As a 57 owner — no expert, but I worked inside a dozen of them — I urge you to send your Grandson and his "popping noises" to rehab. It takes so little to damage the panels, especially the treble below 100Hz. Even way back when I had mine (over 25 years ago) repairing such damage was nearly impossible, but now...?
It's not just the diaphragms that "arc and burn": so do the stators. Diaphragms are just Mylar; making them conductive is possible but hard work, and getting them 'right' even harder. But repairing the stators? The voltage is 1,500V and the arc may re-strike on each half cycle of the current. The stators don't burn in a brief flash like the ultra-thin film, they can melt: they aren't made of steel. I had one treble panel that looked like third-degree burns on skin, both sides melted and bubbled-up like mozzarella in a too-hot pizza oven.
I assume you use the limiter circuits. But with the aging of components in both the Quads and amp, I'd still be wary. Eternal Vigilance (and fear) is the price of 57 ownership.
It's not just the diaphragms that "arc and burn": so do the stators. Diaphragms are just Mylar; making them conductive is possible but hard work, and getting them 'right' even harder. But repairing the stators? The voltage is 1,500V and the arc may re-strike on each half cycle of the current. The stators don't burn in a brief flash like the ultra-thin film, they can melt: they aren't made of steel. I had one treble panel that looked like third-degree burns on skin, both sides melted and bubbled-up like mozzarella in a too-hot pizza oven.
I assume you use the limiter circuits. But with the aging of components in both the Quads and amp, I'd still be wary. Eternal Vigilance (and fear) is the price of 57 ownership.