Hi,
Has anyone tried replacing the fans of some of the older HP test gear?
They make a lot of noise, can't help thinking there are better - or at least quieter - ones to be found thanks to the PC market.
-- John Devereux
Most of the ones I've taken apart are 120V.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Once an HP fan, always an HP fan. Looking to join an HP fan club?
Hint: I like HP test equipment.
Do you mean very old equipment, or slightly old equipment? The really old fans will run forever. Real bearing, that can be lubed. Brute horsepower that will turn the blades even when buried in muck and packed with dust. Genuine intake filters. I don't recall ever replacing a really old fan. The not so old fans are more "modern" using plastic frames, bushings, DC power, minimal horsepower, and marginal filters. While not as good or reliable, they do make less noise.
What you'll probably find is that a fan that moves the same amount of air in CFM (cubic feet per min), will make about the same amount of noise. The only way you're going to reduce the noise is to use a smaller or slower fan, which I don't recommend. Ear pads are cheaper and easier.
I don't think you will have good results replacing the big fans with a PC style fan. They just don't move enough air (CFM), have problems with the bushings, and clog easily. They also don't do well with the high internal heating found in some of the older HP test equip. Something big by Rotron or other reputable manufacturer will probably work, but I think you'll find it almost as noisy as the original.
Besides, modifying an HP instrument from stock is considered sacrilege.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I am approaching that level of excess, if you include some Tek and Keithley stuff too :)
I guess I must have a mixture, but all pre-agilent stuff.
With computers, IME the fans tend to get quieter as they get bigger (larger diameter). Most of the noise on the HP fans sounds to me more like the motor or bearings. Rather than air movement. A moaning sort of whine, rather than a whooshing.
Oh yes I can see that too!
-- John Devereux
Something like that. Tip vortexes and turbulence create most of the noise. Spin the fan slower, and much less noise. Details:
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
A collegue of mine changed the fan on the E36xx series. Or rather he just a dded a control to shut it off if it was running cold (why they did not add that it the first place I don't know). AFAIC he had to add special circuitr y since it would detect fan failure.
Most HP gear is great, but some are funny like the fan operation. Other spe cial features, like that on the HP33120A function generator it is not possi ble to turn the output off. And that duty cycle is limited from 20 to 80%. Tsk tsk..
Cheers
Klaus
I am sure HP is like any other big company.
When engineering is finished with it and throws is over to manufacturing, things will get changed.
"Oh, this cheaper fan will be fine".
And a fan will not get pushed back to engineering for re-evaluation.
hamilton
. AFAIC he had to add special circuitry since it would detect fan failure.
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