[time-nuts] 5070B once more.... (actually 5370A fans)

[Roy Phillips]

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" <holrum at hotmail.com>
To: <time-nuts at 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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