Prob with 4x20 lcd: blank screen...

Question · 10-11-2001, 02:18 AM

Well I just got my 4x20 backlit lcd from eio.com...and I just soldered it using eio.com's schematic combined with this page: http://www.geocities.com/krebnarb/lcdguide2.htm ...but it doesn't seem to be powering up correctly. I should be seeing 2 bars, but all I notice is when I turn on the computer, I notice the backlight lights up ever so slightly...only barely noticebly. I checked my connections and soldering...I'm not worried about the parallel port (yet) as I want to get the power prob fixed first..

Any suggestions? I have followed the schematic except that (as per the above site's instruction) I replaced the 100 ohm pot with a 10 ohm resistor and got rid of the 10k pot (so pin 15 on the lcd aka VE goes to the 5V).

I'm stumped. Any help is seriously appreciated.

Raas · 10-11-2001, 03:17 AM

Quote:

I have followed the schematic except that (as per the above site's instruction) I replaced the 100 ohm pot with a 10 ohm resistor and got rid of the 10k pot (so pin 15 on the lcd aka VE goes to the 5V).

I Think there's the problem..
I have a 4x40 and it really needs the 10k pot
otherwise you won't have control over the contrast.
When I turn it to zero resistance, I won't see anything on the display, I have to set it all the way to 10k to see the characters on the display.

Put in a 10k pot and use it all the way,
should solve your problem.

Hope this helps you out.

Greetz

Question · 10-11-2001, 04:36 PM

ergh...I put the 10k pot back in the mix...but I still get the same results..here's what the schematic looks like now..

Any ideas?

Question · 10-11-2001, 10:42 PM

ARGH! I replaced the 10 ohm resistor with a 100 ohm pot so that I followed the schematic exactly...but it still doesn't work...when I turn the resistance down on that pot, the screen turns completely orange...so I know it's being powered...but it's still blank. When I turn the other knob, nothing at all happens. Help?