Problem Refresh Grid Object using AJAX

I'm with problem in Grid object. Built a Grid dinamic refresh, thus with filter using AJAX.
Seem work fine, but when I selected any row for to execute query over, on refresh grid the scroll-bar don't back on begin.

I tried to use..

obj.raiseEvent("adjustScrollBars");
obj.raiseEvent("adjustScrollHeight");
obj.setCellModel(table);
obj.refresh();

Any help would be greatly appreciated.