Replace fan on 53131A counter with quieter version? - Page 1
Forum section: electronics / testgear

author: motocoder
author_rank: Unknown
timestamp: August 10, 2015, 04:39:22 am
content: Those of you who have 53131A or 53132A counters know that the power switch is actually a "soft" switch, and that the internal fan runs regardless of the power state as long as the device is plugged in.My 53131A is quite old, and that had me wondering how long that fan was going to last. And then that led to a thought about maybe replacing it with a quieter version. Sunon makes some very quiet fans in various sizes, one of which would probably work.So that got me to wondering if someone has already done this replacement? Does anyone know what the specs are on this fan? The service manuals don't mention it. If someone knows what size and voltage this fan is, please share.

author: HighVoltage
author_rank: Super Contributor
timestamp: August 10, 2015, 07:12:14 am
content: It has been several years that I replaced the fan in my 53131A and many other Agilent equipment and it makes a huge difference. But I do not recall the size and model, since I did many different replacements and they are all a little different. But it can be done and it kind of easy on the 53131A.

author: LaurentR
author_rank: Frequent Contributor
timestamp: August 10, 2015, 07:31:04 am
content: I don't have experience with this particular Agilent piece, but for the other 2 I have looked at, the best is to pull it open, look at the existing fan reference and find something comparable from one of the quiet PC fan vendors (Noctua, Gelid...).You could also just drop a series resistance to slow the fan down.As far as the fan connector, I found on the Agilent equipment I have that it uses 2-pin fan connectors that are mechanically compatible with PC 3-pin fans (with the yellow tach output). However, the pinout is reversed (black/red). I found it easier to keep the PC 3-pin connector, extract the pins inside the connector and reshuffle them so that they are compatible with the Agilent pinout. This way, you don't have to splice or cut your original fan.Note that out of the 2 pieces I have, one is 5V, the other 12V, with the same connector, so be careful.

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: August 10, 2015, 07:39:25 am
content: Papstis your friend. Don't cost more than overpriced, LED equipped PC fans, yet actually last a very long time (check the datasheets).

author: motocoder
author_rank: Unknown
timestamp: August 10, 2015, 03:54:24 pm
content: It looked like it was a bit involved to get to the fan, and I was hoping to only have to disassemble it once when I replaced it. But sounds like it's better to be sure and check the existing fan before ordering a replacement.Thanks everyone.

author: edpalmer42
author_rank: Super Contributor
timestamp: August 10, 2015, 05:12:35 pm
content: Have you seen Gerry Sweeney's mod to run the fan only when the unit is turned on? Maybe that's an acceptable compromise.

author: motocoder
author_rank: Unknown
timestamp: August 10, 2015, 08:44:23 pm
content: Quote from: edpalmer42 on August 10, 2015, 05:12:35 pmYes, I've seen that video. I actually have a remote (RF controlled) power switch that I can use to shut off power if I need to rather than modifying the counter. But I did an experiment to see how long it took the OCXO in my 53131A to stabilize after a cold start. It was a really long time - I gave up waiting after several hours. So I think I will leave it on.But replacing a fan should be simple.

author: dadler
author_rank: Unknown
timestamp: August 10, 2015, 08:49:44 pm
content: Don't heating cycles affect the long-term stability of the OCXO? I thought that was why it was such a good idea to leave the OCXO powered constantly (in addition to not having to wait for it to stabilize for each use).I leave my 53132A on all the time, although it does use quite a bit of power and the fan is (was) annoying. I have just gotten used to it and rarely consciously notice it now.

author: motocoder
author_rank: Unknown
timestamp: August 10, 2015, 08:57:03 pm
content: Quote from: dadler on August 10, 2015, 08:49:44 pmYes, it is a good idea to leave it on.

author: engiadina
author_rank: Contributor
timestamp: August 10, 2015, 09:29:31 pm
content: I have two of these counters. For both I replaced the fan with a Sunon fan, was way better than any available Papst fan.There do exist two versions of the power supply. The older runs the fan with full speed all the time, the newer one obviously has some sort of fan speed control.

author: motocoder
author_rank: Unknown
timestamp: August 10, 2015, 10:01:49 pm
content: Quote from: engiadina on August 10, 2015, 09:29:31 pmHi engiadina -I believe mine has a speed control, as the noise increases when I actually turn it on. Can you share the part number for the Sunon you used?

author: dadler
author_rank: Unknown
timestamp: August 10, 2015, 11:02:26 pm
content: My 53132A also increases the fan speed when turned on. I believe mine was manufactured in ~2004. Recently purchased as new old stock, still in original Agilent packaging.

author: TooOldForThis
author_rank: Regular Contributor
timestamp: August 11, 2015, 02:12:32 am
content: I replaced the fan in my 53132 with a "Scythe Mini KAZE ULTRA 40mm Silent Mini Fan (SY124020L)" ($6.92 on Amazon)The original fan had seized up. The Scythe fan fit the mounting holes in the counter perfectly and is barely audible. I'm sure it won't last as long as the original, but at 7 bucks I'm willing to replace it again in 5 years.

author: motocoder
author_rank: Unknown
timestamp: August 11, 2015, 02:30:04 am
content: Quote from: TooOldForThis on August 11, 2015, 02:12:32 amPerfect! That should be enough info for me to get the dimensions of the fan - obviously 40x40 mm, WxH, and I should be able to look up the depth on the Scythe website.Thanks!

author: engiadina
author_rank: Contributor
timestamp: August 11, 2015, 09:35:33 am
content: I found my old bills :-))The fan is made by Sunon, Typ MB40201V3-0000-A99, this type is made for industrial use, has magnetic supported bearings and according to the datasheet the very same parameters as the old noisy fan.I think I paid about 8,- Euro per fan.

author: dom0
author_rank: Super Contributor
timestamp: August 11, 2015, 10:23:12 am
content: Papst standard axial fans are actually not bad - they are definitely not silent, but on the other hand they last for decades and won't get louder with time.

author: motocoder
author_rank: Unknown
timestamp: August 11, 2015, 03:30:30 pm
content: Quote from: engiadina on August 11, 2015, 09:35:33 amOk, for those that want to order something comparable, specs on that fan are: 40x40x20mm, 12VDC, 6.3 CFM

author: HighVoltage
author_rank: Super Contributor
timestamp: August 11, 2015, 04:31:27 pm
content: Quote from: dom0 on August 11, 2015, 10:23:12 amThere are some Papst fans with low noise of only 29 dB(A) and I do think that I used one of those in the counter. But on some Agilent gear that I could not find a fitting low noise fan for, I just added a resistor in line and slowed the fan down and that helped a lot!

author: motocoder
author_rank: Unknown
timestamp: August 11, 2015, 08:31:20 pm
content: I ordered this fan:http://www.digikey.com/product-detail/en/0/259-1633-NDSunon MB40201V3-000U-G9912 VDC6.3 CFM18 dBA3-wire - if the 53131A doesn't need the speed sense wire, I'll just clip it.

author: G0HZU
author_rank: Super Contributor
timestamp: August 11, 2015, 09:25:17 pm
content: I really, really don't understand the reasoning here...You are concerned about the life of a standard Agilent (noisy) fan because you want to leave your counter running all the time. So the solution is to put a low CFPM (silent) fan on the back?I'm not familiar with the inner workings of this counter but I assume it uses a powerful digital vernier system to achieve its resolution. So the counter probably needs a decent fan to keep this high speed digital stuff running cool and to also maintain a reasonably stable inner temperature around the OCXO once the counter is fully switched on and generating internal heat.So in the summer you may find the fan is happy but you may be compromising the MTBF of the expensive parts inside the counter as well as subjecting the OCXO to higher thermal gradients as the counter is switched on and used. This could degrade the frequency stability.Can't you just turn it off when not in use like nearly every other user does? The OCXO should warm up in about half an hour to about 1e-9 if it has had a recent calibration. Maybe 1e-8 if it hasn't. If this isn't quick enough then buy a fast warmup OCXO to use as an external reference.

author: engiadina
author_rank: Contributor
timestamp: August 11, 2015, 09:48:39 pm
content: QuoteObviously.The fan is only effective on the Power Supply. The OXCO itself is covered to avoid any airflow around.Actually those devices are no black box and there is no black magic involved. If you know what you are doing it is a good idea to lower the noise floor as much as possible. Even when I use the counter for long lab days I am happy not to have my ears blown up.I also changed and modified the fan in the 3458A Multimeter because it was way to loud for me and that device is really running all day. So ... it passes all calibrations, nothing's wrong.Why not take care for my ears?

author: G0HZU
author_rank: Super Contributor
timestamp: August 11, 2015, 10:05:54 pm
content: QuoteTaken from Agilent's manual for this counterQuote

author: G0HZU
author_rank: Super Contributor
timestamp: August 11, 2015, 10:14:23 pm
content: Like I said, I'm not familiar with the inner workings of this counter in a technical sense but you can't escape the basic physics of the 30W power consumption.Any heat source adjacent to the OCXO will raise the ambient temperature around the OCXO. This heat source can be the PSU or the high speed digital logic inside the box when it gets turned on.I assume the effect of any unwelcome thermal gradients will be more noticeable with the cheaper timebase options but I think the fan will help move air through/around the unit and keep the internal temperature as stable as possible.The user manual seems to suggest that this is the case as quoted in my previous post

author: motocoder
author_rank: Unknown
timestamp: August 11, 2015, 10:21:40 pm
content: Quote from: G0HZU on August 11, 2015, 09:25:17 pmThe power switch is a soft switch. Turning it off turns off the display, but the fan continues to run. Pulling the plug is annoying and powers down the OCXO, which should be left on.

author: engiadina
author_rank: Contributor
timestamp: August 11, 2015, 10:56:33 pm
content: QuoteI only can tell from my experience. When I had one counter running without case for a while you could even see the effect of just blowing against the OCXO. So I decided to run my own experiments and packed the OCXO into some thick foam. That stabilized the counter noticeable.So when the Power Supply gets warm, why to distribute that into the case? The OCXO is heated anyway. I think gradients are less problematic than changes in temperature.And at least, the new fan has identical parameters compared to the old one, except the noise.The sentence in the manual would not worry me too much. Sometimes manuals contain stuff because of "... oh, we screwed that part. Let's state in the manual, it's serving a special purpose so users don't complain ..."

author: motocoder
author_rank: Unknown
timestamp: August 12, 2015, 02:16:17 am
content: engiadina -I forgot to say thanks earlier. I appreciate you taking the time to look up the fan model number.Thanks,matt

author: G0HZU
author_rank: Super Contributor
timestamp: August 12, 2015, 03:32:55 pm
content: Quote from: engiadina on August 11, 2015, 10:56:33 pmI don't own one of these counters but looking at the images of the chassis on google the vent hole patterns in the case suggest that a fan system would pull in cool air up through the unit so it should vent the warmed air out of the back. But that's just a guess based on how I would expect Agilent to do it.So maybe your fan is fitted backwards?

author: engiadina
author_rank: Contributor
timestamp: August 12, 2015, 10:40:12 pm
content: No, my fan is in the right direction. But you made a good point. Of course the fan is sucking hot air out of the device.Anyway, when you see how the OCXO is mounted, sideways at the frame, directly behind the front panel, I do not know how much the little fan really influences that.but if the replacememt fan has the same params, why bother. Should make no difference but less noise.

author: G0HZU
author_rank: Super Contributor
timestamp: August 12, 2015, 11:13:24 pm
content: Can we now agree that the fan isn't just there for the PSU? If not then read below:Agilent say the fan helps with timebase stability and this makes sense when you look at the 30W power consumption. That's a lot of heat to get out of the box if you want to maintain a steady internal temperature when you leave standby mode.Also the (minimal) vent hole pattern indicates a system that requires a fan to suck cool air through the whole counter. Look at the vents in the enclosure. There aren't many exit vents apart from the entry vents underneath (where the fan draws in cool air). Without the fan the enclosure would get hotter once there was 30W of active high speed silicon.It isn't a case of the OCXO being directly in line with the airflow. It's the fact that the fan unit has to suck the waste heat energy out of the enclosure to minimise the overall internal temperature from slowly rising over time after the counter goes from standby to normal operation. An overall change in internal temperature will not be a good thing for timebase stability.By contrast, I have a slightly older counter from Anritsu that is also a high performance reciprocal/vernier counter and it consumes about 22-24W in normal mode and maybe 4W in standby. So it isn't much different but it doesn't have a fan but instead it has a LOT of holes in the flat top of the top cover and in the underside and the flanks to try and get this unwanted heat vertically out of the box because hot air rises vertically. It has a specific pattern of holes in various places to try and govern the airflow up through the unit.The 53131A has no holes in the flat top of the top cover and so it needs the fan to suck this heat out of the unit sideways via a defined route from the cool air intake on the underside and out through the fan. Otherwise the OCXO/timebase would be in a box that slowly got hotter and hotter once you took it out of standby.Without the fan, I think there aren't enough vent holes (in the right places) to get this heat out of the box without having an undesirable rise in internal temperature.

author: motocoder
author_rank: Unknown
timestamp: August 14, 2015, 12:57:32 am
content: The fan on my 53131A pulls air through the case and blows it out the back.I used the Sunon whose part number I posted earlier. It is nearly silent - definitely quieter than the PCs in the room, and no longer making those "I am going to fail soon" noises.Based on the permanent marker marks and flux residue on the PCB, it looks like this fan was already replaced once. What was installed is a Delta DFB0412M, 12V 0.08A. This is a little higher CFM than what I replaced it with, but based on the comments from engiadina, I think it's comparable to the OEM model.

author: billy_gr
author_rank: Newbie
timestamp: January 24, 2021, 09:12:48 am
content: For reference (and providing some hits for google) replaced a FONSAN DFB0412M with a MF40201V2-1000U-A99 21dBAThank you !!!