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

[Mark Sims]

Hello Karl,

When I tested my quiet 12V fans in the 5370As,  I placed 6 thermocouples around the guts of the machine.  I made a point of sticking a couple of them on heatsinked chips.   The new fan made no significant difference in the readings on any of the thermocouples.  All the readings were within +/- 3 degrees C.

During  the time period when the 5370's were produced brushless DC fans were very expensive and 117VAC fans were cheap.  I suspect that HP just used a standard stock 117VAC fan for cost and convenience.  The one that they chose was a real screamer.

The HP16500 logic analyzers used two 12VDC, 700mA fans.  Most likely it was available from at least two sources and quieter fans were not available at the time.   We had a smallish lab with three of them running in it.  When the safety nerd came by with his sound meter... he was not pleased.  With the quiet 200mA fans and a full load of the most power hungry cards the temperatures in the unit were within +/- 5C (some of which was due to ambient temperature differences between morning and afternoon when the new fans were tested).

The HP16702 series logic analyzers are another matter...  when HP introduced a new logic analyzer card for them (I don't remember which one),  they recalled the older machines to retrofit a couple more (even noisier) fans in them.   Needless to say,  I have not attempted to tame any of those beasties,  but I suspect that you could use lower airflow units.  They added a couple more fans (I think it went from 3 to 5) so that the whole width of the card cage was a wall of fans.

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