For those who want to avoid the bulky (snd sometimes, expensive) transformers there have been various methods to sun the Apple-1 from a switchmode power supply (or several of them). The most efficient way so far was the "direct feed" method which bypasses the regulators on the Apple-1 by adding three wires, see post #33 of this thread:
I never liked the "direct feed" method despite I used on on many of my burn-in rigs with no problems. The issue is that any mistake with inplementing "direct feed" may blow up all the ICs in the Apple-1 instantly. So you can't make any mistake, and if you happen to have more than one Apple-1 clone, some configured for "direct feed" and some for transformers, it's an accident waiting to happen. I have put a red "DC ONLY" placard on all the "direct feed" ones, but what if the placard falls off ?
So I was looking for a better way. Ideally, if you had a switchmode power supply making +8V and +/-15V output voltages, you could connect that to the J1 power connector of the Apple-1 with no mods to the motherboard, and it would work.
Alas, such a power supply does not exist off the shelf. Certainly, a company like "Mean Well" would make you a customized version which would make the required voltages, but only of you order lots of them. So, no deal.
However, closer inspection of the Mean Well PT-65 shows that it could be hacked to produce the required higher voltages so it could feed the Apple-1 via the on-motherboard rectifiers and regulators. Alas, this hack also requires swapping some of the electrolytic capacitors on the low voltage side against similar ones having a slightly higher voltage rating. These typically are glued to other components by means of a sort of nasty goop. So they are difficult to remove. No mods are done to the line voltage side.
I have been running an Apple-1 using this modified PT-65 for a while now with no problems.
This said, now there is yet another way to run an Apple-1 from a switchmode power supply. I still wonder if anyone would want to do this (is there a real need for yet another power supply solution ? Are people too scared to hack evil switchmode power supplies ?)
So, comments invited ! Tell me your opinions !
- Uncle Bernie