Hi, I've got a project that I'm working on and I'm having some trouble with a solder joint. I'm adding an optical output to a Minidisc deck. It's a low-cost deck and the output exists on the pricier models in this line. So the circuitry is there, just no Toslink transmitter. I located a transmitter and proceeded to try to solder it to the PCB. The holes were already there and they were filled with solder. My plan was to just heat the existing solder to insert the part. That wasn't working very well, so I ended up cleaning out a couple of the holes with a sucker and tried to solder the part in with new solder (flux filled "for electronics" solder). The problem is, the new solder doesn't stick to the board, just the post of the transmitter, making a lollipop-shaped stick with the lump of solder at the top. It doesn't make a good connection. I figured I just needed to buy some flux and clean that part of the board with it. The problem is, they have no flux at my local RS (back by the guns in the local hardware store). So I ask you experts, is this the right solution? Is there something else I should do? Where can I order some flux from inexpensively in the USA? Anything special to look for with flux for electronics projects?