Roland JV-90 keyboard

[maleksa]

I have a Roland JV-90 keyboard.

When I switch it on from cold it works perfectly. However, after a few minutes it starts to act strangely. The LCD screen shows garbage, the LED lights starts to blink randomly and the sound that comes out are intermittent.

I notice that the main IC (Roland R15239229) gets hot (more than 50 degrees C).

What could be the problem?
Why does it go crazy only after the circuit warms up? Could it be due to a blown capacitor, resistor or IC?

Any help/pointers would be of great help.

[CapLeaker]

Re: Roland JV-90 keyboard

Verify that the IC you are thinking about is actually the problem. You can do so by heating the IC with hot air or freezing the IC a with a can of air (duster spray) upside down. You can try to reflow it too and see what happens. But after that chances are high that the IC is faulty.

[stj]

Re: Roland JV-90 keyboard

or the voltage is not properly regulated - i would check the 5v or 3.3v actually is, and is not creeping up as the psu warms up!

[maleksa]

Thanks for all your pointers and feedback.

Just to update everyone, I downloaded the Roland JV-90 service manual which had the schematics. I did the following
1. I measured the XRES voltage at the power board and at all the ICs (that receives the XRES voltages) on the mainboard
2. I measured the 5V at the power board and at all the ICs on the mainboard
3. I also checked the capacitors to ground at all the XRES and 5V above (to check that they are not shorted)

After doing the above, the JV-90 worked perfectly. I also left it on for about 6 hours and there were no problems. I really do not know what happened (perhaps one of the ICs was reset when I took the voltage measurements?) but it is now working perfectly till today.

[kevingill]

Sometimes just testing the board with probes remakes a dry joint and fixes the issue. If it comes back again, check each joint under a scope and reflow the solder.