[time-nuts] Thunderbolt not seeing satellites

Didier Juges didier at cox.net
Thu Jun 10 23:43:32 UTC 2010

My understanding is that you have the older red box. Manual for the red box
is there:


The power spec is 24V nominal, 18V min to 36V max

Mine has been running off a small open frame linear 24V supply for several

If it does not work at 28V, there must be something wrong with it.
I do not recommend trying a voltage higher than 36V unless you have a couple
Franklins to spare. My opinion is that it would be best to try and
troubleshoot the problem first. A power supply problem should not be too
hard to identify, knowing that internally, the Thunderbolt runs from +5V and
+/- 12V. I do not have the detailed specs on these voltages, but the +12V
drives the oven, so it should be stable, even though the nominal value is
probably not too critical. The -12V only drives the RS-232, so it is
probably not critical at all. The 5V drives a lot of logic and should
probably be within 0.25V or better. I suspect the 5V drives the DAC that
drives the EFC, but there must be another regulator/reference between the 5V
and the DAC reference input. I believe TVB did some voltage sensitivity test
at one point on the Group-buy TBs, but off-hand, I do not remember.

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Mark Sims
Sent: Thursday, June 10, 2010 5:33 PM
To: time-nuts at febo.com
Subject: [time-nuts] Thunderbolt not seeing satellites

I'm not sure of the required power spec,  but 28V may be too low.  These
were meant to run off a telco power bus (nominal 48V).  
I run mine at 40V (from a Tek PS503A mounted in a TM501 mainframe,  unit
connected across the + and - supply terminals,  outputs set to +/- 20V).  It
won't run at 28V.

Input  voltage to the poor performing unit is about 28VDC. 
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