Spent 4 hours chasing a ground loop on a 1980s Marantz receiver that ended up being a single bad solder joint

Pulled my hair out for half a day on this one. Had a low hum that got louder with volume, checked all the caps, swapped transistors, even rebuilt the power supply section. When I finally broke out the oscilloscope and traced it back, it was a cold solder on the ground pin of the tone control board. 10 seconds with an iron and it was gone. Has anyone else spent way too long on something that simple?

2 comments

2 Comments

uma_reed2614h ago

oh come on, four hours on a ground loop is practically a speedrun for vintage gear. you learned way more chasing that ghost than you would have if you found it in ten minutes. that cold joint taught you more about circuit topology and signal paths than any schematic ever will.

piper17511h ago

Cold joint taught you about bad solder joints, not circuit topology, @uma_reed26.