Thread Starter

alexbez

Joined Jun 3, 2023
5
Hey guys, I am trying to diagnose what the issue is with my Kurzweil CUP2 digital Piano

The piano displays no sign of life besides a red on led.
  • LCD screen does not display anything
  • Buttons do not seem to do anything(there is a little red light above each button that indicates the "mode" it is in. Note, the button above the light should correspond with a button click. Not in terms of being in series, but in terms of the computer/engine board sending a signal to the light above the clicked button to indicate the mode of the piano)
  • Audio In and Audio out on the rear panel do not work either. Note, the piano should have a audio passthrough feature that allows a external device to play audio through the piano's internal speakers and subwoofers.
  • The USB MIDI passthrough is not recognized at all by windows

Sneaky suspicions
  1. I think this could be due to the engine board not working since the engine board updates the LCD screen and LEDs above each button. Additionally, the Engine board controls the muting and unmuting of the speakers during startup and power down to prevent crackling. I think that the audio in at least is not working due to the fact that the Engine board is not doing anything to unmute the speakers in the first place. If I manually unmute the mute relay, would the piano work, or are the sound profiles and all that also controlled by storage on the engine board?
  2. I want to try and reset the CPU and Engine board/even reload native OS, but the problem is that is all done through the interface of the buttons and LCD which do not power on!!!!

Notable details
  1. The workings consist of four main PCBs as noted below:
1685802725383.png
  1. No fuses are blown
  2. The engine board receives power(10V) however the manual says that it should be 5V???
  3. The LCD and Buttons on the control panel do receive power.
  4. There are two LEDs on the engine board, but do not light up at any point?
  5. All cables have been seated correctly and checked for continuity

I have absolutely no idea what the problem, and cause thereof could be.

All schematics required are mapped out here: https://elektrotanya.com/kurzweil_cup2_sm.pdf/download.html

Any help would really be appreciated :)
 

xox

Joined Sep 8, 2017
838
Well, if the engine board circuit is indeed reading 10V, you could well be dealing with an over-voltage issue. In that case, display hardware or other sensitive components may be damaged.

FWIW, the easiest way to go about diagnosing the problem would be to find a working version of that same model and just do a side-by-side comparison of the I/O traffic.

Barring that, it could be a pretty tough nut to crack without any prior know-how regarding that particular keyboard line. Much of the protocols used across brands are widely variable (not to mention highly proprietary) from one make to another.
 

Thread Starter

alexbez

Joined Jun 3, 2023
5
Well, if the engine board circuit is indeed reading 10V, you could well be dealing with an over-voltage issue. In that case, display hardware or other sensitive components may be damaged.

FWIW, the easiest way to go about diagnosing the problem would be to find a working version of that same model and just do a side-by-side comparison of the I/O traffic.

Barring that, it could be a pretty tough nut to crack without any prior know-how regarding that particular keyboard line. Much of the protocols used across brands are widely variable (not to mention highly proprietary) from one make to another.
Ok, thanks! I have also noticed that the D1 and D2 LEDs connected to the CPU do not light up(i think its the tx and rx?) despite all local voltages(besides the 10V in) such as 5V and 3.3V are working??? Could this mean that the CPU is completely blown, or could it simply be another signal preventing CPU statup?

Thanks in advance!
 
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