Soldering Advice

[RickTock]

Hello,

I'm working on a Seiko 3823 movement from the early '70s. There's a condenser that protects the battery circuit, and the solder that held the condenser to one of its mounting tabs has let go. This is smaller than anything I've soldered before, and I would be most grateful if folks could point me in the right direction in terms of tools and technique needed.

I have a Weller 5-40watt soldering station and some rosin core solder. Don't want to make things worse...

[Bearman]

Hello Ricktok, I've done a fair bit of soldering in my past. I'd say you've got a good iron there but I'd suspect the tip is going to be way too big. You'll need a fine tip, either buy one of the right size or file one down to suit.

Being that it's from the 70's there's a good chance the solder contained lead, unlike today. Mixing old and new solder can be problematic, using flux and keeping it clean and grease free helps.

Depending on your soldering skills you may be able to dab it back on using the solder already there, but you won't know until you try. Careful with the heat.

An alternative way would be to use sliver conductive paint, but I don't think it'll help in your case, holding the component to the tag.

I'd also practice on some scrap wire, components too especially at that scale, it may help in dialing in the temp and melting point of your solder, and how it flows. 

Good luck, let us know how you get on.

 

 

[HectorLooi]

Are you sure it's soldered? I've worked on Accutrons that were spot welded and no amount of heat will be able to release that.

But if it's soldered, flood the area with flux first. It helps to transfer heat to the joint and prevents oxidation. I prefer solders with lead. Lead free solder is a real pain to use. Put a dab of fresh solder on the joint, it will help to melt the old solder.

[RickTock]

7 hours ago, HectorLooi said:

Are you sure it's soldered?

I *think* so. Here's a zoomed image with arrow pointing to the joint in question.

An

 

Any recommendations on how to hold everything steady and aligned while I solder? The alignment of the little tab that broke off is pretty important (see diagram below). I was thinking of setting the condenser and its affixed mounting tab in a bit of Rodico, holding the detached tab in tweezers with one hand and soldering iron in the other. Not sure if I'm steady enough for that though.

[HectorLooi]

I would mount it back on the movement and solder. But make sure you prime the tab and capacitor lead with fresh solder first, to minimize contact time with the hot iron. 

[watchweasol]

Hi a pair of crossover tweezers would do the trick as they have to be pressesd to open, naturally in the closed position or an anglers heamostat used for removing hooks as these have a lock on the handle.  To solder fine components like coil wires etc, get some copper wire and wrap round the soldering iron bit and file to shape and tin. The iron will transfer the heat to the copper wire. Also how about solder paste which contains both solder and flux.

[CYCLOPS]

look for paste solder.....in a syringe

[RickTock]

To wrap up this topic, I never did solder the part. I purchased a NOS replacement on eBay and used that, with soldering the old part as a back-up plan. Interesting enough the replacement did not look soldered, but rather spot welded as @HectorLooi mentioned.

I appreciate all of the kind and helpful advice. I will help me when I one day tackle soldering something so tiny.

Cheers!