Replacing PS/2 Fans
NOTE: Apologies for the file name, but "/" is not a good character in a file name, and there are many game-toy enthusiasts out there.
9RA0912F40011 SANYO DENKI 92mm match for Model 90 PSU fan
Acoustics - Room acoustics and acoustic properties, decibel A, B and C, Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity and sound attenuation. From The Engineering Toolbox [26 Jan 2023]
Sound Intensity, Power and Pressure Levels - Introduction to decibel, sound power, intensity and pressure.
NOTE: There may be better explanations out there, but instead of spending days searching and learning all the varied aspects, I'm going with The Engineering Toolbox's content. [LFO]
In my decades of tinkering with Personal System/2 computers, it became VERY obvious that IBM used fans that [for the time] were fairly quiet. That is, UNLESS you used a Model 95 as a desk-side system. In which case you noticed the enthusiastic roar of the fan.
Another puzzler, what of the two fan Model 90? What of the fan in a P70? 9556? Or other systems with a "dated" PSU design with components that were under-rated, but were "special-mojo", and those parts are unobtanium.
What we've done over the years is identifying the fan models used in a particular system. Even though the original fan might not be produced anymore, we have the specs.
Static pressure
1 mm H2O=0.0394 inch H2O1 mm H2O=9.8 Pa (Pascal)
1 inch H2O=25.4 mm H2O
1 Pa=0.102 mm H2O
1 inch H2O=249 Pa
Airflow
1 m3/min=35.31 ft3/min (CFM)1 CFM=0.0283 m3/min
1 m3/min=16.67 ℓ/s
1 CFM=0.472 ℓ /s
1 ℓ /s=0.06 m3/min
Sizes
Comparison of Ribbed and Ribless Frames Artwork from Sanyo Denki
Use a ribbed fan in case when clamping through both sides of frame.
Triumph of Engrish.
FALSCH! A through-screw used with a ribless frame.
RICHTIG! A short screw is fastened inside the frame.
Installation Artwork from Sanyo Denki
Fans have symbols on the fan indicating the airflow direction and blade rotation
direction. When installing, use these symbols to check the airflow direction.
NOTE: Pretty much all PS/2s use negative pressure with a PSU mounted fan discharging heated air from the system. Overpressure [Postive ventilation] tends to have dead spots in complex configurations [multiple card, large case, usw...].
The only systems that have overpressure [positive ventilation] are the Gearbox Industrial systems [maybe all Industrial systems?] where you can turn the fans over to change the ventilation direction. Overpressure brings the air through the filters if being used in an environment with high levels of particulates or various gasses.
The Model 90 and 95 are the only multi-fan PS/2 systems that I am aware of. The Model 90 has one fan blowing on the adapters and complex [overpressure?], and another fan in the PSU [negative pressure].
The Model 50 is the only PS/2 I am awae of with a case mounted fan that is NOT integrated into the PSU. Still a negative pressure configuration.
Decibels - Reducing Sound Power and Adding Fan Decibels
Signals - Adding Decibels from The Engineering Toolbox [26 Jan 2023]
The sound pressure level is halved with 6 dB (20 log (2)) reduction.
NOTE: If you wandt the formulas, please go to the linked section. [LFO]
Adding Two Signal Sources with Different Levels
| Signal Level Difference between two Sources (dB) |
Decibels to Add to the Highest Signal Level (dB) |
|---|---|
| 0 | 3 |
| 1 | 2.5 |
| 2 | 2 |
| 3 | 2 |
| 4 | 1.5 |
| 5 | 1 |
| 6 | 1 |
| 7 | 1 |
| 8 | 0.5 |
| 9 | 0.5 |
| 10 | 0.5 |
| > 10 | 0 |
Notice that with >10 dB of difference that the quieter fan adds ZERO dB !
Panaflo Model Designation Code
You probably won't find a fan with every position used. Also, the fans in your PS/2 is 25+ years old. Models have changed over the years.
Example: FBK-09A12M [Model 90 PSU fan]
FB - Panaflo
K - Ball Bearing
09 - 92mm Housing [frame]
A - Housing Thickness
12 - 12 volt
M - Speed [2450 from datasheet]
There are no further codes on the fan, but use your common sense.
FBK-09A12M specs:
NOTE: This was based on a single page from a period catalog. Took HOURS to find.
1.13W
41 CFM [1.16m3/min, 69.6m3/hr]
3.3mm H2O [0.13 inch]
31 dB-A