[time-nuts] Brandywine GPS-4

[Hal Murray]

> The serial connection is not the problem (unfortunately). It seems a
> thermal problem.... When I switch on the unit it takes a couple of
> minutes before the Error-LED starts flashing. Doing a "fast"
> power-cycle  immediately gives an error-warning (the red-LED start
> flashing almost  immediately after switch-on). When I let the unit
> cool down for some  time (say ten minutes) it takes a couple of
> minutes before the error-LED  comes on. 

I don't have any good suggestions.


> To my opninion everything inside gets quite warm... Maybe it is a bad
> capacitor (high ESR).

The crystal is ovenized so I'd expect that area to be warm.

DC-DC bricks get more than warm when running at full power.  But after the 
crystal warms up the load should drop way down.

I took mine apart and was pleased to find a DC-DC brick.  I found the data 
sheet via google.  It says 20 watts and 9-36V (wide range) input.  That was 
nice since I had 24V handy but didn't have 15V.  The data sheet says 81% 
efficiency, slightly lower at low loads.

My unit gets just barely warm as measured by my fingers on the outside of the 
box.  I don't know what it's like inside.

If you don't find anything obviously wrong/hot when poking around, I can take 
the cover off mine and get some reference temperatures.

It might be worthwhile measuring the input voltage/current, both during and 
after the crystal warms up.








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