Stuck on a noisy amplifier fix, I traced it to a cold joint. Some say reflow everything, others target the suspect. What's your take?

I had this old amp with constant hum. After checking the usual grounds, I found a single cold solder joint on the power supply. My buddy says to reflow the whole board to be safe, but I think just fixing the bad spot is enough. How do you guys handle this?

3 comments

3 Comments

amy_nelson1mo ago

Target the suspect joint every time, why create extra work? Fixed a cold joint on my old receiver five years ago and it's been silent since. Who wants to risk heating up good parts for no reason?

nathan_johnson541mo ago

But how do you know for sure which joint is the cold one? Symptoms can point to one area, but the real issue might be elsewhere. On my old amp, the left channel kept cutting out. I reflowed the obvious joint, but the crack was actually in a trace near the input jack. So, do you test the circuit first or just go by what seems likely? Missing the root cause could mean the problem comes back later.

henderson.mason29d ago

I read a tech blog where a guy fixed a vintage radio. He said to always check the whole signal path with a meter before touching the iron. He found a bad resistor that mimicked a cold joint at the volume pot. If he had just reflowed that, the real fault would have cooked the new solder in a week. Testing first saves time.