[time-nuts] Trimble Thunderbolt 10MHz amplitude jitter

Arthur Dent golgarfrincham at yahoo.com
Mon Apr 19 17:59:10 EDT 2010

Chris Smith-
 "I only joined this list a few hours ago and hadn't searched the archive for
which I apologise."
 No need to apologize. I didn't intend my post to sound like that. this list has
lots of good information but it isn't that easy to find it even if you have been here
for some time.

 The DS1620 8-pin surface mount chip is in the corner of the PC board next to
the RS232 connector and is pretty easy to replace. The strange temperature
you're seeing looks like the same type of failure I saw and is caused by the
DS1620 chip and nothing else. Which revision chip is in there now isn't that
important but if you're going to replace it the way to go is to not use the "E"
revision chip. On the chip there will be 3 or 4 rows of characters. One will be 
DS1620 and one will have a 6 character string consisting of a 4 digit date code 
(for year and maybe week) followed by a "D" or "E" then one more digit. If you 
want the graphic display on Lady Heather to display a smooth non-stepped 
temperature curve, make sure the replacement chip doesn't have an "E" for 
the 5th character in the string. I have replaced a few of the "E" chips with "C" 
chips with a 97 date code and will work fine as do the "D" chips that apparently 
were used by Trimble from 2001 to mid 2004.  I don't know that the "E" chip 
causes any internal problems, probably just the display on the external monitor 
program. Checking the date code on the outside of your Thunderbolt should 
indicate which DS1620 chip you currently have.



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