[time-nuts] Anybody want a Thunderbolt power supply?

Dr. David Kirkby drkirkby at gmail.com
Thu Sep 1 04:07:12 EDT 2016

-------- Original message --------
From: Charles Steinmetz 
Date:09/01/2016 06:07 (GMT+00:00) 
To: time-nuts at febo.com 
Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply? 

Randall wrote:

> Tested and guaranteed samples of all of these can be bought for $25-100 
if you are patient (pay no attention to the loonies who list them for 

The problem on eBay is "tested" means something quite different to what I know as "tested'. 

> There are two potential disadvantages.  The first is size (particularly 
WRT the Power Designs units -- the HPs are much smaller).  The second is 
their adjustability.  You would not want to brush against one of the 
voltage-setting knobs accidentally and send your Tbolt to GPS heaven. 
The cure for this is a small dab of RTV on each knob.  

There are a number of HP power supplies that have over voltage trips.  You. can program them to switch on with an output voltage of V1 and a trip of V2, where V2 > V1. So even if you accidentally turn the knob and increase the voltage, no damage will occur as the PSU voltage drops to zrro. 

The above said, I set up an HP 6674A  option J02 (70 V, 30 A, 2100 W) supply to switch on at 13.8 V. Setting the trip at anything less than 14.1 V (from memory), meant it would trip at startup. If one wanted it to trip at 13.85 V, one would need to set the voltage lower,  then slowly increase to 13.8 V.

I have a number of HP/Agilent PSUs, and they all have over voltage trips. None of the PSUs I have are their "precision" ones.

The units I have do I believe have a local lockout facility which can be programmed by GPIB. 


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