johnson.daniel•2mo agoProlific Poster

A weird trick from a guy at the Milwaukee tool show saved a vintage amp

I was at the Milwaukee tool show last month helping a buddy at his booth when this older guy came up with a busted 1970s tube amp. He said he'd tried everything to fix a hum, even replaced all the caps. The guy next to me, a total stranger, asked if he'd checked the ground on the input jack's shield wire. Turns out the solder joint looked fine but was actually cracked under the insulation. We reflowed it right there and the hum was gone. I've fixed maybe five amps since then where that was the exact problem. Anyone else run into phantom hums from bad ground joints you can't see?

3 comments

3 Comments

the_morgan1mo ago

Oh man, that's the worst kind of problem! It's like the solder joint is actively hiding from you, just sitting there looking perfect while it ruins your whole day. You feel like you've checked every single inch of the circuit ten times over. Then some random person suggests the one dumb, simple thing you missed because it was too obvious. It's equal parts brilliant and totally annoying.

shaneb162mo ago

Yeah, it's crazy how often the fix is in the last place you'd think to look. I've seen the same thing with old guitar pedals where a tiny bit of corrosion on a battery contact causes all sorts of weird noise. Makes you check the simple stuff first every single time now.

barbara_baker572mo ago

Wait, you still use batteries in guitar pedals? I thought everyone switched to power supplies years ago. I remember my old boss had a pedal board that ate nine volts like candy. The contacts would get that white crusty stuff and the whole signal would cut out. He spent hours rewiring before he noticed the battery clip was green.