Updated: Sep 19, 2022
So, the other day whilst (admittedly) working in a messy environment, I managed to fry some RAM chips in my C64. The reason? I accidentally plugged in the wrong power supply. My intention (as always) was to use my modern replacement and test the original one properly later, but it only took a tiny slip and I popped in the original PSU connector and (as expected) got a black screen on a previously working computer. This got me thinking about whether in reality, it's ever really worth using an “original” power supply and I came to the conclusion that it isn't. Now as an owner of a couple of modern replacements I can testify to a few things that might justify the investments I made. So, here goes.
First. Commodore 64 power supplies (especially) are not known for their reliability. Of course “back in the day” they did the job pretty well and as expected...but that was forty years ago and during that time the capacitors have often sat around for years and this dries them up. Now, the PSU might still function for a while but eventually one or more capacitors can explode and I can assure you (besides the shock) the smell is unbearable.
Second. Commodore in their wisdom made a lot (not all) but a huge number of their PSU's that can't even be repaired. Due to safety needs, all of the components inside of the PSU are encased in a hard epoxy which means you can't access the interior (literally) without a hammer and chisel. The hard epoxy, I don't fault, as it stops the whole thing from catching on fire so 'kudos' to Commodore for that.. but it does mean you can't just swap the capacitors for new ones. Added to this, working inside (I know from experience) a PSU is highly dangerous so I think we can conclude it's not really a good option.
Third. Old, working power supplies might work well for a time, but if the voltage “spikes” at any point, many of the I.C chips in the machine can easily be damaged. (In my case, it was a couple of RAM chips and many hours of work to find, desolder, socket and replace them). C64 power supplies don’t have “over voltage protection” and it doesn't take much for the delicate chips inside of the machine to fail, due to a voltage spike. (That's why there are so many non-working machines on ebay!)
In the worst case scenario I have seen, an overvoltage issue fried a SID chip and these things are not cheap these days and should if all possible, be preserved for prosperity!
Fourth, new replacements offer so many advantages, it's almost a “no-brainer”. They run cool, they have newer, more reliable components inside of them and most importantly voltage protection (ensuring your machine isn't accidentally “fried”). Other advantages include an OLED display which shows data on how long the PSU has been used, the voltages in real time (so you know it's running correctly) and it also looks super cool on my desktop. Oh, and did I mention most modern replacements are much smaller and can be tucked away nicely.
The C64's big brother (the Amiga) also has modern replacements available which it goes-without-saying, offer all of the advantages already mentioned. Smaller footprint, more efficient, OLED displays, cool running and most importantly voltage protection. The Amiga is of course a completely different machine to the C64 and often a lot of “black screen” issues are caused by a malfunctioning PSU. Furthermore, with the steadily increasing costs of buying Amiga computers these days, it's silly to risk damaging them for the sake of saving a few quid!
I guess, in conclusion, it's a case of adding up the cost versus the utility. Fixing a computer that never should have needed fixing in the first place wasn't the best use of my time and in all honesty when I returned to my modern supply, I did feel somehow more at peace again. It looked cool, it ran cool and I just felt, more comfortable, knowing that my forty year old computer was in the best possible hands and even better, was unlikely to cause any more unnecessary issues.
The only downside is, once you have one for one computer, you'll never want to go back to using other systems with their original supplies. Although the initial cost might seem a little high, I think (without doubt) it's worth it for peace of mind and above all “your safety” and for me, that's just something you can't put a price on.