Changing Input Voltage on a Roland HP107e-RW Electric Piano

Electrical power grids around the world provide electricity to their end users at a handful of different voltages and frequencies. For example, consumer electronics in the USA typically operate on 100-120 V @ 60 Hz while in the UK most everything runs on 220-240 V @ 50 Hz. In addition to the voltage and frequency variations, there are a handful of power cable plug shapes that various regions use too. People generally don’t have to concern themselves with all this information unless they are traveling or moving abroad and taking their electronics with them.

Friends of ours recently gave Katie a Roland HP107e-RW electric piano they had purchased while living in the UK. When they moved back to the USA, they brought the piano and quite a few other items with them that all ran on 230V. To power those items on the US electrical grid, they purchased a step up converter.

This particular model is the HP107e-RW. There are probably several other similar models for which this modification would work.

Instead of buying a bulky step up convertor to run the piano at our house, I wanted to convert the piano to run natively on the US electrical grid. In order to make this possible I needed to do 2 things:

1. Change the shape of the power cable plug from UK style (Type G) to NEMA 1-15 ungrounded (Type A)
2. Change the input voltage from 220-240 V to 110-120 V

Changing the power cable plug was easy. The power inlet on the piano is an IEC 60320 C8. Many of the electronic devices I own use the Type A cable I needed to replace the Type G cable. Swapping out the cable was simple, but that only changed the shape of the plug, not the voltage.

Interestingly, the Type G plug was actually a wrapper around the head of a Europlug (Type C) plug. This was perhaps a cost-saving measure.

A sneaky Europlug hiding inside the Type G plug.

Changing the input voltage was a little harder. Some consumer electronics have little voltage switches next to the power inlet that are easily accessible on the outside. I didn’t see one of those, but sometimes the switch (or jumper) is inside the chassis on the power PCB.

To get a look at the power situation I opened up the top of the piano. That required removing 8 screws grouped in 4 pairs along the top rear of the piano, then sliding the top board forward and lifting it off. There are no wires or other connections made to the top board.

The blue arrows indicate the 8 screws that need to be removed to take the top off the piano.

After opening up the top I found this beefy power transformer staring back at me. There was no super convenient voltage switch, but surprisingly the input pins on the transformer were labeled—an easy solution! The fix was simple…desolder the black hot wire from the 230 V pin and resolder it to the 120 V pin.

The label on the transformer indicates what voltages are expected on the input pins.

CAUTION: Before beginning this surgery, I recommend isolating the transformer from everything else. Unplug the input power cable from the wall oulet AND disconnect the output power cable connector from the main PCB. As with all things electrical, you could kill yourself if you don’t know what you are doing. Be safe! Be smart!

Out of caution I unplugged this cable connector before unsoldering and resoldering the cable to the transformer.

After moving the hot wire to the correct input pin, reconnecting the cable connector to the PCB, reattaching the top board, and plugging in the new power cable the piano fired up perfectly.

Let me know if this helped you. If you fried your keyboard or yourself, sorry, I am not responsible for your mistake. Better luck next time! 😉