Spent a full day chasing a phantom short on a vintage amp

I was fixing a 1970s tube amplifier that kept blowing fuses. I checked all the usual suspects, caps and tubes, for about four hours with no luck. The real issue was a tiny solder bridge hiding under a wire bundle near the power transformer. My mentor, Frank, came over and said, 'Check where the wires bunch up, that's where they hide.' It took another three hours of careful probing to finally spot it. What's the most hidden fault you've ever found in a piece of gear?

3 comments

3 Comments

jade_jenkins1mo ago

My old man's 1962 Fender Concert had a weird hum that came and went. I spent a week on it before finding a cracked eyelet board under the power transformer, the break was hidden by a blob of old wax. Had to reflow every single joint on that board.

ray_martinez821mo ago

Sometimes the factory itself is the problem, @jade_jenkins. That old wax blob was likely a sloppy fix from the original assembly line. It makes you wonder how many amps left the shop with hidden flaws just waiting to fail.

evan_green521mo ago

That "blob of old wax" hiding the crack is a classic. I've found dried glue or even a big drip of solder can cover a bad joint or a broken eyelet. Now I always scrape away any of that old gunk with a dental pick to really see the metal underneath. It adds time to the cleanup but it's the only way to be sure.