There have been reports from several people that the CPU on some Rajiva MCU Update installations resets spontaneously. I had observed this happening a few of these at the Texas Star Party. The best guess at why this happens is that the RA motor relay is radiating and causing noise on the RST (reset line) on the CPU. This is pin 9 on the chip and as an attempt to filter any noise out I put a 47pF silver-mica capacitor from pin 9 to pin 20 (ground) and a 1K3 pull-up resistor from pin9 to pin 40 (5v).
On the bench the modified MCU performed perfectly over two dozen GoTos with guiding/slewing from the hand controller at the end of each (to simulate centring the star). No resets occurred and the mount functioned as advertised. Whether this has finally fixed the problem or not is still up in the air but so far it works. If you STILL experience the occassional reset try gluing aluminum foil over the relay to shield it.
Here is an image of the MCU board.
Note: The way I put the capacitor in the leads could be bent down and cause a short to another pin on the chip so I stripped some small wire and insulated the legs of the new capacitor by sliding the insulation from the wire over the legs; no more worries. The position of the resistor is not a problem in this way.
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