Roland Jd-800 Main Board

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When pulse appears only at pin number 2 of IC9 :

Check R46. IC9. IC10; L6, CN6 Con the JB) and their peripherals. Especially chack that there is no short circuit in the patterns. If there is no bad connection between CN6 (on the JB) and CN15 (on the MB), IC9 (on the JB) may be defective. Since a similar problem is caused when there is a short circuit in the peripheral patterns of CN15. check the same thing with the wirings being disconnected from CN15.

When a pulse appears at pin number 2 and pin number 6 on IC9 :

Check L6 (on the JB). Check also the connection between CN6 (on the JB) and CN15 (on the MB).

When a pulse appears at all the pins :

Check that there are no loose pins or pattern cutoff of IC36 (on the MB). If everything is normal. IC36 may be defective.

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[5] Other Malfunctions

1.Keyboard Malfunctions a) Sound isn't output when keys are pressed. • Make a thorough test of the keyboard, referring to [11] in the TEST MODE section, p.32.

When there are no sounding keys within an octave :

The scan line of the keyboard matrix may be defective. Check that there is pulse waveform at pins numbered 8—16, 63—68. 70—75 and 77—80 on IC11 on the Main Board. Check the cable which connects the Main Board to the keys as well. It is also possible that the flexible plate on the keys is defective.

When sound isn't output from any of the keys :

There is a possibility that the keys are not being read correctly. Check IC11 and its peripherals on the Main Board. Also check the cable connection from the keys to CN7 on the Main Board. The keys themselves may also be defective.

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Observe pin number 26 on IC11 by oscilloscope in order to find out whether keys are read in by IC11 or not. When the keys are not pressed. High level is output, but when a key is pressed, a pulse is output at Low level for a second. This is because_ IC11 reads the keys and as a result it interrupts the CPU. Confirming this makes it almost certain that the keys are being read correctly. If you want to make absolutely sure of this, observe pin number 77 on IC36. All the interruptions from all the ICs on the Main Board are unified by IC13 and are input in pin number 77 of IC36 which is the CPU. In this way many pulses can be observed, so find the pulses which appear only when the keys are hitted.


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