Screen blank when tryin to play game I cant see anything i get sound but no picture onthe screens

Quick answer - not specifically to change font size, but to change whole screen size
The whole screen size can be magnified (zoom in) by simultaneously pressing CNTRL + ; the reverse operation (zoom out - what you want I think) is performed by CNTRL - (press cntl and + keys simultaneously)

Or change (increase) the resolution of the screen by right clicking a blank a blank area of the desktop and selecting 'screen resolution' in Windows 7 or in XP one the tabs similarly labeled, and increasing resolution if not at max already.

12.February.2015

I have the same problem whit my plug & play and i dont now what i have to do please help me

Please replace inverter board

Try removing the battery or reseting the unit if there is a reset button. Otherwise it sounds like the screen died.

your graphics processor IC chip needs its solder joints reflowing, and the heatsink re securing.

This will solve the problem.

Regards

FixMyConsole

If you can still hear sound make sure your video output is compatiable with the setting on your tv example dont try to put 1080i if your tv can only run 720i

We had the same problem with ours. We had to call XBox company and we ended up shipping ours off to be fixed.

try on other tv

start with this
http://www.fixya.com/support/r561901-ipod_problems_start_5_solutions

if TV have black screen,increase screen control to see vert amp IC is defective if you see one horizontal line in picture tube screen,and if screen is white with lots of line acrose ,you can find open resister,on picture tube board,or in main board near HV transformer.