Hello, I'm currently trying to make a DX7-IID work. At power-up, all LEDs and the display lights up, and nothing more happens. Measuring at the MPU, it does get the 8 MHz clock signal, but it does not output the 500 KHz clock signal at pin 15. Besides, most of the adress pins (34-50) have a weird output of constantly 1.5V. - and at a few of the pins above 50, there is a slight trace of the 8 MHz clock signal. I have measured the TC40Hxxx circuits directly connected to the resonator and the crystal; they seem to work ok. And none of them run hot. As a matter of fact, nothing in the machine runs hot. All in all, I'm suspicious that it is the MPU that has given in. Does anybody have any experience with this problem? Frankly, I hope it is something else than the MPU, it seems to be quite a job to desolder it and replace it with a new one. Any ideas will be appreciated! Best regards, Helge
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Yamaha DX7-II refuses working
2011-01-23 by hnrgaardmadsen