Hi all,
I got a Yamaha NP-30 with no sound.
Power LED lights up when pushing the on button, but pressing any key doesn't produce audio on the speakers.
I tried plugging in headphones, but no luck there either.
Voltages seem fine. Input is 12VDC, goes down to 5VDC, then 3.3VDC and 2.5VDC. There's no obvious damage on the PCBs, nor bad caps that I can see.
I've looked at the opamps in IC402, but there's no signal on the output when pressing keys.
So I looked at the output of the DAC, but there's nothing there either.
Then I looked at the input of the DAC and it does look like some data is being written to it from the CPU SDO pin.
The DAC has a master clock (pin 1), which looks like this:
Looks like a sawtooth between 1V and 2V.
But looking at the datasheet it seems like the DAC wants a TTL clock:
So if my scope measurement is right, the clock sent by the main CPU has the wrong voltage.
It's lower than VIH and higher than VIL...
I tried injecting a 3V 11MHz square wave to the master clock with a 3325A, but that didn't do anything.
If anyone here has a Yamaha NP-30, that's willing to measure the master clock so I can be sure mine is f'ed or not that would be neat.
I've attached the schematic, but you can find the full service manual (with PCBs) online.
Any help is appreciated.
PS: I don't know the history of this yamaha keyboard. The guy I got it from said he bought amplifiers and that came with the lot.