Pro tip: check the flux before you use it on a vintage board | Electronics Repairers - Freelance Forum - The Community for Independent Professionals

Blair Mason · 2026-06-17T13:35:03.783928+00:00

I wasted 3 hours and ruined a 1970s Marantz receiver because I grabbed a bottle of flux that had gone bad. It was sitting on my shelf for maybe 4 years and turned acidic, ate right through a trace. Cost me about $80 in parts to undo the damage. Anyone else ever get burned by old flux or am I the only one?

scott.alex4mo ago

Learned that lesson the hard way too, test strips now live in my tray always.

3

kevin_williams4mo ago

Check your flux's pH with a cheap test strip before using it on anything valuable.

2

craig.parker4mo ago

Yikes, that pH strip tip is actually pretty smart. I never would have thought of checking that, but it makes total sense for old gear. Might start keeping a pack in my tool drawer just for peace of mind.

2