Yamaha YPG625 screen shows only vertical lines

The overal sound of yamaha YPG 625 and keys operation are exellent by the price. The only problem I eperienced is the instrument operation under high humidity environment. Under this condition many keys sound loud over others, furter more with no expectation from mucisian. This problems is normal for that model because the music store change my previously YPG625 for the same problem<br /> <br /> Sometime I solve the problem to located the instrument under sun exposure and cover the keys and display to avoid direc sun exposure.<br /> <br /> Another is apply with a hair dryers over the keys. But is very disconform situation, and I dont know if the Yamaha exposed this isntrument under high humidity environment durig the product test. I has a Ymaha very low budged digital piano and Roland controller A33 in the same condition and never eperience problems, only with this model.