i have a xf7 that works fine but the display only has backlight. last month it would boot up to the opening screen then go to 1 sound setting by itself .it would not make sounds but the display was showing that it was good. i noticed on one board a few capacitors that had expanded. i ordered them and replaced them,now the xf makes sounds and all the buttons work.But, now i have no display? do you think the display just went bad or the board that feeds it info?? i believe its a YC405. any ideas or help would be great!

strat1953 - 03 September 2018 08:58 PM

i have a xf7 that works fine but the display only has backlight. last month it would boot up to the opening screen then go to 1 sound setting by itself .it would not make sounds but the display was showing that it was good.

If the boot process seemed normal, the usual cause of no sound is that Local Control has been turned off.

 

strat1953 -

i noticed on one board a few capacitors that had expanded. i ordered them and replaced them,now the xf makes sounds and all the buttons work.

Which capacitors did you replace?

 

strat1953 -

But, now i have no display? do you think the display just went bad or the board that feeds it info?? i believe its a YC405. any ideas or help would be great!

Before doing anything else, check the adjustment of the rear panel LCD CONTRAST control. If turning that through its range doesn’t help, make sure it wasn’t damaged during servicing.

Otherwise…
A common cause of problems when servicing a Motif XF6 or XF7 is hinging the top panel open more than 90 degrees. That can lead to damage to interconnecting cables and/or the connectors themselves.

I suggest that you carefully look over cabling that might have been stressed while you did the work. YC405 doesn’t identify the board. The XF Service Manual is available here:
https://elektrotanya.com/yamaha_motif_xf6_xf7_xf8.pdf/download.html

the caps i replaced were on the far left pc board. the board just below the display is the one that has the yc # on it. the display has a small ,maybe 3/4 inch ribbon cable that plugs into this board thru a white ribbon cable. the sounds and functions all work. just no display. im trying to determine if its this board or the display that went bad? any way to test the display? with an ohm volt meter? the lcd control is good

The LCD data originates on the DM board, and is passed through the LC board to the display itself. Problems could be with any of those, or the interconnecting cables.

Did you download the service manual? I provided the link so that you could identify board nomenclature, etc. The YC405 designation isn’t particularly useful, since the manual will mostly refer to that as the DM board.

I would start by looking at voltages and data lines (with an oscilloscope) at CN203 on the LC board. See page 236 of the SM. Verify that the CONT pin voltage changes when the CONTRAST control is turned. By the way, the display is a Kyocera KCG507QV1DB-G070.

thank you.looks like a bad dm board.im looking for a used one