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CIRCUIT BOARD TYPE POT? (ie. EMG BTC,etc)

Discussion in 'Pickups & Electronics [BG]' started by luknfur, Mar 31, 2004.


  1. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    Think the problem is resolved but been intending to post and still curious about removing one of these boards from a pot. Never put one together so not sure how they come apart. They solder on at the pot terminals which creates a problem since it's all 3 terminals. Do you just get a soldergun tip long enough to lay across all 3 terminals or what?
     
  2. you'd probably want to buy a solder sucker... its basically a hand operated sucking device that removes solder from joints like that, thats probably your best bet! :)
     
  3. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    No, purchase a solder sucker (no, it's not an April Fools joke). It is basically a vacuum pump. You heat up the solder with a soldering iron, then use the pump to suck up the solder. Sounds stupid but it works.

    You can also buy unsoldering tape. You lay the tape on the solder, heat up the tape and the tape absorbs the solder. But I like the solder sucker better.

    Or, for a few 100 $$$ you can buy a desoldering station with the vacuum built in!
     
  4. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    Yeh, solder sucker was my first thought but don't have one and don't know how well it'd work but I've heard plenty about them so I know they're being used which is a pretty good indicator they're useful. The tape I'd forgot about and seems I heard it refered to by another name that escapes me.

    I've got an old TCT preamp with a mid pot like I've never seen - circuit board with all kinds of crap wired to it and there's a couple wires running in between the stuff that I can't get to becuase of it. Great premap but I'm transforming it to an outboard and got static when I fired it up afterward. While it was in the bass it was all crammed together in the cavity - pathetic. Couple wires seemed loose on that board after removal but I ran a 25K volume on it as an outboard without thinking twice. I noticed today the original was a 250K and I'm assuming that's the source of the static and hoping even more cause I really don't want to mess with that board. But I figured this is something I may need to know in the future regardless.

    Appreciate the info.
     
  5. I've used solder suckers for years. They are great, and inexpensive. Rad Shack may have them I don't know. The other stuff is desoldering braid, I know the Shack has that stuff. It doesn't work as well, IMO, especially if you have large solder joints to unglue. You could mail order a sucker from Digikey, (www.digikey.com) if you can't find it anywhere else. something else I do is to heat the joint and then tap the board on the table top so the molten solder comes out. Probably not the best for the circuit board though.

    You might haveluck with the method you started with - layin g the soldering iron across all three terminals. But I know the BTC has a concentric pot, which has 6 terminal.

    The whole idea is a good one though, I thought about doing just that with a BTC I had once, only in reverse. Ended up trading for for the style I wanted though.

    BT
     
  6. Passinwind

    Passinwind I Know Nothing Supporting Member

    Nope, that'll tweak the board when you rock the pot. If you know you're going to replace the pot, cut the leads just shy of the circuit board. Use good flush cutters, not dikes. Then you can remove them carefully one at a time, using needlenose pliers or a hemostat. If it's a double sided board, this is going to be by far the easiest method. Even though I have a desoldering station, I still cut the leads first in most cases. Pots are generally a lot cheaper than circuit cards.

    I strongly prefer solder wick to bulb suckers or the piston style ones for most circuit board repairs. They all have their place though, and solder wick takes some time to get good with. One big advantage to it it that it reduces solder splashes, which sometimes create big headaches. You have to tin and trim solder wick frequently, so practice on junk stuff quite a bit before you try to use it on anything important. Solder wick comes in a lot of different sizes and formulations too. The Radio Shack stuff is actually pretty decent IME.
     
  7. Especially for small work, desoldering braid (solder wick) is the way to go IMHO. Much better than solder sucker bulbs because it will quickly and easily remove ALL the solder. Here's the trick: Start with a fresh area of solder wick, at least a half inch or so away from the last used part. Lay the solder wick on the joint to be de-soldered. Then put your soldering iron on the soldering wick--NOT on the solder joint. The solder wick must be hotter than the joint. The wick will heat up, then it will heat up the solder joint, then the solder will go up the wick like magic. When you're done, pull a little more wick out of the spool, and go to an unused part of the wick, and start over...

    This is the ONLY technique that can safely desolder multiple connections like an IC chip. You'll never get an IC chip free with a solder bulb, it won't get all of the solder.
     
  8. luknfur

    luknfur

    Jan 14, 2004
    DIXIE
    Appreciate the feedback.

    The 25K pot unfortunately wasn't the problem. But, yeh, solder wick is what I was trying to think of. The pot itself is fine and the rest of the harness looks fine. Hum increases anytime I get my hand around this pot and I get a crackle when I touch a couple of the wires that I'm assuming are the source and since this pot has more wires growing out of it than the TCT preamp itself, I'm guessing that's the source.

    This board has a capacitor on it, a plastic harness with 5 wires that I can see, maybe 4 or 5 more wires coming and going, a gain control, and in the center is the massive storeage tank looking gismo that's practically as big as the pot. If a pot could look like Madussa, this one would be it. The two wires in question run between the pot top and this tank thing and disappear out of sight. So I figure I either have to remove the board or that tank to even see where these wires go. The tank looks like it has two solder point's to the face of the board and the whole unit looks roughly like a BTC with the face of the board open and accessible. So it may be easier to remove the tank than the board.

    I did have have one of the wires come loose on that plastic harness while it was in the bass. And I got that same hum and crackle out of it. I was able to get a little solder into that harness connection enough to restore it to previous function. And it looks to still be holding.

    So go for the tank or the board?