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Accuphase A75 Voltage conversion 100v-230v

Hello, I would like to request advice regarding changing the voltage of Accuphase A75 from its Japanese 100V model to 230V. While I have experience with voltage conversions, this is my first time working on an A75 model, so your assistance is greatly appreciated.

The basic modification plan involves rewiring the main transformer wires in parallel, replacing the fuse with an 8A slow-blow fuse, and changing the relay jumpers from J1 and J3 to J2. I intend to include circuit photos for reference. 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

To achieve 230V, I believe I need to connect Orange to Grey and Yellow together in parallel, leaving White as it is. If you have any advice or suggestions, please share them. Thank you!!

 

yaman5055
yaman5055 OP
5 posts
 

 

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.

imhififan's avatar
imhififan
2,180 posts
 

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 ...

Yes, your jumper settings are correct!

By the way, the two primary windings of 220-240V are connected in series , and the two primary windings of 100V-120V are connected in parallel..

100V = J1,J2 and J3

115/120V = J2,J4 and J5

215/220V = J1 and J6

230/240V = J4 and J6

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

I don't have an E-380 and can't confirm if there is a soft-start board hidden in the chassis. However, transformers with low VA ratings can be operated without a soft-start circuit.

 

 

yaman5055 OP
5 posts
 

I'm sorry! I made a mistake. 230V is connected in series.
I believe that the E280 and E380 amplifiers do not use the lower-model triad transformers, so it seems that relays and soft-start circuits may not be necessary.

eugene81
270 posts
 

@imhififan You're a legend!

imhififan's avatar
imhififan
2,180 posts
 

@eugene81 

Thank you for your kind words!😊

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