Botched a repair job, can it be salvaged?- Mtbr.com
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  1. #1
    viva la v-brakes!
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    Botched a repair job, can it be salvaged?

    I have a Exposure Max-D that, to make a long story short, has been in the repair bin for a while. Last night I took it out and realized that the problem was simply that the skinny black wire next to the skinny grey wire was not connected to the circuit board.

    Easy fix, right?

    [grabs soldering iron]

    Hold my beer!

    10 minutes later... I got it soldered in place, with some difficulty, but I must have done some other damage. Now it turns on, but the light emitted from the main LEDs is extremely dim.

    I got some solder on that chip labeled R100. Maybe I got it too hot, or the solder is shorting it out, or I created a short elsewhere?

    Any help?





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  2. #2
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    Sure looks like you've made a solder bridge to the resistor R100.

    The black and gray wire look to be in pretty rough shape so if it was me, I'd be redoing both of them.

    Thing is, this really isn't a good device to be learning how to solder to because the battery is connected while you are working on it... it only takes one slip-up where you accidentally short battery power to the wrong component and poof! This may be what happened already, but I would only try to fix this if you can figure out a way to disconnect the battery first.

    Worst comes to worst I would cut one of the leads from the battery at the 1/2 way point temporarily while working on the board and then splice it back together after. Make sure you cover the splice with something durable like shrink wrap so that nothing can short out.

  3. #3
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    Quote Originally Posted by kwarwick View Post
    Sure looks like you've made a solder bridge to the resistor R100.
    So, functionally what does that mean? Does creating a solder bridge cause the resistor not to work correctly?

    Quote Originally Posted by kwarwick View Post
    Thing is, this really isn't a good device to be learning how to solder to because the battery is connected while you are working on it... it only takes one slip-up where you accidentally short battery power to the wrong component and poof!
    This was definitely on my mind while I saw soldering. It was in the off "position", and I don't THINK, and current was flowing when I was doing this, but still kind of breaking the first rule of doing electrical work.

    I'm fairly confident soldering wires on simple electronic devices, but I've never worked on anything this small, or with a circuit board. Can the circuit board and components withstand the heat from your average Radio Shack soldering iron?
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  4. #4
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    Since this light has a "soft switch" power is always going to the main board regardless of if the LEDS are turned on or off so you do need to be extra careful. For soldering surface mount boards like this you might get away with a RS soldering iron if you are really good and have one with a fine tip, but really a temperature controlled soldering iron would be what I would recommend so that you can ensure you don't apply too little or too much heat. Although most components are pretty tolerant of heat, there are limits and the other risk with too much heat or too big a tip is you'll melt the solder for other components and they can actually float out of position of even fall off the board.

    Have I frightened you yet? Yeah, this is really a job for a professional or at least someone with lots of experience soldering on a modern surface mount board like this.

    I've never opened up an Exposure light before, so I am speculating a bit about the interior layout but the black and gray wire look to be coming from the switch on he back so if one wire had been disconnected then the signal to turn the LEDs on would never of gotten through.

    I can't tell for sure, but looking at your photo it sees like R100 is precariously close to the RED (+) battery terminal. Hard to know for sure without examining the board up close and metering out where the traces are going, but if that side of R100 is connected to the + battery terminal then that solder bridge has essentially created a short that is putting battery voltage into the black wire.... pretty much the worst case scenario.

  5. #5
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    I'm pretty sure it doesn't bridge to the + terminal, but I'll take another look, its all so small its hard to see whats going on. I'll post some more photos too.

    Maybe investing in a finer soldering iron would be worth it. If I can get this working, its basically a free light. I just killed a newer one, I presume a similar loose connection is at fault.
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  6. #6
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    Quote Originally Posted by FishMan473 View Post
    I'm pretty sure it doesn't bridge to the + terminal, but I'll take another look, its all so small its hard to see whats going on. I'll post some more photos too.

    Maybe investing in a finer soldering iron would be worth it. If I can get this working, its basically a free light. I just killed a newer one, I presume a similar loose connection is at fault.
    Hey, free is always good.

    Actually I was just looking at your photo and realized that board is in the rear portion of the light and those two wires are going towards the LEDs in the front, is that correct?

    If so this could certainly explain the LEDs coming on very dim as you've created a short between the black wire (one of the wires for the LEDs) and the R100 resistor. This may have damaged the driver or if you are very lucky it will be OK once you remove that solder bridge.

  7. #7
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    Taking the light apart, the grey wire came loose too. So I took the black wire off again and broke off as much solder as I could with some forceps. There seems to be some residue on the circuit board though. How can I remove this

    Photos attached

    I guess I'll start by unwrapping the battery cells and see if there is a easy way to disconnect those wires.

    Then should I get a finer tipped soldering iron? Or is there another way to connect these small cables? It looks like originally they were inserted though the circuit board. Maybe soldered on the other side. I'm not sure how to get access to the other side of the board.




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  8. #8
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    Im already disturbed by looking at the internal design of such an outrageously expensive light.... Battery pack just hangs out in the housing beating up against the wires on the driver....

    That said from what I am seeing:

    first dont open the pack, its pointless. You have to desolder at least one pack wire form the driver so there is no power from the battery coming in.

    The wires you soldered are headed to the LED in the front of the housing? and there is already a bridge in the circuit built in between r100 (which is the current sense resistor) and the negative wire for the LEDs which is normal design. HOWEVER without a picture with the solder cleaned off from there I cant tell you for sure. The bridge you created is hiding the rest of the circuit layout.

    If the LED is dim one of the few things could have happened, most of which means the light is toast no matter what:

    Driver got shorted by the broken wire hanging around

    Attempting to fix you shorted out the driver as they should NEVER be touched with the battery still connected.

    LED is toast because it got shorted/over voltage from the wire hanging around in there.

    NOW if somehow you damn lucky and that solder bridge isnt supposed to be there and no of the above are true, then you might have a chance at fixing it. But you need some better know how (or a buddy to help that does know how) to remove the pack without shorting anything out or damaging the pack, then clean up that solder bridge and finally reinstall wires correctly. They are thru hole and you dont NEED access to the other side if you have a decent soldering iron (not cheap radio shack crap, a real one) and know how to set everything up so you can push the wire through the molten solder without over heating the driver (its going to be pretty tolerant to heat but a novice with a crappy iron can cook it).

  9. #9
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    Breaking off solder isn't the way to do it as you can damage components or rip traces off the board. Check out: How to Remove Solder: 5 Steps (with Pictures) - wikiHow

    I wouldn't bother up-wrapping the battery pack as it is all soldered inside too and then you'll have to deal with re-wrapping it.

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