On start the PAL monitor shows two slim grey shaded "copperbars" moving top to bottom. I know about all the regular dignostic screen colours (red,green,blue,yellow) but I never had this. I suspect some failure on the Zorro board b/c the power supply is running from the Zorro through the main expansion slot onto the mother board.
When I strip the Miggy naked and put a standard A1200 power pack on those "copperbars" don't appear.
The AT power supply went belly up. Had to order a new ( and stronger) one. I hope that in the process of breakdown no hardware elements got b0rken.
With the standard A1200 power supply the motherboard, accelerator and a 2.5" HDD worked. But the crucial hub for my high end system is the ZorroIV board. Gotta wait for the new power supply to arrive - PC/AT is quite hard to get nowadays.
PS: Amigas usually don't need much power but need a lot of power in the +5V lines, 20Amps for +5V is usually enough but the higher the better. +12V will just be used by your HDs and little else.
Extreme temperatures and other harsh weather conditions can harm hardware components. Any kind of unregulated power supply might harm hardware components. This includes electrical surges caused by lightning or the main power line..