Getting power to a fan on an old computer... is the sound board an option? \ VOGONS

Getting power to a fan on an old computer... is the sound board an option?

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First post, by NightShadowPT

Posted on 2022-10-09, 18:21

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Hi,

As stated on another topic, I have recently acquired a Compaq Deskpro 486/33.

That PC came upgraded with a Cyrix cx486 DX-2 @66Mhz, but there is no fan installed on top of the CPU cooler.

To compensate for it, I was thinking about getting an 80mm fan in the case blowing past the CPU, but I have hit a "slight" snag... I cannot seem to find any place where I can connect the fans at all - there are no 5v pins on the board and all my fans are 5V 80mm Noctua fans - so I cannot just use a Molex to fan adapter.

While thinking about options I noticed that my AWE seems to have an awful amount of pins going out of it... and I had a crazy idea that maybe one of them could be a 5V one I can use.

I guess my questions here are:
1 - Is there a 5v output from the AWE32 that I can use?
2 - If there is, should I use it for this purpose or is it not advisable
3 - Any other suggestions short of buying a 12v fan?

Thanks!

NightShadowPT
----------------
Compaq Deskpro M 486/66 - 64MB Ram - Compaq QVision 1MB - Orpheus II Sound
Card - 4GB SCSI HDD + 4GB CF Card - SCSI CD-ROM Plextor PX-32TSi - Adaptec WideSCSI AHA-2740W - 3COM Etherlink III Card

Reply 1 of 11, by RandomStranger

Posted on 2022-10-09, 18:50

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NightShadowPT wrote on 2022-10-09, 18:21:

there are no 5v pins on the board and all my fans are 5V 80mm Noctua fans - so I cannot just use a Molex to fan adapter.

Why not? The red wire is 5V and there are adapters that use that instead of the 12V or have both.

Reply 2 of 11, by darry

Posted on 2022-10-09, 18:56

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You can use a Molex to fan adapter, you just need switch the wire from the 12V to the 5V pin on the adapter. The Molex connector carries both 12V and 5V.

I would be surprised if pre-wired adapters of that kind did not already exist.

EDIT: @RandomStranger, you beat me to it.

Reply 3 of 11, by weedeewee

Posted on 2022-10-09, 19:13

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something like this could do.

https://www.amazon.co.uk/15cm-Akasa-Fan-Cable … s/dp/B001J2YRU2

716nZM2VDaL.__AC_SX300_SY300_QL70_ML2_.jpg

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Reply 4 of 11, by Doornkaat

Posted on 2022-10-09, 19:14

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There are plenty 4pin molex>3pin fan header adaptors that use the 5V rail. They are really easy to find.
Using the sound card instead may introduce unwanted noise.

Reply 5 of 11, by NightShadowPT

Posted on 2022-10-10, 11:27

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Clearly my bad...

When I searched for Molex to fan adapter I could only find 12v versions, so I just assumed it only had 12v.

Thanks for clarifying that it also carries 5v, it is without any doubt the cleanest solution I can get.

Cheers,

Reply 6 of 11, by weedeewee

Posted on 2022-10-10, 15:11

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FYI, in the photo I posted, two of the connectors are wired for 12v, the other 2 are wired for 5v.

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Reply 7 of 11, by darry

Posted on 2022-10-10, 15:26

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weedeewee wrote on 2022-10-10, 15:11:

FYI, in the photo I posted, two of the connectors are wired for 12v, the other 2 are wired for 5v.

@OP Do not mix them up and preferably test before use that they are wired correctly .

Reply 8 of 11, by kdr

Posted on 2022-10-10, 21:13

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I often re-wire the Molex connectors of 12V fans to run them off the 5V rail instead, this makes them run fairly slow and very quiet. If you have a tiny screwdriver and some patience it's possible to slide the pins out of the plastic housing, so you don't even need to crimp or solder anything!

(Edit: of course the opposite doesn't apply, you can't take a 5V fan and decide to run it on 12V.... unless you want magic smoke!)

Reply 9 of 11, by psychofox

Posted on 2022-10-11, 13:41

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kdr wrote on 2022-10-10, 21:13:

I often re-wire the Molex connectors of 12V fans to run them off the 5V rail instead, this makes them run fairly slow and very quiet. If you have a tiny screwdriver and some patience it's possible to slide the pins out of the plastic housing, so you don't even need to crimp or solder anything!

(Edit: of course the opposite doesn't apply, you can't take a 5V fan and decide to run it on 12V.... unless you want magic smoke!)

Lots of 12v fans wont run on 5V voltage (they run but need extra push at start). So i have wired my fans between 12V and 5V wires (12v line to fan + wire and 5V to - ) the voltage between them is about 7 V, this way fan is silent and still has enough cooling power on most cases.

Reply 10 of 11, by RandomStranger

Posted on 2022-10-11, 19:23

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Noctua used to include resistor modded wires for their fans. They call it low noise adapter and ultra low noise adapter. I don't know if they still do. 7V molex-to-fan adapters also exist.

PC-Fan-Cable-Distributor-4-Way-Molex-to-4x-3-Pin-Fan-Adapter-5V-7V-2x.jpg

Reply 11 of 11, by kdr

Posted on 2022-10-11, 19:59

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psychofox wrote on 2022-10-11, 13:41:

Lots of 12v fans wont run on 5V voltage (they run but need extra push at start). So i have wired my fans between 12V and 5V wires (12v line to fan + wire and 5V to - ) the voltage between them is about 7 V, this way fan is silent and still has enough cooling power on most cases.

Oh that's a clever trick!

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