[time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

Robert LaJeunesse lajeunesse at mail.com
Fri Mar 25 15:52:35 EDT 2016


Personally I'd take a few minutes to look closer at the '232 chip with the scope. Are the charge pump caps swinging 5V p-p and 10V p-p? if not swinging at all, trash the chip. Is -V pin voltage about equal to the negative of the +V pin? If so, that's OK. If not might have an output shorted, or a bad chip. Is the +V pin about +10V?  If so, that's OK. If not might have an output shorted, or a bad chip. With no RS232 driving source connected does the receiver output look like a valid 5V logic high level? If not, look for a short on this line. If all these pass and the chip gets hot, replace the chip.   

Bob LaJeunesse


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