Noisy HP 54622D scope, way too much fan noise. - Page 1
Forum section: electronics / testgear

author: PlaneSailing
author_rank: Contributor
timestamp: March 23, 2022, 06:43:54 pm
content: I have an Agilent 54622D which works great - except for the fan noise, it's too loud, am asking if anyone has advice or hopefully a fix.The fan is a Panasonic FBA08A12U spec'd at 12V 0.36A 47CFM and 38dBA. I have tried mounting the fan on rubber grommets, the smallest I could find at my local ACE hardware. Drilled out the fan mounting holes to the 1/4" grommet groove diameter, cut the grommet in 1/2 as it was not deep enough, and did not overtighten the 3 mounting screws. Please see picture for detail - top mounting screw removed for clarity. This had no effect on the noise (I have a sound meter), and don't think the fan frame is "hitting" the case.Sounds like I need a replacement quieter fan - any suggestions ?, thanks.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 23, 2022, 07:05:02 pm
content: And, is it not just bearing noise -- needs at least a cleaning, preferably replacement?I don't recall those scopes being particularly noisy, though it's been a while since I used one.Better way to work with the fan, probably: take it out and power with a bench supply or whatever. Hold it against the table, does it vibrate significantly (table as a sound board)? Does it change if you press on the rotor (watch your fingers!!), or move it around or whatever? Is it buzzing at the rotational rate, or a harmonic (blade noise), or more generalized (white noise, the rushing of turbulent air)?Replacements are easy, anyways; even if it's not a standard size, it's probably awfully close to one. Check drawings for bolt holes. Probably safe to use somewhat less CFM, or higher (say 30+?), I don't know that those things got all that hot inside? Otherwise, equal or greater to be sure about it. And just being ventilation, output pressure shouldn't be a concern. Can opt for ball bearings (or air or magnetic as the case may be?) for long life, and datasheets/supplier catalogs usually list acoustic noise even, so you can sort by that. Blade noise depends on shape, so there's some room to control that while keeping CFM up, but generally speaking higher CFM will of course be noisier, so you can't be too picky at some point.Tim

author: PlaneSailing
author_rank: Contributor
timestamp: March 25, 2022, 01:56:00 pm
content: Thanks for the advice, I took the existing Panasonic fan out, ran it off 12V on the bench, and it's just "white" noise.Thinking the Noctua NF-R8 redux-1800 would be a good replacement ($10 at Amazon in the US March 2022), but it's 31CFM air flow is lower than the original Panasonic's 47CFM, which has me a little anxious. Possibly the original Panasonic was just 20 years ago HP "over engineering" (which is generally a great idea) ?.Be interested if anyone has swapped out the fan in an HP / Agilent scope or logic analyzer, thanks.

author: sorenkir
author_rank: Regular Contributor
timestamp: March 25, 2022, 02:34:59 pm
content: Hi,I have replaced my Panasonic fan with a used PAPST 8412NGML a few years ago.The air flow is lower, but the noise also !I haven't had any problem so far.Michel.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 25, 2022, 04:18:09 pm
content: The most direct consequence of less airflow is likely higher part temperatures, so, a lower maximum ambient before those parts reach their absolute limits in turn. Basically, as long as your lab is habitable it's probably not going to matter.Tim

author: tunk
author_rank: Super Contributor
timestamp: March 25, 2022, 04:28:51 pm
content: From the datasheet:Ambient Temperature: Operating -10 °C to +55 °C; Non-operating -51 °C to +71 °CIf your room temp is below 40, then you probably will be fine with 31CFM.

author: PlaneSailing
author_rank: Contributor
timestamp: April 07, 2022, 10:59:37 am
content: Update on replacing Agilent/HP scope fan.I replaced the OEM Panasonic FBA08A12U 80mm 47CFM (Cubic Feet per Minute) 38dBA (38dB A weighted) fan with a Noctua NF-8R redux-1800 31CFM 17dBA, $10 from Amazon, though unfortunately made in China. The Noctua needed a slight filing of it's plastic case to fit the Agilent metal work. I did not use rubber mounting grommets as found previously they did not help. The 3 way fan plug connected OK with the 2 way PCB connector, not using the yellow feedback connection. With my sound meter I measured an 8dB noise reduction, less than the spec predicted 21dB. The rule of thumb is 1dB is just noticeable, the measured 8dB is very noticeable.The HP54622D is spec'd to work up to ambient 55 degC, 30 degC hotter than my lab, so am comfortable with the reduced air flow.My scope is located close to a wall, so am really liking the the noise reduction, project is recommended.

author: dazz1
author_rank: Frequent Contributor
timestamp: September 18, 2023, 10:35:51 am
content: HiI also replaced my factory fan with a Noctua.It has been a success.The write-up is here:https://www.eevblog.com/forum/testgear/agilent-54600-series-quiet-fan-replacement/