View Full Version : VGA-Demo destroyed my LCD-screen!

01-22-2008, 07:12 PM
Hi, I was playing with the VGA demo samples and used the following settings
for my LCD-screen (BENQ FP731) and after a couple of hours it burned up.
The settings are the original from the VGA High-Res Text Driver v1.0.spin.

Was I the first running it in this mode and why did it burn up?

H/W: Propeller Demo Board.

··800 x 600 @ 75Hz settings: 100 x 50 characters
· hp = 800····· 'horizontal pixels
· vp = 600····· 'vertical pixels
· hf = 40······ 'horizontal front porch pixels
· hs = 128····· 'horizontal sync pixels
· hb = 88······ 'horizontal back porch pixels
· vf = 1······· 'vertical front porch lines
· vs = 4······· 'vertical sync lines
· vb = 23······ 'vertical back porch lines
· hn = 0······· 'horizontal normal sync state (0|1)
· vn = 0······· 'vertical normal sync state (0|1)
· pr = 50······ 'pixel rate in MHz at 80MHz system clock (5MHz granularity)

·http://forums.parallax.com/images/smilies/skull.gif·Torsten Jansson / Sweden

01-22-2008, 08:34 PM
I'm surprised you got 800x600 to work at all! I tried a few months ago and couldn't find any drivers that worked in 800x600 mode...

I think LCD's prefer to run at 60 Hz. But, yours is supposed to work up to 76 Hz. But, perhaps your settings made it try to go >76 Hz?

Mike Green
01-22-2008, 09:10 PM
I can't answer why your LCD panel "burnt up", but I've used those settings (and that driver) before with a Samsung SyncMaster 21" LCD display and it worked fine.

01-23-2008, 12:43 AM
Hmm, where did you get the panel? Any modern monitor should have no problem protecting
itself against sync rates outside its capabilities. Personally I would take it up with the vendor
and/or manufacturer.

01-23-2008, 12:57 AM
If the monitor is not under warranty, start by tapping it
along its X,Y and Z axis. You can hit most of it pretty
hard, but don't break the glass.

After the tap test, take it apart and press each of the
components directly against the circuit board. Use an
insulated plastic probe (a pen with the ink well removed).

You might need a friend, or a mirror, to see the front
side of the monitor.

If it flickers back into operation, you have a bad solder