Here is the link.
Based on the image, I believe the white and blue wire that soldered to the connector block is incoming AC voltage.
1. Power up the C27 with 100VAC, use a DMM to to measure the voltage across the white and blue wire you should get 100VAC.
2. Measure the voltage across white and yellow wires and you should get a reading of 115VAC to 120VAC.
3. If you confirm the above reading are correct, swap the yellow and brown wire on both side of the connector block, so both yellow wires are connected to the blue wire.
4. Done. Voltage conversion from 100VAC to 120VAC is completed.
Success! Thank you! I want to offer some additional information in case something goes wrong. So, I did the test, but I plugged the unit directly into my electrical outlet at home, causing the fuse to blow. In case this happens to you, do not panic, the fix is simple. (If you have an older Accuphase that will not turn on, you may want to check this first because the unit will not power up if the fuse is blown or defective because of age)
1. Remove the fuse connected to the power button (Power plug should be removed and unit turned off)
2. The fuse is a T1. 6AL 250V (simply a 1.6 A 250V slow-burning fuse).
3. You can find replacements here:
4. Simply replace the fuse and the unit will come back to life.
Electrical engineering is not my professional background, but it appears the fuse also acts as protection in case someone effs up and plugs the unit into an outlet with the wrong voltage or uses the wrong jumper combination.
If so, the fuse blows, cutting power off to the unit; therefore, protecting the board from frying. Pretty clever! By the way, I own a converted E600 an A48 and have seen diagrams of the inside, but actually taking apart this unit and seeing it for myself was an experience. I mean, the board and everything is so nicely put together. Makes you almost want to put a frame around it.
So, I did the test using my step down transformer and converted the voltage and remeasured using my DMM. It works! 120V! Thank you!