Mark
Thanks for your comments. I suspect that there was a period when the "Papst"
fan was the de facto standard in many equipments, it has considerable depth
and obviously moves a lot of air. I can certainly see the need in the case
of Power Supplies, I have an HP6632A which can provide 100 watts of power.
But a good example of overkill was the HP 3456A Digital Voltmeter, the
earlier models were fitted with a fan, which was subsequently removed in
later issues. I have an older model and I have disconnected the fan (it was
a small type), it was obviously not needed.
I have an HP 5334A, and a HP5335A, the latter being more obtrusive. Perhaps
the design considerations were based on the US, with its higher summer
temperatures,not such a problem for us Europeans.
Roy
----- Original Message -----
From: "Mark Sims" <hol...@hotmail.com>
To: <time-nuts@febo.com>
Sent: Wednesday, May 20, 2009 4:53 PM
Subject: [time-nuts] 5070B once more.... (actually 5370A fans)
Yes, I have replaced the fans in four 5370A and 5370B counters with modern
12V brushless DC motor units connected to the 10V supply. VERY nice and
quiet. I did before and after thermocouple tests in the chassis. The
temperatures were basically unchanged (+/- 3C). Variances could easily have
been due to the probes shifting.
I have also done several dozen HP16500 logic analyzers and Tektronix TM5003
and TM5006 mainfarmes. On the TM5003 and TM5006, I run the fan on 8V. They
are almost dead silent.
Use the lowest current fan that you can find... they tend to be the
quietest.
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