Help with JC-20JT power please

[BolanAudio]

Hi everyone! I just wanted to double check my logic before I accidentally blow up my amp.

My dad gifted me a Japanese Roland JC-20JT for Christmas. Because I live in the US, I thought I was going to have to swap the transformer but once I opened it up I found that both the transformer and the board were marked 100v/117v. So I shouldn't need to do a transformer swap, right? Or am I missing something? I will still be swapping out the 2 prong japanese power cable for a 3 prong.

[g1]

Usually there are still some adjustments need to be made, like moving some jumpers on the board, or using different wires on the transformer.
It's possible they designed it to work for both voltages as is, but our modern line voltage is a lot closer to 125V rather than 117V.  So there is a danger of some components being subjected to voltages that are too high for them (the first thing I would be worried about would be the main filter capacitors).
I tried to find a schematic or service manual but there doesn't seem to be any readily available online.  That would show if there is anything that needs to be changed internally to run on North American line voltage.

[BolanAudio]

Dang, well there goes that idea. Any advice as far as transformer selection? While running it at 100v I measured 13.10v where the transformer meets the board.

[Jazz P Bass]

( I found that both the transformer and the board were marked 100v/117v.)

Can you upload a pic of the transformer & board markings?

[BolanAudio]

Here you go!

[g1]

Can you show where the red and black wires from transformer are going?
If it were not adjustable I would only expect 2 wires on the transformer primary.
Or maybe the blue/white/yellow is the primary side.  Show where those go on the board as well.

[Jazz P Bass]

What does it say under the Ylw & Blu wires?
Attention something.....

[BolanAudio]

I believe the white/yellow/blue is the primary as the are connected near the power cable and the red/red/black are the secondary as they are connected near the bridge diode and filter capacitors.

Heres how they are connected in case you cannot see in the pictures.

T1 GND - Not connected
T2 GND - Not connected
T3 AC IN - Black wire from power cable
T4 AC IN - White wire from power cable
T5 COM - White wire from transformer
T6 PRI - Blue wire from transformer
T7 NC - Yellow wire from transformer
T8 BLK - Black wire to transformer
T9 RED - Red wire to transformer
T10 RED - Red wire to transformer

The english version of that message says CAUTION for continued protection against fire hazard replace only same type fuse(s)

[Jazz P Bass]

I have taken snips of the wiring for other JC amp transformers.
Unfortunately, there are no wiring colors.
On your setup:
Primary
T3 AC In (Blk)
T4 AC In (Wh)

T5 Common (Wh)
T6  ____         (Blu)
T7 _____         (Ylw)

Secondary
T8 (Blk)
T9 (Red)
T10 (Red)

It appears that T5 & T6 /T7 is the clue.
If you can, disconnect T5,6 & 7.
Either T6 or T7 is going connect to AC Hot, the fuse.
If so, it may be as simple as swapping T6 & T7 on the board.