Monday, 7 September 2009

The noise suppressor board

I forgot to mention the problem I had setting up my new soldering iron stand. I had to use the fluted coil (holder) upside down, because my Maplin soldering iron has a couple of screws by the tip, making it too wide to fit in the normal way up. This necessitated using pliers to force the coil apart at the (now) bottom end in order to twist it out, and to shove it over the plastic support!

Today, I set to, soldering the noise suppressor board, and as before got part way through when I had to pause to ask a question of the forum folk; the screw terminals component had leads but also made contact with two other pads, and I wasn't sure if they were to be soldered as well. The advice came that I could ignore them, so I soldered just the leads.
When it came to soldering on the tiny tiny tabs into huge holes on the board, I was at a bit of a loss. I secured the motor against the back of the board using an elastic band (left by the postie). You can see the capacitors' outer legs left un-trimmed, for soldering to the motor casing later on.

The instructions warn you to use a lot of solder, but it was difficult to heat the large round contact and each tiny motor tab (taking care not to damage it) as they didn't fit snugly together. Eventually I had a mass of solder there, but not exactly shiny, no matter what I did.
Soldering the legs of the two outside capacitors onto the motor casing proved to be even harder. I tried cleaning the casing first, and tried to tin the casing before affixing the leads, but neither joint looks pretty, and in fact I had to re-do the second one three times. Then I affixed the cable tie to hold it together firmly, and this second joint clearly moved!
I ended up using the desoldering braid to remove the solder. That wasn't easy, either - I wasn't expecting the braid to get hot, and I found my hand getting uncomfortably hot holding it. Also, it didn't seem to wick, but I did get a blob off at a time. I wonder if that's because of using the higher temperature, unleaded solder?
I tinned the capacitor lead, and squashing the end of the lead down onto the motor with the soldering iron held parallel and on the topp of the lead (and obscuring the lead from view) and moving the iron along and off the tip of the lead as soon as the solder melted.
This fourth time made contact.

Not exactly tidy, though!
Still, I set the multimeter to the lowest resistance setting and used it to check from the left screw terminal to the left tab on the motor, and from the right terminal to the right tab on the motor, and both gave 0.05 ohm, so I believe I have continuity despite the problems encountered.

I guess next it will be my first try at reflow soldering....

1 comment:

  1. It is difficult to solder large, heavy components with a small soldering iron - you have to transfer a lot of heat to the components.

    When I borrowed a soldering iron from my father-in-law, he lent me two - one small for electronics, and one for soldering battery connectors - it was hotter than a blast furnace, and about the size of the largest screwdriver I've seen (1cm wide)