Change the expand collapse(open, close)icons

[PS]

I wanted to change the default triangular icons to +,- symbols. I
tried so many ways but nothing worked.I have been sitting with this
for the past 2 days.Below is the sample code. Somebody please help
me!!

Should i make any other changes to the css or js file?

"themes" : {
"theme" : "default",
"dots" : true,
"url" : "/EPDA/themes/default/style.css"
},

"types" :{
"types":{
"doc":
{
"icon":
{
"image":"images/file.png"
}

},
"parentFolder" :
{
"icon" :
{
"image":"images/foldericon.png"
},
"icon-open" :
{
"image":"images/minus.png"
},
"icon-closed" :
{
"image":"images/plus.png"
}
},
"childFolder" :
{
"icon" :
{
"image":"images/foldericon.png"
},
"icon-open" :
{
"image":"images/minus.png"
},
"icon-closed" :
{
"image":"images/plus.png"
}

}

}
},

[vakata]

Hi,

The +/- icons are handled from the theme ... so you may want to try
the classic theme, or simply edit the default theme, and save it as a
new one - open the d.gif and d.png files and replace the triangular
icons with whatever you need :)

Kindest regards,
Ivan