A question on PCB/solder condition

[guitar_199]

I am about to be doing a recap on my ultimate project radio ... the SBE Console V.

I am attaching a photo of the PC board... solder side.

Notice how it is all kind of dulled.... light grey?

This is probably dumb to ask....but would it pay off any to reflow every bit of that? Just reheat it and let it flow? OR.... does "if it ain't broke, don't fix it" apply better?

 

[guitar_199]

Oops..... forgot the photo......

 

[2NC995]

I’d be tempted to clean it up and leave it, maybe some others will advise differently.

 

[TM86]

Unless you suspect a cold solder joint reflowing is probably not a great idea.

These are early double sided boards, which are kind of finicky about the soldering around the points that connect between the top and bottom sides. Mess that up on a massive reflow job and good luck ever finding it.

Clean it the best you can without hosing it down in the backyard and call it good.

 

[guitar_199]

Yeah, I was wondering about those "through connections". I watched several of Mike's videos on the SBE Console V and he goes over them pretty thoroughly. I have a copy of the service manual and one of the drawings shows the locations of each and every one of those in fair detail. Still.....that said.... I'd just as soon not have to chase it down....

 

[Tallman]

I personally would not advise you to do it. You just might cause a fatal flaw in the equipment.

 

[autotuner]

I'd leave well enough alone. Recap away,but ignore the rest.
As a side note, we used to have a store called PrePak electronics. The had all sorts of surplus and bulk buy stuff. I spied a built 70 cm kit radio really cheap one day. Beautifully finished, except the guy had used epoxy instead of solder.

 

[nomadradio]

The gray satin surface finish of the factory solder has to do with the machine-soldering process used to build it. The parts are inserted and the solder side is coated in flux. The board is passed over a "waterfall" of molten solder. Called "wave soldering", the icicles that will hang from the copper foils are blown off with a hot-air knife.

The flux is washed off, exposing the solder to the oxygen in the atmosphere. This causes the darker, satin finish you see.

It's easy to spot any hand-soldered connections, they'll still be shiny. The layer of flux left after hand soldering keeps the solder shiny so long as it's not removed.

The double-sided technology they used often has problems with connections from the top to the bottom-side foil. Gently flexing the board usually reveals any of these.

And if it ain't broke, don't do like the shade-tree mechanic and "fix it 'til it breaks."

73

 

[guitar_199]

Tell me you are kidding????
Epoxy .......where solder should be??????

Beautifully finished, except the guy had used epoxy instead of solder.

 

[TM86]

Tell me you are kidding????
Epoxy .......where solder should be??????

Maybe he ran out of Gorilla Glue?

 

[nomadradio]

Decades ago, there was a so-called "conductive" epoxy that was promoted as an alternative to solder. Contained metal particles to make it conduct.

I remember reading a couple of magazine-review articles. One written by a guy who built a transceiver, or maybe a receiver kit with it.

He said things worked okay.

I remember another review that was not so positive, but the details are gone with the sands of time.

If it was all that, we would all be using "lead-free" epoxy instead of solder all these years later.

73

 

[Tallman]

Tell me you are kidding????
Epoxy .......where solder should be??????

Some of the machines that did the pick and place for surface mount would put down a tiny dab of glue to hold the parts in place until they did the solder oven reflow.
The solder paste had flux in it that might look like epoxy if it is old enough.
Try touching one area with a soldering iron and see if it melts.

 

[autotuner]

Nope. Full coating of epoxy. Looks like bent all the leads over and poured in the stuff. Not one solder joint to be seen. Epoxy on the back of pots, everywhere.

 

[Tallman]

Does it look like Conformal Coat? Some one in production did not notice the lack of solder and did the conformal coating.
Conformal coating is used to protect the circuit from moisture.