Help with a display on a yamaha sound equipment - Page 1
Forum section: electronics / repair

author: YTSOC
author_rank: Contributor
timestamp: July 25, 2017, 05:22:44 pm
content: So basically the display is showing all the pixels on(graphical lcd)the service manual ishereso the chain is this: cpu- lcd-driver that has sme static ram and lcd modulei've changed the lcd controller and the lcd module but nothing changed, could it be the static ram of the lcd controller?

author: Armadillo
author_rank: Super Contributor
timestamp: July 25, 2017, 06:09:52 pm
content: Check the basic, Check power supply,Measure CN6 voltage, Use Pin 9 as Ground Common [black probe],measure Pin 12 with respect to Pin 9,measure Pin 1 with respect to Pin 9measure Pin 2 with respect to Pin 9

author: YTSOC
author_rank: Contributor
timestamp: July 26, 2017, 05:06:33 pm
content: pin 12----9 =5v1----9 = 7.8v2----9 = 9.9vi forgot to mention other than this, the device is fully working, it has sound on the output, the other led segment display works

author: Armadillo
author_rank: Super Contributor
timestamp: July 26, 2017, 05:47:48 pm
content: Quote from: YTSOC on July 26, 2017, 05:06:33 pm1. Are the polarity correct for Pin 1 and Pin 2?2. Is the separate +5D for the backlight available [wire to the backlight]3. Pin 3,4,5,6,7,8,10,11 - Use oscilloscope to see that the signals are alive or use digital logic probe. You have to manipulate some keystrokes to purposely change the LCD display to be able to see the signal changes.If item  Polarity verified -ve, item  +5D OK, item  digital signal alive then the LCD is defective. Change the LCD display (64 x 240 dot graphic LCD) [about US$130 listed price]http://www.yamahamusicians.com/forum/viewtopic.php?t=9146

author: mathsquid
author_rank: Frequent Contributor
timestamp: July 26, 2017, 09:25:16 pm
content: Is is possible that your contrast knob is bad?I was initially thinking that maybe the contrast got turned all the way up, so I checked my rm1x. Turning the contrast all the way up only darkened the display; it didn't turn completely black. Ditto when the LCD is turned to negative mode.

author: YTSOC
author_rank: Contributor
timestamp: July 27, 2017, 03:58:00 pm
content: i don't think the contrast adjustment is badI've probed some pins and it doesn't look good: on pins that i do have some waveforms they are static except one, don't change when i press buttons that i asume change things on the screenhere are some results:XD0-XD3-- No waveformsLP approx 4.4khzYD 70hzwf 35hzXSCL about 200khz and this one seems to have some activit (or maybe triggering probems)see video

author: Armadillo
author_rank: Super Contributor
timestamp: July 27, 2017, 05:42:31 pm
content: Yeah! the fluke 125 can see regular clock type pulses but to see the irregular type signals you need to know how to use the "trigger" properly.This is where I say a simple digital logic probe can be useful in repair works and no need to worry about missing pulses.If you can, use the XSCL rising edge as trigger source and single shot mode [a few iteration needed or reversely use one xdata line as trigger source and capture the clock as confirmation in single shot mode]. Or just use a simple digital logic probe.Of-course, those with logic analyser will favour using it.And best to manipulate it to the LCD test screen program so that there are more activity on the pins on the vertical test bars display.If it sounded too complex, just borrow one good LCD and plug it in.The LCD is without DC to DC generator and without controller. For such a simple LCD, wonder why it is so expensive!If I will you, I will "Don't just....tear it apart"........Just few latches is it?

author: YTSOC
author_rank: Contributor
timestamp: July 28, 2017, 06:15:06 am
content: from my perspective the problem seems to be on the board not with the lcd, there should be activity on pins XD0-3 or am i mistaken?

author: YTSOC
author_rank: Contributor
timestamp: August 03, 2017, 03:18:31 pm
content: solved, it was the SRAM, soldered a new one and boom i got the screen workingIF anyone is trying to replace the screen on this yamaha RM1X you can put in this display: LM24064BFW