I recently fixed a problem on a friend's TD-20 display. Here the procedure. Of course, no guarantees that it will fix your problem too, and do it at your own risk. 
- issue fixed: Part of the display faint.
- tools required: philips screwdriver. Optional: small tweezers in case you "lost" a screw in the TD20; a compact flash card to backup data before the operation.
- time required: around 1 hour if you have reasonable mechanical skills.
- convention: for the description consider "top" the side with the display, controls etc...; the back is where you put the cable; front and bottom area as consequence
- How to:
- (optional: backup your data)
- prepare a soft flat surface (e.g. a drape or a towel on a table) to avoi scratching the front ofthe unit.
- disconnect power and all the cables.
- remove the screws on the frontal side (to the side of the compact flash door and on the border) and underneath the unit (except the 4 screws fixing the stand support, if you have it).
- remove the bottom cover and place the unit upside-down.
- you can then access the "main board", be careful! you can identify the backup battery (near the front) and few "flat" cables near the back and lateral borders. If you backupped your data you may remove the battery for increase safety, othewise be careful. Always touch the metallic chassis before handling the bords (this will discharge static energy from your body), "never" touch with metallic objects or your fingers the components and the wires embedded within the board.
- disconnect the flat cables form the board (you remove these cables by gently pulling them perpendicular from the board). Disconnect the small white connector on the back by gently pulling.
- Unscrew the main board (should be 6 screws if I remember), and remove it gently, possibly keeping it form the border without touching the electronic components.
- remove all the screws on the back (near the connectors).
- remove all the boards inside except the last one (keys and control)
- unscrew the drums board (the board where the connectors for the drums are mounted on) and remove it.
- remove the board you find under that (it should be loosen when you removed the screws on the back)
- unscrew the power unit (is encased in a transparent plastic box), pull it on but do NOT remove completely as a short cable keep it connected to the shassis.
- identify the display and its board: the display is a white pastic stuff, witth a small board attached to it. A couple of very small flat cable are coming from the board, and a plastic/aluminion foil covers is on the back side.
- unscrew and remove the display/display assembly.
- being very very careful handling the board, disconnect the small flat cables. To disconnect these flat cables, you do NOT just pull, you must first loosen the lock (gently slide the dark part of the connecto from the white base, the lock is NOT to be removed, just "opened" around 1 mm [1/16"], until it comes to a stop. Do not force! See http://pc-level.com/2011/10/what-is-zif-connector/ or search the web in case of doubt). Once the lock is open the cables are almost loose, you should be able to disconnect them pulling with very small force. Disconnect the flat cable, then reinsert it. This is the actual operation that "fixes" the display by removing subtle oxidation from the cable/connector. If possible do not touch the part of the cable that connects the connector to avoid depositing dirt.
- reconnect the display cable (insert the cable in the connector, then push back the lock gently). Double check to ensure the cables are "straight", otherwise disconnect-reconnect straight.
- reinstall all the boards, screwing at least half of the screws on the back. Make sure you reconnect everything (all flat cables and the small white conenctor near the power module). To reconnect a flat cable, insert it in the connector and push it in.
- Ensure there are not loose boards or screws inside. Reinstall the battery if you remove it. Close the bottom panel (with at least a couple of screws).
- reconnect the unit (drums and power) and test it. Hopefully the display now woks andeverything else too.
- if the display improved but not enough you can try repeating the operation. You can optionally try cleaning the cable using alcohol and a clean fabric, do you at your risk.
- if something (drums, frontal control, output) does not work, re-open the unit and check (disconnect, reconnect) all the flat cables connections on the main board.
When you are satisfied, finish reinserting all the screws.
If it works it will save you 180$ for a replacement display
Enjoy,
Loris.
- issue fixed: Part of the display faint.
- tools required: philips screwdriver. Optional: small tweezers in case you "lost" a screw in the TD20; a compact flash card to backup data before the operation.
- time required: around 1 hour if you have reasonable mechanical skills.
- convention: for the description consider "top" the side with the display, controls etc...; the back is where you put the cable; front and bottom area as consequence
- How to:
- (optional: backup your data)
- prepare a soft flat surface (e.g. a drape or a towel on a table) to avoi scratching the front ofthe unit.
- disconnect power and all the cables.
- remove the screws on the frontal side (to the side of the compact flash door and on the border) and underneath the unit (except the 4 screws fixing the stand support, if you have it).
- remove the bottom cover and place the unit upside-down.
- you can then access the "main board", be careful! you can identify the backup battery (near the front) and few "flat" cables near the back and lateral borders. If you backupped your data you may remove the battery for increase safety, othewise be careful. Always touch the metallic chassis before handling the bords (this will discharge static energy from your body), "never" touch with metallic objects or your fingers the components and the wires embedded within the board.
- disconnect the flat cables form the board (you remove these cables by gently pulling them perpendicular from the board). Disconnect the small white connector on the back by gently pulling.
- Unscrew the main board (should be 6 screws if I remember), and remove it gently, possibly keeping it form the border without touching the electronic components.
- remove all the screws on the back (near the connectors).
- remove all the boards inside except the last one (keys and control)
- unscrew the drums board (the board where the connectors for the drums are mounted on) and remove it.
- remove the board you find under that (it should be loosen when you removed the screws on the back)
- unscrew the power unit (is encased in a transparent plastic box), pull it on but do NOT remove completely as a short cable keep it connected to the shassis.
- identify the display and its board: the display is a white pastic stuff, witth a small board attached to it. A couple of very small flat cable are coming from the board, and a plastic/aluminion foil covers is on the back side.
- unscrew and remove the display/display assembly.
- being very very careful handling the board, disconnect the small flat cables. To disconnect these flat cables, you do NOT just pull, you must first loosen the lock (gently slide the dark part of the connecto from the white base, the lock is NOT to be removed, just "opened" around 1 mm [1/16"], until it comes to a stop. Do not force! See http://pc-level.com/2011/10/what-is-zif-connector/ or search the web in case of doubt). Once the lock is open the cables are almost loose, you should be able to disconnect them pulling with very small force. Disconnect the flat cable, then reinsert it. This is the actual operation that "fixes" the display by removing subtle oxidation from the cable/connector. If possible do not touch the part of the cable that connects the connector to avoid depositing dirt.
- reconnect the display cable (insert the cable in the connector, then push back the lock gently). Double check to ensure the cables are "straight", otherwise disconnect-reconnect straight.
- reinstall all the boards, screwing at least half of the screws on the back. Make sure you reconnect everything (all flat cables and the small white conenctor near the power module). To reconnect a flat cable, insert it in the connector and push it in.
- Ensure there are not loose boards or screws inside. Reinstall the battery if you remove it. Close the bottom panel (with at least a couple of screws).
- reconnect the unit (drums and power) and test it. Hopefully the display now woks andeverything else too.
- if the display improved but not enough you can try repeating the operation. You can optionally try cleaning the cable using alcohol and a clean fabric, do you at your risk.
- if something (drums, frontal control, output) does not work, re-open the unit and check (disconnect, reconnect) all the flat cables connections on the main board.
When you are satisfied, finish reinserting all the screws.
If it works it will save you 180$ for a replacement display
Enjoy,
Loris.
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