Gigabyte GA-5AA Problem with CPU Fan voltage \ VOGONS

Gigabyte GA-5AA Problem with CPU Fan voltage

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First post, by byte_76

Posted on 2024-09-14, 07:10

byte_76 Offline

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I have a Gigabyte GA-5AA revision 1.1 which is working fine and seems stable with the exception that the CPU fan voltage is fluctuating and results in the fan not spinning.

I measured the voltage across the pins of the CPU connector and found that it jumps up and down between almost zero volts and 9.8 volts, which was the highest that I saw.

When plug in the CPU fan, it spins briefly and then stops. Unplugging and replugging the fan can get it to spin a bit longer but it always eventually stops.

I don't know which components are part of the power circuit for the fan or where to start with troubleshooting the issue beyond what I've already done.

I've just learnt some of the basics for retro hardware maintenance, so I'm handy enough with a soldering iron and I can do the basics with a multimeter but I don't know much more about electronics.

The board has not been recapped but the caps look okay physically.

Can anyone assist me with this issue?

Reply 1 of 8, by dominusprog

Posted on 2024-09-14, 07:24

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The later socket 7 and super 7 boards usually have a temperature sensor, so depending on the temperature of the CPU it'll adjust the voltage.

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Reply 2 of 8, by byte_76

Posted on 2024-09-14, 09:53

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The cpu is definitely running hot when the fan isn't spinning. I'm sure it would start spinning under those conditions if this was sensor related.

I don't think this is normal behaviour but maybe someone else with such a board can confirm?

Reply 3 of 8, by dominusprog

Posted on 2024-09-14, 10:36

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Well, there are two transistors (Q symbols) and one resistor (R) in that area, check the voltage for both inputs and outputs.

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Reply 4 of 8, by Horun

Posted on 2024-09-14, 16:51

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It should be solid 12v from what I see, the traces appear to be 12v and ground. Also it is a 2 pin fan header not a 3 with tach/sensor pin (like GA-5AA rev 3.2 and FIC VA-503+).
Just use an adapter for 12v fan to molex and see if it spins proper...

Last edited by Horun on 2024-09-14, 17:07. Edited 1 time in total.

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Reply 5 of 8, by Nexxen

Posted on 2024-09-14, 17:04

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Trace it back to the source. It could also be a bad cap in between or a resistance dying.

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Reply 6 of 8, by byte_76

Posted on 2024-12-17, 15:11

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I resolved the issue by replacing the two transistors just below the connector.

Reply 7 of 8, by Nexxen

Posted on 2024-12-17, 15:16

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byte_76 wrote on 2024-12-17, 15:11:

I resolved the issue by replacing the two transistors just below the connector.

Could you post a pic? For the records.
Maybe it'll be useful in the future.

Reply 8 of 8, by byte_76

Posted on 2024-12-17, 15:46

byte_76 Offline

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A pic was in my first post above. (The pic with the connector where you can see the two transistors just below it. Q17 and Q18)

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