Yet another Predicta Holiday restoration

[bandersen]

Yes, except that I made these using a different technique. Before I used perf board - this time I tacked them together in free space.

Originally Posted by Down Under

Nice work, Bob.

It's always interesting to see you think up new ways of doing things. Did you rebuild the couplates because they were faulty or because you will be far more confident with the restoration? Surface mount components is a good idea... how do you fit these? Machine, tweezers or just great eyesight and care?

I've worked with small parts for years and my eyes are still god enough so I found this fairly easy.

The couplates that look like a bunch of vertical tubes are really made up of carbon comp and ceramic caps. I've measured a bunch and the resistors are have typically drifted high.

The flat, thin couplates like at the top of my photo are made using material deposited on a ceramic substrate and measure more closely to the specs. So I suggest leaving those alone unless you know for sure they're bad.

As for SMD, I've seen various techniques used. The most basic is to dispense the solder paste with a syringe, place components with tweezers and "bake" the board to melt the solder paste.

More recently, I've seen board vendors supply a laser cut sheet metal mask so you can squeegee all the solder paste on at once. Like silk screening.

[Notimetolooz]

Originally Posted by bandersen

Yes, except that I made these using a different technique. Before I used perf board - this time I tacked them together in free space.



I've worked with small parts for years and my eyes are still god enough so I found this fairly easy.

The couplates that look like a bunch of vertical tubes are really made up of carbon comp and ceramic caps. I've measured a bunch and the resistors are have typically drifted high.

The flat, thin couplates like at the top of my photo are made using material deposited on a ceramic substrate and measure more closely to the specs. So I suggest leaving those alone unless you know for sure they're bad.

As for SMD, I've seen various techniques used. The most basic is to dispense the solder paste with a syringe, place components with tweezers and "bake" the board to melt the solder paste.

More recently, I've seen board vendors supply a laser cut sheet metal mask so you can squeegee all the solder paste on at once. Like silk screening.

Yes, typically when boards are manufactured they use the silk screening technique and solder all the parts at once. You can do it by hand one at a time by placing a small blob of solder on one pad first, then re-melt the solder while placing the part. After that you solder down the other terminal(s).