Friday, July 2, 2010

Apple IIc plus 240V modification revisited

In the previous modification I essentially followed Jorge's mod:
and adapted it with locally available parts.

This has one big drawback. It generates a lot of heat. It is also very inefficient. The voltage is dropped down by letting it go as heat. With the case closed, it may (I did not want to try) be possible to reach a temperature that can warp, deform, or quickly yellow the area of the case near the power supply.

I thought about modifying the switching power supply the "proper" way, but without knowing the actual design of the original supply, plus my limited knowledge of switching power supplies, I thought this may not be the way for me to go.

James Littlejohn have made a lot of adaptors for ATX power supplies for use with Apple II's. One of the items he has is the LittlePower IIc+. This handy device, plus a small enough ATX supply should be enough to run the IIc+ with no problems.

After waiting a few weeks for the USPS to deliver my mail, I finally got all the parts I need. Earlier today, I opened up the IIc+ to to a quick test:
After getting it to work, I proceeded to taking the power supply and the power brick apart:

As you can see the power brick is way smaller than the original power supply. This will fit nicely into the original metal shell, and still have room for the LittlePower IIc+ and the picopsu.

Now it's time to wire the picopsu directly to the power brick. Note that I have kept the shell and all the parts in case I want to put it back together. Or in case I decide I want to turn the IIc+ into a portable device with battery, etc built in. There is a grounding board at the bottom of the unit, it wasn't too hard to desolder this:
This is the actual board of the power brick. The AC goes into the 3 big pads near the right side:
Unfortunately for me, the LittlePower IIc+ doesn't fit into the metal shell in its intended location over the hole. It must have been expected that you will be removing the internal power supply to use this device. If I remove the power supply, there will be nothing to hold the switch and the IEC connector at the back. I thought that maybe I could extend the connector with some wires:
Ok looking good.
After putting electrical tape on the parts that can potentially touch the case, including the ATX pins, I am now able to close the case: (if you look carefully you can actually see the green LED of the power brick when the unit is on)

Finally I can close the whole case:

Run a short Applesoft program:

I have left both apple keys held down to run a continous self test. So far it's been 3 hours and I don't feel too much heat (next to none) out of the power supply. I may or may not revisit this yet again. I might decide to power the unit with batteries. There is still room on both sides of the 3.5" floppy drive for other things so maybe I may be able to leave the brick internal.