[time-nuts] DC-DC converter

Hal Murray hmurray at megapathdsl.net
Sat Sep 26 19:03:35 UTC 2009

> If you want cheap, use 6 12V to 9V DC-DC converters from old thin
> ethernet cards with the outputs in series! This will give 54V. You
> also get the isolation transformers and 10MHz filters see G4HUP's page
> http://g4hup.com/DA/10MHz%20Distribution%20Issues.pdf 

I don't see how that will work.  They can't provide enough power.

The paper above says the little bricks put out 9V at 200 mA, 1.8W.  6 of them 
will total 11W.

My copy of the Z3801A manual says "< 25 Watts (nominal)".  I'm a bit 
surprised HP didn't mention the startup requirements.

Google found a graph at the bottom of:
It shows a measured 0.85A at 47V during startup.  That's 40W.  It drops to 
35W in a few minutes, then gradually ramps down to 32W over a half hour and 
drops to 20W after an hour.  (The text on the graph is tiny.  I might have 
misread something.)

I don't know what the startup power looks like at the sub-second level.

That extra 15 W probably explains most of the startup troubles that have been 
reported.  I'm using a way-overkill 48V regulated supply and I haven't 
noticed any troubles.

These are my opinions, not necessarily my employer's.  I hate spam.

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