Replace fan on 53131A counter with quieter version?

[motocoder]

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.

[HighVoltage]

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.

[LaurentR]

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.

[ElectroIrradiator]

Papst is your friend. Don't cost more than overpriced, LED equipped PC fans, yet actually last a very long time (check the datasheets).

[motocoder]

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.

[edpalmer42]

Have you seen Gerry Sweeney's mod to run the fan only when the unit is turned on?  Maybe that's an acceptable compromise.

[motocoder]

Have you seen Gerry Sweeney's mod to run the fan only when the unit is turned on?  Maybe that's an acceptable compromise.

Yes, 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.

[dadler]

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.

[motocoder]

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.

Yes, it is a good idea to leave it on.

[engiadina]

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.

[motocoder]

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.

Hi 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?

[dadler]

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.

[TooOldForThis]

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.

[motocoder]

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.

Perfect! 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!

[engiadina]

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.

[dom0]

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.

[motocoder]

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.

Ok, for those that want to order something comparable, specs on that fan are: 40x40x20mm, 12VDC, 6.3 CFM

[HighVoltage]

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.

There 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!

[motocoder]

I ordered this fan:

http://www.digikey.com/product-detail/en/0/259-1633-ND

Sunon MB40201V3-000U-G99
12 VDC
6.3 CFM
18 dBA
3-wire - if the 53131A doesn't need the speed sense wire, I'll just clip it.

[G0HZU]

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.

[engiadina]

I'm not familiar with the inner workings of this counter

Obviously.

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?

[G0HZU]

Obviously.

The fan is only effective on the Power Supply. The OXCO itself is covered to avoid any airflow around.

Taken from Agilent's manual for this counter

It is normal operation for the fan in the Counter to continue to run after the Counter is
placed in Standby mode. Power to the timebase is continuous to maintain long term
measurement reliability, and the fan helps maintain timebase temperature stability

[G0HZU]

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


 

[motocoder]

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.

The 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.

[engiadina]

I assume the effect of any unwelcome thermal gradients will be more noticeable with the cheaper timebase options

I 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 ..."