Accuphase A75 Voltage conversion 100v-230v

Based on your posted images, from left to right on the quick connect terminals, voltage conversion wiring as below:

100V 1 = orange, 2 = red+brown, 3 = yellow, 4 = white+grey, 5 = empty

230V 1 = orange, 2 = red, 3 = grey+yellow, 4 = white, 5 = brown

I highly recommend connect a Dim Bulb Tester or an 300watt incandescent light bulb in series to power up the amplifier after voltage conversion. If anything goes wrong, the bulb will simply light up instead of dim down to prevent damage of the amplifier.

Just for your reference, this is a image of A-70 wired for 230V mains voltage, I believe the A-75 should be similar.

Thank you for the comment! I have a question. Based on the measurements of the inductance for each line, the following correlation was observed. Both the yellow and orange lines had a resistance of 3.5kΩ, which corresponds to 115v. Similarly, the brown and red lines had a resistance of 2.6kΩ, indicating they are intended for 100v. With this in mind, looking at the wiring in the photo of A70, it appears that the red (100v) and yellow (115v) lines are in parallel, suggesting a total of 215v. Following my line of thought, I assume that combining the orange (115v), gray (0v), and yellow (115v) lines would result in 230v. The orange line in the photo connects to a white line coming from a board with a relay. I believe it should be fine to replace the orange line with the red one, which is rated for 100v, according to my understanding. Would there be any issues if I were to swap the orange line with the red line based on my assumption? Also, I would greatly appreciate it if you could explain the significance of the white line coming from the board with the relay. With respect, 

My previous post was based on your measured result:

I have already measured the resistance allocation of the main transformer wires using an LCR meter.

https://drive.google.com/drive/folders/1jEZNpgb04ZSw6yBU3Tum0yNrq4RdXZ6P?usp=sharing

1. Orange - 120V Red - 100V Grey - 0V

2. Yellow - 120V Brown - 100V White - 0V

I should have been more specific:

100V 1 = orange, 2 = red+brown, 3 = yellow, 4 = white+grey, 5 = empty

120V 1 = red, 2 = orange+yellow, 3 = brown, 4 = white+grey, 5 = empty

220V 1 = orange, 2 = red, 3 = grey+yellow, 4 = white, 5 = brown

240V 1 = red, 2 = orange, 3 = grey+yellow, 4 = white, 5 = brown

As you can see, there's actually no 230V setting! Depending on your country, you can set it to 240V (UK) or 220V (China).

I believe it should be fine to replace the orange line with the red one, which is rated for 100v, according to my understanding.

Yes, this should not cause any problems.

I would greatly appreciate it if you could explain the significance of the white line coming from the board with the relay.

It provide the required power to the soft-start board.

When the power switch pressed in, mains voltage applied through two sets of ceramic resistors paralleled (J1,J3 in place for 100V/120V) or in series (Remove J1,J3 install J2 for 220V/240V) in order to reduce inrush current.

After a few seconds, the relay turn on and bypass the soft-start resistors.

I successfully changed the voltage of the A75! Thank you! Now, I will attempt to change the E380 to 230V. I have experience converting to 115V in the past, so I have a rough idea. Based on the photo of the power board, J1 and J3 correspond to 100V, J4 and J5 correspond to 115V, and J2 corresponds to 0V. In this case, for the 115V configuration, I will move the jumper from J1 to J4 and from J3 to J5, and that should be sufficient.

https://drive.google.com/drive/folders/1dVlrJMGQGBO0BtF7u9xi2Ras_xYSasM0?usp=drive_link

For the 230V configuration, I anticipate that by moving the jumper from J1 to J4, removing jumpers from J2 and J3, and adding a jumper to J6, the transformer circuit will be parallelized for 230V. I will also change the fuse to 3.15A, and then I'll be finished.

Regarding E-380 not having a soft start circuit or relays, could this be because the inrush current is not significant? Please provide advice.