Factory reset Does not function

Question edited for clarity.

Try a Factory Reset. Try a power reset first. Disconnect from the mains plug for 15 minutes.

System Reset - Yamaha PSR-S750 Service Manual

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There are two reset methods in the SYSTEM RESET display: Factory Reset and Custom Reset. ... This function lets you restore the status of the instrument to the ...

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  Yamaha PSR-S750 Reference Manual - System Reset

  https://www.manualslib.com > ... > Reference manual
  This function lets you restore the status of the instrument to the original factory settings. ... buttons to enter or remove the checkmark. ... operation for all ...
  
  

hello sir,
THIS IS SOFT RESET; FACTORY MUTE PARAMETERS WILL BE LOADED INTO ... ART, MULTIVERB LTX, No factory reset, remove battery for more than 5 hours. .... KORG, N364, HOLD ENTER AND 7, THEN POWER ON. KORG .... ROLAND, D-550, TUNE/FUNCTION AND MIDI DATA INIT: HOLD PATCH BANK 2,
thanks from: SHAAD GONDEKAR

You don't need to reset factory.
You just need to change the setting of LOCAL CONTROL.
Lets start :::
While holding TONE / SETTING button,press key D#7 at 7th octave (highest octave on the right hand). Then release. That's all.
Then the sound must be heard..

factory reset Procedure.
Turn the keyboard off then press and hold the TONE and FUNCTION buttons while you turn on

Here is the link for the manual - according to it:
Use the TRANSPOSE/FUNCTION button
to perform the system reset operation.

http://support.casio.com/pdf/008/ctk_691_01_e.pdf

Turn the Keyboard off the press and while holding down the [TONE] AND [FUNCTION] buttons power on the keyboard. Wait until all reset is done.

Have you tried a factory reset??

1) Press [FUNCTION]

2) Press [J] 'Utility'

3) Press [Tab>] to select SYSTEM RESET page

4) Use [4V] button to MARK ON all available settings. Use [2V] to select each setting.

5) Press [D] to EXECUTE when all settings are checked.

zoom GFX-8:
The All Initialize/Factory Recall function is a special function
that lets you reset the GFX-8 to the condition in which it was originally shipped. When All Initialize is performed, all settings of the unit including all user group patches are returned to the default condition. Factory Recall can be used to reset only specific user group patches group to the default settings.
1. Turn power to the GFX-8 on while keeping the STORE key depressed.The display shows "ALL-INIT".
• To perform All Initialize, Continue with the next step.
• To perform Factory Recall, Use the BANK UP/DOWN foot switch and foot switches 1 - 4 to select the patch (from a user group) that you want to return to the factory default condition.
2. Press the STORE key once more.
All Initialize or Factory Recall is carried out.
If All Initialize was carried out,
the unit automatically returns to the play mode.
Note that when All Initialize is executed,
the contents of all patches stored by the user will be overwritten (erased).
When wishing to cancel All Initialize/Factory Recall,
press the EDIT/CANCEL key before step 2.
source: ZOOM GFX-8 User Manual.