TX750 fan motor problem

Hello, dear Corsair Support Team.

I have a problem with my brand new PSU. Its fan makes loud buzzing sound during work periodically.

PSU works fine when the fan isn't spinning. Also it works pretty well, when system becomes under load. It begins to spin quite noiselessly. But when after that system load falls down to idle level, the fan lowers its rpm and utters buzzing sound during 1-2 mins till it finally stops.

Also that could happen when system is under slight load, for example during web-surfing. But, in this case I can't point the exact scenario the sound comes out, but it lasts during long time too.

So, here are results of my research :-P

As I could see in different threads, the fan controller in PSU have two conditions to start/stop the fan: power consumption(about 40%) and temperature(about 50°C). So, if one of these conditions becomes true the fan controller puts some voltage to the fan. And inversely, when both conditions become false, the fan controller puts no voltage to the fan.

The scheme is pretty simple and understandable, but let's take a closer look to the power-on state of the fan. I don't know for sure, but I guess that the fan controller has different voltage levels for spinning fan. It switches between them depending on the same conditions it uses to start/stop the fan (power load/temperature). So, the more power system uses or the more temperature PSU becomes - the fan controller switches to next voltage level and fan spins faster. Our object of investigation is the first non-zero voltage level, the fan controller switches to, when it decides to begin spinning.

The buzzing sound comes out when voltage fed to the fan is not enough to make it spin. This sound will occur either fan is idle or is spinnig, when it starts to get this minimal voltage level. And, of course, when fan is fed enough with voltage, it spins silently.

This explains my two cases of buzzing sound.

In the first case system gets over 40% load (maybe 50%-60%), so fan, I guess, skips the first voltage level, and starts to spin silently. After system unload, the fan controller switches to the first non-zero voltage level, and fan begins to buzz at low rpm for 1-2 min.

In second case, I suppose, system gets slight overheated (more 50°C) during a long time. And the fan controller switches to the first state, and fan begins to buzz again, till the temp goes to normal value :-P After some time the process repeats.

So the problem could be in the one of two cases:

1. PSU has bad fan, that isn't able to rotate at such low rpm.

2. PSU has bad fan controller, that put too low voltage to fan.

I have already changed my first TX750 with exactly the same problem in the store I bought it. And now, the second TX750 has the same issue. So, is it bad batch, or should I upgrade it to higher-end HX or AX series via RMA?

As I could see in different threads, the fan controller in PSU have two conditions to start/stop the fan: power consumption(about 40%) and temperature(about 50°C). So, if one of these conditions becomes true the fan controller puts some voltage to the fan.

Sort of...It can be any combination of the two. It doesn't have to be one or the other.

So the problem could be in the one of two cases:

1. PSU has bad fan, that isn't able to rotate at such low rpm.

2. PSU has bad fan controller, that put too low voltage to fan.

Correct! Either way you should have it replaced. If you can swap it out at your reseller's I would start there. If that is not an option then just use the link on the left to request an RMA.

Thanks for a such quick support, peanutz94.

I mentioned that, I've already changed my psu in local store, and it has the same issue. I don't want to bother them anymore, because I think, this is not their fault. So, is the probability that RMA changed PSU would be ok higher, than local store changed? Or it would be better to upgrade to higher level PSU to be sure everything is all right?

RAM GUY, thank you for your reply.

I'm going to try to submit an RMA request next week.