sink has a plastic layer of what appears to be kapton tape, WTF! why on earth would you put tape between the sink and the pad? I peeled it off and then I lapped the copper star to a mirror shine.
Reassembled everything and turned it on, LIGHT! whew! it works! and now I can feel the light getting hot while in use meaning that the thermal compound is doing its job and the tape was blocking the heat from being transfered to the body.
Too late now but some stranded copper cables have individual strands that are the right size to fit in those small holes(vias) after just reaming out the solder mask. That is how I connect the traces on multiple stacked boards.
Thanks for the tip, did consider that but decided against because I wanted the best possible connection that would not break off as the rest of the pad when manipulating the driver, what has me stumped now is why the plastic screen between the copper PCB and the heatsink, not good for heat transfer at all
