@ maxpiano69
Hi, that's quite an old model, I think your best chance is to try and ask Ketron directly (or via your country's official distributor) .
Ciao, é un modello davvero vecchio, credo che la cosa migliore per te sia provare a chiedere a Ketron direttamente (o tramite il distributore ufficiale del tuo paese).
Maybe there is a key combination on the TS4 to perform a hard reset.
My problem is that I can't read the Italian manual :)
Could you take a look?
The manual can be found here :
http://www.polynominal.com/solton-ts4-k/index.html