Cooling Fans
IMSAI recommends a cooling fan for systems and cabinets with more than a couple of S-100 cards installed.
It is highly recommended that all systems and cabinets with linear power supplies
(those with large electrolytic capacitors in cans), because these systems typically dissipate much more power than
newer systems and cabinets with switching power supplies.
Although the original FM (Fan Module) fan shipped by San Leandro throughout the 1970s is no longer in production, we have located a few stashes and can get a limited quantity of them.
If you absolutely must have the original IMSAI fan, get them while they’re still available!
Ordering
| Description | Part Number | Availability | Unit Price (USD) | Quantity | Ordering |
Fan, AC, 115 V, Original IMSAI model | FM | 6/15/2025 | $69.00 | | |
Fan, AC, 115 V, Generic | FM G | 10 day lead time | $49.00 | | |
| Fan, AC, 115 V, Quiet (55 CFM) | FM Q | 10 day lead time | $49.00 | | |
| Fan, AC, 230 V | FM 230 | 10 day lead time | $49.00 | | |
| Fan, DC, 12 V, 55 CFM | FM 12 | 10 day lead time | $19.00 | | |
| Cabinet Fan Finger Guard, 3-ring Metal (Rev. 1) | 70-90000000 | 10 day lead time | $3.00 | | |
| Cabinet Fan Finger Guard, 6-ring Plastic (Rev. 2) | 70-90000001 | In stock | $3.00 | | |
More Information
Newer IMSAI power supplies, beginning with the PS-28S support standard 120mm PC case fans with up to 4 pins.
PC case fans are available in a variety of designs with varying airflows.
Most of the popular online stores carry PC case fans. Just make sure they are 120mm and draw 6 watts or less.
In systems with a switching power supply, high airflow is typically not needed.
The FM, FM G, FM Q, and FM 230 kits come with the fan, cables, heat-shrink tubing, and instructions.
The FM 12 kits come with the fan with integrated cable and 3 or 4-pin connector and instructions.
Power Supply Compatibility
The following table lists the fan modules and their compatibility with IMSAI power supplies.
Note that some of the fan modules listed may not be currently available.
| Fan Module |
Comments |
Power Supply |
| PS-28 ¹ |
PS-28U |
PS-28S |
| FM |
89 CFM, 115 VAC, 60 Hz. The original IMSAI fan! |
Yes |
Yes |
Yes |
| FM G |
70 to 90 CFM, 115 VAC, 60 Hz. Generic “original” fan. |
Yes |
Yes |
Yes |
| FM Q |
50 to 60 CFM, 115 VAC, 60 Hz. Lower airflow and quieter. |
Yes |
Yes |
Yes |
| FM 230 |
70 to 90 CFM, 230 VAC, 50 Hz |
No |
Yes ² |
Yes |
| FM 12 |
55 CFM |
No |
No |
55 CFM |
| FM 12-LOW |
24 CFM |
No |
No |
24 CFM |
| FM 12-PWM |
PWM, up to 81 CFM |
No |
No |
55 CFM |
| FM 12-TC |
Temperature controlled, up to 56 CFM |
No |
No |
≤ 56 CFM |
¹ Includes PS-28 and all predecessors with 115 VAC power transformers.
² Requires wiring to the PCB switched outlet pads instead of the 115 VAC primary tap.
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