Magnus wrote:
Having 1-10 kW per rack is not uncommon these days, so
forced convection needs to be done
That and more. A fully loaded 42U rack of HP C-class blades runs 8 kW idle and
peaks at 24 kW.
This can be air cooled (easily) in a properly designed and commissioned
run-of-the-mill
In message blu125-w32eb9626acf899c8949ffce...@phx.gbl, Mark Sims writes:
Many failed electrolytic caps on PC motherboards and in PC power supplies
can be traced to a case of industrial espionage gone wrong. [...]
While this tale is true, the fact is that even without incompetence,
electrolytics
One comment, and one idea on airflow...
I've noticed that none of my high-end frequency standards use
fans at all. That includes every Rb, Cs, and H-maser. This does
not mean they are all cool to the touch, but my guess is it's better
to allow temperature gradients to exist than use fans in an
Tom Van Baak wrote:
One comment, and one idea on airflow...
I've noticed that none of my high-end frequency standards use
fans at all. That includes every Rb, Cs, and H-maser. This does
not mean they are all cool to the touch, but my guess is it's better
to allow temperature gradients to
At 10:13 AM -0700 5/22/09, Tom Van Baak wrote:
One comment, and one idea on airflow...
I'm sure we could discuss for some time what airflow is too much
or too little or where to place the thermal probes or how to take IR
scans or how then interpret them. But it seems to me the bottom
line is
In message 4267588cdd7544d48a9a119584228...@pc52, Tom Van Baak writes:
I'm sure this requires no small effort in thermal engineering on
their part.
The major part of this effort was to reduce the power usage to
maximize battery lifetime.
The plot you get is then simply accuracy (or jitter or
When I swapped my 5370A AC fans for DC fans I was concerned that the inverter
in the fan motors might have some effect on the performance of the
instrument... after all, it is measuring stuff at the part per trillion level.
I was rather surprised to see that, if anything, the internal
In message blu125-w59049fd49ae9ec2fa1474ce...@phx.gbl, Mark Sims writes:
I was rather surprised to see that, if anything, the internal jitter went
down a couple of picoseconds
That could easily be reduced microphonics in the OCXO because the new
fan does not rattle around as much.
--
rich...@karlquist.com said:
First of all, the 5071A has to be able to run on a battery, so you can
do the flying clock experiment.
Did you have any trouble convincing the airlines and/or FAA that it was safe
to take an atomic clock on a plane?
I'd be more worried about the big batteries than
Hi!
Regarding the comments below on the 5370: there are always two
questions with temperature: meeting spec and reliability. Instruments
vary as to which is a bigger issue. Some have temperature
proof measurement techniques that will work virtually until
something burns up, so you can get
The reason for the fans is to prevent premature failures of the
silicon devices due to thermal degradation. The life of a silicon
chip is halved for every 10C temperature increase, more or less.
I was going to make a similar comment, but got sidetracked poking around
google. I didn't find
Hal Murray skrev:
The reason for the fans is to prevent premature failures of the
silicon devices due to thermal degradation. The life of a silicon
chip is halved for every 10C temperature increase, more or less.
I was going to make a similar comment, but got sidetracked poking around
Hal Murray wrote:
The reason for the fans is to prevent premature failures of the
silicon devices due to thermal degradation. The life of a silicon
chip is halved for every 10C temperature increase, more or less.
I was going to make a similar comment, but got sidetracked poking around
The power dissipated in a modern CPU chip (watts per sq cm) far exceeds that of
a cooking hotplate. There are some videos on YouTube showing CPU's literally
exploding when they loose cooling for just a short time. ECL is a rather
chilly iceberg in comparison...
M. Warner Losh wrote:
In message: 20090522185851.4137db...@ip-64-139-1-69.sjc.megapath.net
Hal Murray hmur...@megapathdsl.net writes:
:
: rich...@karlquist.com said:
: Did you have any trouble convincing the airlines and/or FAA that it was
safe
: to take an atomic clock on a
In message 4a170da2.3080...@rubidium.dyndns.org, Magnus Danielson writes:
Hal Murray skrev:
There are being books written about this. One that I have found being a
fairly short but useful one is the ATT Reliability Manual.
It is worth pointing out that a very large fraction of all electronics
In message 971f24636bd13158d9fe412ec6c9c885.squir...@webmail.sonic.net, Rick
Karlquist writes:
The old photos of Len Cutler watching the airline porters carrying
the clock up the stairs to the plane give the impression that
the airline was honored to be asked to participate.
According to a SAS
Poul-Henning Kamp skrev:
In message 4a170da2.3080...@rubidium.dyndns.org, Magnus Danielson writes:
Hal Murray skrev:
There are being books written about this. One that I have found being a
fairly short but useful one is the ATT Reliability Manual.
It is worth pointing out that a very large
Mark Sims skrev:
The power dissipated in a modern CPU chip (watts per sq cm) far exceeds that of
a cooking hotplate. There are some videos on YouTube showing CPU's literally
exploding when they loose cooling for just a short time. ECL is a rather
chilly iceberg in comparison...
The
Poul-Henning Kamp wrote:
It is worth pointing out that a very large fraction of all electronics
failures are not semiconductors but electrolytic capacitors.
People are often astonished when I tell them, that a long life
electrolytic capacitor is one which will last one year at its rated
Many failed electrolytic caps on PC motherboards and in PC power supplies can
be traced to a case of industrial espionage gone wrong. Somebody sole the
formula for the caps from a Japanese company and sold it to a competitor. That
competitor allegedly cranked out over a billion of the caps
Mark Sims wrote:
I have done quite a bit of work replacing fans in old equipment with modern
fans.
I have never seen a case where replacing a hurricane level fan with a
whisper
quiet fan made any real difference in the cooling inside the unit...
typically
one sees less than +/- 5C
In message 4a15808f.4090...@karlquist.com, Richard (Rick) Karlquist writes:
Modern fans obey the same laws of physics as the original equipment.
They don't magically produce more airflow for less noise.
Agreed: there is no magic to it.
But a lot has happened in aerodynamics since Hermann Papst
-Original Message-
From: time-nuts-boun...@febo.com
[mailto:time-nuts-boun...@febo.com] On Behalf Of Richard
(Rick) Karlquist
Sent: Thursday, May 21, 2009 9:26 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 5070B once more (actually 5370A
pointed out by others.
Didier
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Poul-Henning Kamp
Sent: Thursday, May 21, 2009 12:12 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 5070B once more
This is incorrect. ECL components require a minimum airflow velocity
that is rather high. The purpose of the large fan is to maintain this
velocity. If a smaller fan is used, the ECL components will get
hotter, even though the air flowing past them is not much hotter.
When you say the fan
Hal Murray wrote:
How much ECL is used in a 5070?
A bunch
How tightly are they packed?
You need a high cooling velocity even if just one chip.
How much of
the heat goes directly from the chip to the air rather than from chip to
board to air?
A substantial amount of cooling is from DIP to
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
When I worked in RD at HP's Microwave Division (1972 ~ 1976) and HP LaserJet
Division (1976 ~ 2000) we designed all our products to meet specifications
across a temperature range of -20 to +55 degrees Centigrade. I would assume
this was a standard requirement across most if not all HP products
The ECL and EECL chips are located on A22 (arming board), A19 + A20
(interpolator boards), A18, A17 (count chain assembly) A8 (reference
buffer), A21 (multiplier assembly).
The interpolator boards are more or less directly in line with the
ducted airflow from the fan as are the reference buffer
A8? Reference buffer? Gee, I thought was the electrostatic dust magnet ;-)
That puppy can grow more fuzz than a sheepdog. In all the machines I have
worked on, it was utterly disgusting.
BTW, the best way to locate where to drill the access hole for the oscillator
tuning pot is to look
I came home one day to find *that* smell in my workshop. It turned out to be
my HP 3325B. It had been on for ages and it had also been a warm day. I
looked at the back and found the intake completely blocked up with dust.
It seems to still work, but I need to open it right up and check it out
: [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
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
, 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
When I have been concerned with 'stealing' power, I have used
a switching power supply wall wart. Small and are usually quite
efficient. One model a Sony (branded), the chip inside even had
a opto isolated control pin so it could be turned on/off via
logic.
-pete
Yes, I have replaced the
I have done quite a bit of work replacing fans in old equipment with modern
fans. I have never seen a case where replacing a hurricane level fan with a
whisper quiet fan made any real difference in the cooling inside the unit...
typically one sees less than +/- 5C difference anywhere inside
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