I have one of these (Yamaha PSR-S900 Arranger Keyboard Workstation) and after 7 years, the display started going defective – half of the screen was duplicated, lines running through the middle of the display.
This renders use of the keyboard relatively impossible (because there is still a composite video out that can be sent to a portable DVD/LCD player, which will still work for the purposes of reading what’s on the display – your patch selections, mixer settings, scoring, sheet music, file selections, etc.)
I hit eBay and found a few replacement display units for about $150 (shipped from China, but made in Japan), and figured it would be worth trying (after all, a new PSR-S950 still runs about $2000.)
The replacement looks like this:
There’s a single pair red/white power lead with a small white modular plug used to connect it to the high-voltage power daughterboard. (my plug had one fewer white connections, so I used a modeling knife to trim off the extra middle connector).
The display itself connects via a 10-wire flat ribbon connector that is press-fit into the LCD’s connector. These are the somewhat fragile, but when carefully removed, basically easily re-inserted into the same receptacle (similar to re-wiring a video game console mod.) In the photo, this receptacle is on the right-center side of the display.
Since I didn’t happen to have the service manual, we dive in with the screwdriver (all phillips-head). Flipping the keyboard over and laying it on a mattress (to avoid scratches,) you’ll find 14 3/4 inch panel screws, 4 slightly longer 1-1/2 inch panel screws used in the center holes of the keyboard, and about 24 larger headed 1-inch panel screws connecting 2 wood panels to the speakers and bottom frame. You get to remove ALL of these to get the bottom and top shells separated (just keep them in separate dishes/jars.)
The bottom assembly sort of resembles this view from a PSR-1500 (for general reference – the PSR-S900 is more symmetrical in design) The larger screws are connecting the bottom boards to the 2 speaker enclosures and then attaching the wood panels to the bottom plastic shell; the smaller screws go into those taller pyramid-looking tower holes in the bottom case:
This is an interior view of where the LCD is actually mounted (underneath the front panel; this view is of the bottom of the top half of the keyboard):
To access this view, you will be removing the 6 mounting screws holding the CPU board box (the large aluminum vented box sitting on top of the LCD panel area.) There are grounding wires on 3 sides of this box that are simply attached with more of the small panel screws. You can either remove the screws that attach the box to the mounting posts, or the screws that hold the posts to the top assembly (whichever ones you can access most easily.) The only connections I removed to access the LCD were the ethernet cable plugging into the CPU box, and the 2 white multi-wire connections that plug into the back-panel connector board (the one that has the USB plugs, video connectors and MIDI In/Out – it’s mounted to the top (silver) case assembly):
Once the CPU box is unmounted and moved aside (untaping the wires that are taped to the box), you can usually access the first 2 (of 4) screws mounting the LCD to the front panel (these are the 2 closest to the keyboard.) You can remove just the screws attaching the LCD to the aluminum mounts (you do not need to remove the mounts themselves). To access the other 2 (the ones towards the back panel), if you don’t have a right-angle screwdriver that can fit under the back-panel connector board (about 1-inch clearance), you can remove the 6 screws holding the connector board to the top case assembly (4 of these have bendable wire tie-downs on them; the other 2 seem to hold the mylar foil shielding tabs.) There is also a single screw that connects the coaxial video connector to the back panel that must also be removed to move the board.
Inside my particular model (which might have been an earlier build than the one my replacement LCD was designed to fit) the high voltage board was connected with a longer set of leads to the defective LCD. So I unmounted it, rotated it clockwise 90 degrees to move the connector closer to the LCD, and re-mounted it using a single screw to hold it in-place again.
After un-mounting the defective LCD, I removed the existing ribbon connector and before mounting the new one, re-attached the ribbon into the new LCD (drawing a line with a marker on the ribbon helps you remember how deep it was plugged in before). Plugged in the HV power lead and tested the power up to confirm the new display actually works (the first time, there were a bunch of alternating shadows, indicating I hadn’t seated the ribbon connector properly.)
4 screws back in to hold the LCD, 6+1 screws to re-mount the connector board, 6 more to remount the CPU box (and re-connect the ground wires, and 2 of them hold the box shut), then you can shut the case and replace all of those other screws you took out that hold the case together.
Nothing particularly technical – mostly a bunch of screws and tape. And about an hour and an eBay purchase later, the keyboard is back up and running fine.