Soldering Question

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by saltysnail, Feb 16, 2009.


  1. saltysnail

    saltysnail Member

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    Feb 11, 2009
    I'm in a bit of a predicament and I need some help. I was trying to unscrew the pcb in my amp from the chasis, but the screws were in so tight that one ended up getting stripped, and is still firmly in place.:bkw
    As a result, I don't want to try to force it out, because it could (and with my luck would) wreck the board. So essentially, I'm forced to only work with the top of the board.
    My idea is this:
    I want to change a resistor value on my amp from 220k to 100k, and I'm wondering if it's possible to clip the leads of the current resistor super close to the resisitor itself, and to solder the new one onto those wires.
    My questions:
    Will this work?
    Will it sound alright, or will the sound be degraded?
    If I do a bad solder job, what will happen to the amp and what will happen to the sound?
    What will happen if the connection is cut compeltely?

    The resistor is R7 in the following schematic:
    http://www.blueguitar.org/new/schem/misc_amp/crate_v16_palomino.pdf
    It is off of pin 6 on v1b

    Side question: what is the part optc39 that says DO NOT INSTALL? I noticed that it was an empty space on the pcb as well.
     
  2. saltysnail

    saltysnail Member

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    :BEERExactly the answer I was looking for. Thanks a ton.
     
  3. 5992

    5992 Member

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    You can also solder a 220k resistor in parallel with the existing one to give you 110k. This will tell you if you like the mod or not before clipping out the old 220k.
     
  4. FrankieSixxxgun

    FrankieSixxxgun Member

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    Yeah, and if you like it, just leave the parallel resistor in. That way if you wanna sell the amp later in stock form you actually can. Reversible mods are the best mods.
     
  5. andrekp

    andrekp Member

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    The thing to watch out for is that you heating for the new soldering doesn't melt the old solder and not re-harden properly (cold solder joint).

    I'd also carefully investigate the stripped screw. IF it's loose enough, or can become loose enough, to fall out on its own when your amp is all closed up, it could be a shorting hazard. Any any amp has voltages that would not make you happy if you found them on the chassis... It's worth a check, or maybe a trip to a tech if you don't feel confident about your skills in removing it properly.
     
  6. donnyjaguar

    donnyjaguar Member

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    Just dremel a groove across the screw and remove it with a slot screwdriver. Use a really skinny (cheap) cut-off wheel for best results. I've never busted a screw doing this, but if you do, just grind the head off and drill out the screw once you get the PCB away.
     
  7. saltysnail

    saltysnail Member

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    Funny you should mention the parallel wiring. I got a pack of 5 100k resistors, and decided right after I asked this question that, rather than clip the 220 and deal with all of that, I'm going to wire 2 100k's in series, and put those in parallel with the 220k. A simple, removable solution. It'll end up being about 105k, which is close enough for me.
     

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