Roland Xp-80 LCD Contrast

4 Jul 2012, 01:10

Hello everyone
My Xp80 was recovered from a failure in (negative) voltage in its main-board. now it works but still has a problem. The LCD contrast is too low. When I set the LCD contrast to 10 (maximum) the characters come visible but they are still too pale or dimmed.
So far I have changed the LCD contrast Capacitor (50v 1uf) but it didn't help.
Can you guys give me a suggestion on this?
Thank you
Ciro

Re: Roland Xp-80 LCD Contrast

4 Jul 2012, 12:44

kooroshi,

First, please do the following test:
Disconnect the wire on pin number 4 of connector CN9 (the one that goes to the LCD) and connect this wire to the GND and see if the contrast is improved.
Let me know about the results.

Cesarsound.

Re: Roland Xp-80 LCD Contrast

5 Jul 2012, 01:54

Thank you Cesar sound for your swift reply.
I removed the R112 (100R) and connected the pin4 of the LCD directly to the GND bypassing the contrast circuit but it didn ' t improved the contrast at all.

Re: Roland Xp-80 LCD Contrast

5 Jul 2012, 09:58

now put a multimeter (in DC scale of 2V) on gnd and pin 4 of CN9 and try to adjust the contrast. confirm if you can read a value aproxmated of -0.9 to + 1.5v.

Re: Roland Xp-80 LCD Contrast

5 Jul 2012, 14:42

The voltage varied from -5.8V to -9V when I changed the contrast from 0 to 10.

Re: Roland Xp-80 LCD Contrast

5 Jul 2012, 15:44

It's completely different from what you mentioned!
Is that bad? I mean the difference is drastic; could this be harmful for the LCD unit?

Re: Roland Xp-80 LCD Contrast

5 Jul 2012, 21:17

Not necessary the LCD was damaged. But certainly the contrast circuit composed by IC6, R106, R108, R107, R114, R113 is not working correctly as the normal contrast voltage of a LCD is about -0.9v to +1.5v, these are the values I found on my XP50.

In my XP50 the problem was on caps AND also on one PCB wiring that was opened (corroded) by acid that leaked from the electrolytic caps. Check the conductivity of all PCB wirings on the circuit that controls the contrast (around the IC6B).

I recomend you read my tread about this problem, you can find useful hints here:

http://forums.rolandclan.com/viewtopic.php?f=50&t=33500

Cesarsound.

Re: Roland Xp-80 LCD Contrast

6 Jul 2012, 06:32

Gracias muchisimo Cesarsound.
I read the posts in the link you provided and tried anything. Now I have come down to this result that maybe IC6 is damaged and is not functioning properly. What do you think about this? Is that possible for a OP-AMP IC to be damaged and partially functional? I'm asking this since the output voltage of this IC is pretty much different with what it should actually be.
Regards

Re: Roland Xp-80 LCD Contrast

6 Jul 2012, 10:28

I suggest you do a external control of contrast using a potentiometer to confirm that the problem is on LCD or not.

Get a 100k pot, connect one of extremes of pot to -5v and other to +5v and the center of pot connect to the wire 4 that goes to the LCD (you should disconnect this wire from the motherboard) and try to adjust it. If the LCD does not responds, you should replace the LCD.

Disclosure: Please note that I do not have the XP80, I am refering only about the service manual and the the problems that I had with the XP50, that btw is quite different in terms of LCD display. And all the tips you can do by your own responsability, because sometimes something can go wrong and damage even more your XP80.

Cesarsound.

Re: Roland Xp-80 LCD Contrast

7 Jul 2012, 14:32

Replacing the LCD contrast driver IC solved the problem. Now the Contrast is adjustable on all the 10 levels. The maximum voltage on contrast level 10 is -12V. Looks like the bad chip was preventing the negative voltage to reach up to this level.
thank you again Cesarsound for your attention and of course for the tips.
Cheers

Re: Roland Xp-80 LCD Contrast

9 Jul 2012, 08:39

great news!

Re: Roland Xp-80 LCD Contrast

10 Jul 2019, 20:45

Kooroshi,

I’m having the same issue with my XP-80. Can I know what IC number is responsible for the LCD contrast?

Thank you,

Eric

Re: Roland Xp-80 LCD Contrast

28 Sep 2019, 16:35

Hello Eric,

It is IC6 located at the underside of the main board. (See XP80 Service Notes).