Author Topic: Help with a display on a yamaha sound equipment  (Read 1664 times)

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Offline YTSOC

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Help with a display on a yamaha sound equipment
« on: July 25, 2017, 05:22:44 pm »
So basically the display is showing all the pixels on(graphical lcd)

the service manual is here

so the chain is this: cpu- lcd-driver that has sme static ram and lcd module

i've changed the lcd controller and the lcd module but nothing changed, could it be the static ram of the lcd controller?
 

Offline Armadillo

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Re: Help with a display on a yamaha sound equipment
« Reply #1 on: July 25, 2017, 06:09:52 pm »
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 9
measure Pin 2 with respect to Pin 9
 

Offline YTSOC

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Re: Help with a display on a yamaha sound equipment
« Reply #2 on: July 26, 2017, 05:06:33 pm »
pin 12----9 =5v
      1----9 = 7.8v
      2----9 = 9.9v


i forgot to mention other than this, the device is fully working,  it has sound on the output, the other led segment display works
« Last Edit: July 26, 2017, 05:13:49 pm by YTSOC »
 

Offline Armadillo

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Re: Help with a display on a yamaha sound equipment
« Reply #3 on: July 26, 2017, 05:47:48 pm »
pin 12----9 =5v
      1----9 = 7.8v
      2----9 = 9.9v


i forgot to mention other than this, the device is fully working,  it has sound on the output, the other led segment display works

1. 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 [1] Polarity verified -ve, item [2] +5D OK, item [3] 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
« Last Edit: July 26, 2017, 06:23:12 pm by Armadillo »
 

Offline mathsquid

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Re: Help with a display on a yamaha sound equipment
« Reply #4 on: July 26, 2017, 09:25:16 pm »
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. 

Offline YTSOC

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Re: Help with a display on a yamaha sound equipment
« Reply #5 on: July 27, 2017, 03:58:00 pm »
i don't think the contrast adjustment is bad

I'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 screen

here are some results:

XD0-XD3-- No waveforms

LP approx 4.4khz
YD 70hz
wf 35hz
XSCL about 200khz and this one seems to have some activit (or maybe triggering probems) see video
 

Offline Armadillo

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Re: Help with a display on a yamaha sound equipment
« Reply #6 on: July 27, 2017, 05:42:31 pm »
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?
 

Offline YTSOC

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Re: Help with a display on a yamaha sound equipment
« Reply #7 on: July 28, 2017, 06:15:06 am »
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?
 

Offline YTSOC

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Re: Help with a display on a yamaha sound equipment
« Reply #8 on: August 03, 2017, 03:18:31 pm »
solved, it was the SRAM, soldered a new one and boom i got the screen working

IF anyone is trying to replace the screen on this yamaha RM1X you can put in this display: LM24064BFW
 


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