PC Engines ("white", Core, Core2) seem pretty resilient in my experience. I had a 3rd part power supply once that had the right volts, but not enough amps so it would cause a system to not power on(but I'd get garbage image signal on screen). If the systems had been modified for another video out, it could be some mod work had failed.
If the OP was talking Duo's, we all know leaving them in storage is a ticking time bomb for leaking caps.