I am fitting one of these into a HP 5335A counter. The project became a bit
more involved than it first seemed and part of that is how to deal with the
cooling. The manual shows an AC fan but it had been replaced (sloppily, I might
add) with a DC fan which was terribly noisy. I found a much smoother one with
even more airflow in my junkbox. The 5680A is mounted near where the fan is so
it gets plenty of airflow, but what about when the unit is in standby? What I
did was put a little relay in which is powered by one of the DC supply outputs.
When the unit is off, the relay opens which places a resistor in series with the
fan (which is now powered by the small laptop 15 volt supply I installed).
Thus, when in standby the fan drops to a lower speed and acceptably quiet
operation and the 5680A doesn't get too hot. I determined the resistor value
experimentally via my super duper accurate
run-unit-for-a-while-remove-cover-feel-5680A-case-change-resistor-repeat
method. Ok so I'm not looking for supreme accuracy of temperature, just good
operation.
Nifty little project to get great accuracy for half the price of a good used HP
oven oscillator.
Peter
On 2/29/2012 6:03 AM, Attila Kinali wrote:
On Tue, 28 Feb 2012 11:42:51 -0800
Chris Albertson<[email protected]> wrote:
It's clear to me from seeing all those screws that
the 5680 needs to be firmly connected to some kind of heat sink even
it only a large plate.
It could also be that those screws are used to hold the top
and bottom part of the cover firmly together. Dont forget that
Rb's are sensitive to magnetic fields and that the case is mostlikely
made of some high permeability material.
Attila Kinali
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