[time-nuts] Trimble Thunderbolt GPSDO Troubleshooting

Ryan Stasel rstasel at uoregon.edu
Fri Mar 25 21:33:21 UTC 2016


Hi Bob, 

I think I’m going to take a look, since I couldn’t find a spare, so I’ve got a couple on order (and a few days to wait). 

So, looking at the datasheet (http://www.intersil.com/content/dam/Intersil/documents/icl2/icl232.pdf), you’re saying check the two caps across pins 1 and 3, and 4 and 5, and make sure they’re swinging. And also check to see if Pin 6 is at “ground” (basically). +V should be at around 10V? Likewise, I’d assume the input to that stage (wherever it comes from) should be a nice logic level input. 

And then lastly, you’re saying lift/cut pins 10 (and/or 11, depending), and then look at 7 or 14 and see if they’re sitting at 5V (they wouldn’t sit at +10V)? It’s actually kind of funny that they used this chip, since it’s whole point is to eliminate the need for ±12V… except this board specifically has ±12V! =P

Anyway, I’ll check all this as best I can, or just get frustrated lifting pins, and remove the whole darn thing (like Clint suggested). =P 

Thanks all! 

-Ryan Stasel

> On Mar 25, 2016, at 12:52 , Robert LaJeunesse <lajeunesse at mail.com> wrote:
> 
> 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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