LCDInfo.com

Hi there,

i need some help with my display. I have tried everything that got in my mind and what I found in this forum, but i can't get it to work.

The name of the display is MGL(S) 240128T. It has a T6963C Controller.

I wired it up like this: Schematic
Here is the Datasheet: Datasheet

The order of the Pins on the Display is a bit different comparing to the schematic, but the names are the same, so it should work going by the names.
Except of Vlc, instead of that one I have a pin calles V0, but according to the datasheet, thats the pin where the voltage for the LCD Driving shall be inserted. I don't have Vee, so I think the Display doesn't have an onboard DC/DC Conterter.

So the negative Voltage comes from an inverter i bought here in Germany at Conrad. I have measured the voltages, and they all seem to be ok.

I have played around with the setting of my LPT, but whatever I do and whatever software I use, nothing ist display on the LCD.

If i put the reset pin to GND, then a line of one pixel height is displayed on the Display, as long as reset is at GND. Is that normal?

But up to now, this line is the only thing I've seen on the display so far, can anyone give me a hint of what i could try?
Thanks a lot!

two ideas:
1. is lcdinfo configurated to the right wiring? (i think you try it to the tweakers wiring)
2. is the negative voltage high (or low or what ever) enough? (i've seen a lcd that needs -20v)

The line while in reset is normal as far as I know and if you can see this line your negative voltage should be fine.

You should still double check the wiring to parallel port to make sure it's ok and then make sure you have selected the same wiring settings in the program. And for the parallel port setting I think many have been succesful with ECP/EPP.

Thanks for the replys.

As Henry said, the negative voltage should be ok.

I measure 17V between V0 and Vcc, that should be fine.
If I play around with the contrast pot, then the line that is shown in reset gets darker/lighter.

The wiring in the programs was exactly like in the schematic.

I will now check the wiring again (I did that, but maybe I was blind ), and if it still doesn't work... well dont't know.

If this line that is shown when in reset is ok, is it then sure that the controller ist ok? I bought the display at ebay, so you never know...

first time i testet my lcd, neg. voltage was too low. on reset you could see the line. so i still think that it might be the neg. voltage.

(i've heard that reset the display too long can kill it. it might be wrong, but i didn't want to test it.)

so, now i have checked my wiring three times, and it is absolutely ok.
been playing around with the lpt settings again also, and none works.
wiring settings in the programs is ok.

now, if the display is ok, then it can really be the negative voltage i think?

i have now found a datasheet that says that the maximum voltage between v0 and vcc can be 30v!

so, how can i generate such a high voltage??

you can try this: http://www.skippari.net/lcd/kontrasti_mc.gif
i think you had to change the 27k and the 5.6k resitor.

I'm a bit late here but it might be the negative voltage then. I haven't had any problems with negative voltage yet so I haven't been playing with it much so I'm not that familiar of all the symptoms it causes.

i've figured it out now.
it really was the negative voltage.
this display needs a negative voltage of -24v, not -12v.
i bought an inverter here in germany from www.reichelt.de, that creates the -24v out of 5v.

the display works now with all programs i tried. thanks for the great help here.

there is only one little problem:
some lines of the display flicker strangely.
it's a bit hard to describe. if i play with the voltage pot, then some lines get dark sooner than others...
hm anybody know what i'm talking about, or got a solution for that?

I have seen similar behaviour on Displaytech 128x64 KS0108 displays but unfortunately I don't really know what to do for it. With the Displaytech display it was mainly looking bad from certain angles.