I you mean the sustain type pedals, FIRST check the connector(s) as they often come loose or unseated. Next check for a broken pin in the connectors. It is UNLIKELY you could troubleshoot anything inside with just a meter. It appears that some of the Roland pedals receive 5 volts in the connector, and upon contact closure the voltage is sent back to the piano where it drives C4570 buffers with 680K to ground and an RF bypass cap and series 330 ohm to the + of the C4570's. The circuit I have is for a different piano but if yours uses the 8 pin connector it is likely the same.
The contact is actually optical interrupter modules with a driver transistor. There are threshold setting pots in the pedal assembly as well. The farthest I would suggest you go is to make sure the optical interrupter modules are free of dust if this is the type you have,.
Well, don't jump to conclusions as that particular pedal connection is different than the one I looked up for a different piano. Roland commonly uses NORMALLY CLOSED contacts for this type of pedal...AND the jack they plug into has shorting contacts that default the connections to a short when plug is removed. First thing is to check IF moving the pedal does change the continuity of the connections at the plug when it is unplugged from the piano. They should open when pedals are pushed RELATIVE to the SLEEVE of the TRS (tip-ring-sleeve) connector. If there is only one pedal than I need to know that, but if there is two for this piano, then one pedal should open up the tip and the other should open the ring connections to the sleeve. The tip connection should be the right-most pedal (sustain).
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Thank you for the quick reply, and its obvious you know your stuff. The pedal used on the hp1500 is connected to the piano by a large stereo jack plug(3 points of connection). All these points on the jack plug are shorted out, all cloced circuit. I removed the pedal cluster to find three connections Red, White and screen. I tested all cores individualy for continuity but all are still closed circuit across all three cores. To me this points to a fault with the connecting cable but cannot be sure as I am unsure what reading to expect from the pedal pcb (which looks fairly basic) The connecting cable is visually in good condition, no nicks in it and is has not been crushed.
Thanks again Andy...
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