Bv99821 touchscreen troubleshooting - BOSS AUDIO SYSTEMS Boss Dd-3 Digital Delay Pedal

Turning it on and off and on again initializes the keyboard settings. Page EN10 in the manual make that clear. The manual also has a troubleshooting section in the back. https://support.casio.com/en/manual/manualfile.php?cid=008001061

https://ourpastimes.com/how-to-troubleshoot-a-casio-piano-keyboard-12352821.html

check any data cable loose connection, if other fuctions of the keyboar are working, if other functions not working, main board faulty, get a roland service center

Take it appart rub it with pure alcohol an put the touchpad together again

Where can i purchasea lcd for my korg triton studio

You will have to go to Korg to get the replacement screen.

Here: http://www.guitar-parts.com/catalog/korg/korg-touch-screens-lcds

Wow ... $300... ouch...!!!

You will have to go to Korg parts to get the exact replacement... these are not generic items.

Try this: Korg Parts (Parts is Parts): 1-800-590-0014

Check C131 which should have 5 volts across it. This powers the analog switch chip that has to select the audio channel and routing. If 5 volts isn't there, check cap for a short. There are too many other possibilities to enumerate here. You need electronic test equipment to troubleshoot this problem and some skill at troubleshooting.

Here is your schematic:

http://elektrotanya.com/marshall_mg50dfx_sch.pdf/download.html

The unit may have the problem that befalls the Palm Pilots where something gets under the escutcheon and presses on the touch screen at the edge which overrides any other inputs.

Another possibility is a stuck button. The buttons are usually scanned as a matrix and at startup if a button is stuck that can make unit unresponsive.

Without a logic analyzer and the firmware listing you likely would not get far if one of the logic chips has gone bad unless it can be found using freeze mist and heat gun..

Stuck buttons or touch screen is usually easily found without schematic.

Just a hint to troubleshoot: Connect a 100 Watt light bulb in series with the hot side of the power line into the amp. Make a cord with a light socket and a receptacle to plug the amp into. This acts as a resetable fuse and will send enough current through the amp to not fry stuff, but enough to do troubleshooting.

Here is a troubleshooting hint:

Put an incandescent lamp in series with the hot side of the power cord. This acts as a resetable fuse while troubleshooting so you don't blow fuses.

Schematics are hard to come by, but power supplies are easy to trace the circuitry.

Check filter caps and the diodes and THEN look for hot (temp) IC's and transistors.