MX5 and coil whine / electrical noise?

simisker · Post by **simisker** » Sat Sep 04, 2004 7:11 am

Hi, folks!

I've recently become the proud owner of an MX5 and am encouraged by the potential I can see in it. However, my computer appears to be less enamoured with it.

When the display is active and running LCDC, the PC emits a high-pitched electronic whistling/warbling noise. More specifically -- and oddly -- this whistling tends to come from the CPU, and only when the VFD is moving characters around its screen. If I stop LCDC, the noise stops too. Whilst not loud, it's very noticeable/audible and quickly becomes highly irritating.

Has anyone else come across this, and is there a solution?

If it helps, my spec is as follows:

AMD Athlon64 3200+ [clawhammer] @2350MHz
Asus K8V
OCZ Enhanced Bandwidth Memory [1GB]
Hercules 9800 Pro [with Arctic Cooler]
Sea Sonic Super Tornado 400W PSU
Cooler Master Stacker case
2 x NEC DVD writers
1 x Hitachi 7k250 HDD
Matrix Orbital MX5 [obviously!]

I would be insanely grateful of any advice or thoughts on this irritating problem, so thanks in advance, guys!

Tom · Post by **Tom** » Tue Sep 07, 2004 9:07 am

Do you have a fan connected to the GPO of your MX5? If you do, try lowering the frequency of the GPO the fan is connected to.

simisker · Post by **simisker** » Tue Sep 07, 2004 12:48 pm

Hi, Tom. Thanks for responding!

No, at the moment I've not connected anything to the GPO - I'm still at the "let's make sure the basic operations are okay first" stage.

More internet searching on my part has perhaps shed some light on the problem. My Sea Sonic Tornado PSU utilises Passive PFC [Power Factor Correction], and this, when combined with a Radeon 9x00 graphics card can cause the PSU coils to resonate. So it's looking like it's more a problem with 'dirty' power from the graphics card, and not a problem with the MX5 [you'll be glad to hear!

]. Though why the MX5 causes the coil whine, I'm not sure. Maybe it also sends 'dirty' power back up the floppy rail to the PSU; I don't know.

For anyone else that may be suffering from this, there appear to be two solutions: Either open up the PSU and use a hot glue gun on the coils until they're completely covered and stifled by the glue; or use an Active PFC power supply instead. Given a healthy fear of all things that handle electrical power, I'm going to try an Active PFC-based PSU and report back with my findings.

[EDIT: Thought I'd try putting the graphics card and the MX5 on different/separate power cables to see if that would solve it. It hasn't. Oh well - PSU shopping I go...]

Tom · Post by **Tom** » Tue Sep 07, 2004 1:15 pm

Glad to hear you fixed your problem. If you have any questions or concerns about your MX5, please feel free to contact me.

simisker · Post by **simisker** » Thu Nov 04, 2004 2:51 pm

Update:

I'm sorry to say that I still haven't resolved the problem with my MX5 and coil whine. [now solved - see edit below!]

It makes no difference whether there's an Active PFC or Passive PFC power supply feeding it - it's still chirping/whistling away.

I have just noticed, though, that when I unplug the USB cable to the MX5, the noise stops. Of course, it won't update the display in this state, so it's still far from solved.

Ho-hum. Does anybody have any odd miraculous cures for coil whine? Or is this just a known issue with the VFDs? Is no-one else at all with a similar setup [Athlon64, Radeon 9800 Pro, MO VFD] experiencing any coil whine?

*sobs into coffee*

[EDIT: Okay, after even more research, I've found out what the problem is, and it's NOT the VFD. It's the chokes [metal coily things] on the motherboard reacting to USB input, and the only solution is to cover them in hot glue to stop them vibrating. Technology, eh - isn't it wonderful?

]