Samsung Galaxy Ace S5839i data:
GSM frequencies :850 900 1800 1900
Standard UMTS :900 2100
Type :Touch
Dimensions (W x H x D) :112,40 x 59,90 x 11,50 mm
Weight :113,00 g
Main display :Color / TFT
16M colors
320 x 480 px (3.50") 165 ppi
Talk time (max.) :2G: 660 min. (11,0 h)
3G: 390 min. (6,5 h)
Stand-by (max.) :2G: 640 h. (26,7 days)
3G: 420 h. (17,5 days)
Standard battery :Li-Ion 1350 mAh
Internal memory :150 MB
RAM memory :384 MB
Memory cards : microSD, microSDHC (up to 32 GB)
Operating system :Android 2.3 Gingerbread
Processor :Broadcom BCM21553
Processor clock :832 MHz
Touchscreen : yes
SAR (10g) :0,616 W/kg
How to hard reset:
Before you start you should know that all data will be lost
If you forgot the combination to unlock the screen follow these steps:
1.Power off your phone
2.Press together volume up + home key + power button
3.Choose with volume buttons "wipe data/factory reset" and select it with home button
4.Choose "yes" with volume buttons and select it with home button
5.Wait untill format ends
6.Choose "reboot"
7.Wait until the phone restarts
That's all
Here is video how to do: