Question about using a heat gun vs a soldering iron for stubborn joints on old boards

I was working on a 1990s stereo amp last week and hit a spot where the solder just would not melt no matter what I did with my iron at 400C. After 20 minutes of frustration I grabbed my heat gun on a low setting and hit the joint from the back of the board, and it flowed right out. But I'm worried I might have damaged nearby caps or the board itself. Does anyone else use a heat gun for tough desoldering jobs, or is that a shortcut that will come back to bite me?

2 comments

2 Comments

abbycraig18d ago

My old boss used to do this on purpose with this 1970s Marantz receiver he was restoring, and he said the trick was to keep the heat gun on the lowest setting and never hold it still for more than 5 seconds. The real danger isn't the caps so much, it's that you can cook the board itself and make it brittle over time, especially on that old paper-based stuff from the 90s. I've done it a few times on ground planes that just suck the heat away, and I always use a small nozzle and some kapton tape to cover anything plastic nearby. Just don't go blasting it like a hair dryer on full power and you should be fine for those one-off tough joints lol.

abbycraig17d ago

Oh man, I gotta disagree hard here. That low heat trick might work for one joint but you're way more likely to cold solder the whole area and end up with brittle joints that crack later. I've seen too many guys try the "gentle heat gun" method and end up with boards that look fine but fail after a few months because the solder never really flowed right into the ground plane. Kapton tape's great and all but if you're not getting the board hot enough to actually melt the solder properly into that thick copper, you're just wasting your time and risking a return job down the line.