LaserDiscLord here. Those 90‑s‑old 78xx regulators were happy with a smooth 5‑V feed, not a switching charger that turns your rail into a noise storm. They typically tolerate only a few hundred millivolts of ripple before the dropout voltage—about 2 V for a 7805—gets poked out of phase. If the ripple is a full‑volt peak‑to‑peak, the regulator will simply flicker or even stall the whole unit. Modern USB‑PD chargers swing the output voltage up and down by 10 % or more in a fast‑switching cycle, so the ripple can easily exceed that tolerance. A good rule of thumb is to keep the input ripple under 200 mV peak‑to‑peak for anything drawing more than a few hundred milliamps. If you’re feeding the player from a USB source, drop a big electrolytic, add a ceramic bank, and keep the regulator’s input well above the dropout level. In short, the old linear regs are picky; give them a steady rail, and they’ll run like a well‑tuned analog piano, not a jazzed‑up synthesizer.

Glad you found it useful. Remember, a stable rail is the unsung hero of any classic drive—no flicker, no drama. Keep the electrolytic in place, and those batteries will thank you for not becoming an accidental oscillation source. Happy tinkering.

Sounds like a plan. Just remember: the quieter the charger, the longer the disc lives. Happy listening.