After almost 30 years the power supply of our Amigas can rightly no longer make it to turn on the computer! Before their death occurs in the worst way, it could be the case to overhaul it, or if it has already given up, the opportunity to make a qualitative leap is more than excellent.
The changes to be made to improve the operating conditions of a Commodore Amiga 4000 are not many but must be made with some care to obtain a good result. I personally believe that improving the ventilation in the case of the 4000 can contribute to an improvement in the functioning of the electronics especially in the presence of accelerator cards and expansions on zorro slots.
To achieve a good ventilation improvement and an overall lowering of the noise generated by the ventilation, I removed the perforated metal barrier that gives on the fan of the power supply, thus leaving the hole open for the entire diameter of the fan. So to protect the fan I inserted an external chrome grill. Instead of the screws I opted for the rubber plugs thanks to which I was able to fix both the fan and the external grill.
The obsolete electronics of the power supply has been replaced with the electronics of a new generation mini ATX power supply (2020) brand new with maximum peak power of 500 Watts and continuous power of 350 Watts. The manufacturer Vultech also supplies a mini ATX version with 600 watts peak and 400 watts continuous. Having updated my Amiga with SATA perfieriche thus eliminating the annoying IDE cable, I opted to leave the molex / sata connectors present in the power supply and replacing the old original wiring, in this way I no longer needed the joints to adapt the connection of power supply from 4 pin molex to sata freeing up more space and leaving the final wiring tidier.
The 3.3 Volt output voltages have been left isolated inside the case, the electronic ignition has been welded to the ground internally letting the original mechanical switch to turn Amiga on or off as conceived in the Golden Age.
To fix the new electronics with reduced dimensions it is necessary to apply at least one small hole in order to guarantee the mechanical stability of the electronics to the power supply case. The hole must be flared to allow the head of the screw not to protrude above the surfaces of the facade of the case because the side in question is in contact with the base of the Amiga case. The combination of the electronics on the rear side with the exhaust air slots allows more than enough space even for fans of classic thickness.
The connection of the output cables from the ATX power supply to the Amiga power supply requires to join the original cables with the new ones without obviously making errors in the correspondence of the colors because an error here would result in incalculable damage to the Amiga MainBoard! The voltages must absolutely match in the correct pins. The joints must be welded and insulated with heat shrink tubing. I prefer to splice the cables rather than go to unsolder them from the board of the new power supply and then weld on the ones I need, in this way I avoid potential damage to the new electronics also I think it is much less demanding to make the joints than to weld the cables on the card.
To replace the electronics with the new one, you can opt for Vultech mini ATX power supplies GS-500M models with 500 Watt peak and GS-600M with 600 Watt peak or for the more expensive 400 Watt SFX Power 2 produced by Be Quiet ! The electronics can be placed inside the case of the original power supply without problems thanks to the small size of the mini ATX format and you can also choose the positioning at your discretion.
Note and clarify that the total power supplied will never be that available for our Amiga due to the fact that the 3.3 volt power lines will remain isolated and unused therefore that hundred watts or less will remain unused. Despite this the 4000 itself does not have a full-bodied absorption, from research done on the web I read that the absorptions are around ten Ampere for the +5 Volt and 6 or 7 Ampere at +12 Volt, considering that the other voltages are all well covered there should be no problems but the same goes for a "smooth" Amiga 4000. In my case, the "weight" of the CyberStormPPC and of the ZZ9000 with XSurf100 and USB module slightly balances a solid state disk instead of replacing the classic mechanical disk. I have not measured the absorption but the power supply with the 4000 at full speed is hard to heat the case, so I am satisfied.