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I've got a home theatre PC which I built myself and have been using for about 4.5 years now without issue - the only components that have ever needed replacing have been the case fans. Recently, I've been getting unexpected shutdowns - no warning at all, one moment it's running fine, the next it's off. This normally happens within a few minutes of powering up.

I've narrowed the cause down to the TV tuner card I use - a Hauppauge WinTV Nova-TD 500 plugged into one of the two PCI sockets. When I remove the card, the computer is fine, and happily sits there 24/7 with no issues.

The other PCI slot is occupied by a wireless network card. If I move this to the slot normally occupied by the TV card, everything is still fine. If I put the TV card into the slot normally occupied by the wireless card, the machine won't even power on.

If I put the TV card into another PC in the house - a 10 year old desktop PC with a Asus P4P800SE motherboard in it everything seems fine - drivers installed, will sit there for as long as I can be bothered to monitor it without issue.

As far as I can tell then, the problem is either down to the TV card itself or the motherboard in the HTPC (an MSI K9AGM3-FIH) But I have no idea how to narrow this down any further. Both components seem fine in isolation, but when used together they just don't work.

Can anyone suggest ways I can find out what's going on without just replacing both components?

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TV tuners eat a lot of power and power supplies get old and can start delivering bad/lower power. – Ƭᴇcʜιᴇ007 Jun 23 '12 at 18:35
@techie007 - sounds like a possibility as it has been in heavy use for the past few years. Is there any way of verifying this that you can suggest? Also, does this explain the power tripping without warning? I assume you're thinking that there's some kind of failsafe built into the PSU that trips when it's overloaded? Thanks for the suggestion - much appreciated! – Jon Jun 23 '12 at 19:29
If the power supply is more than 3-4 years old, I probably wouldn't bother to diagnose, and just replace it. In addition to whatever may be wrong or marginally unstable, there are probably some efficiency increases in newer power supplies that make it worthwhile just on that. That, and there's some peace-of-mind in knowing your new power supply won't be slowly/secretly supplying "slightly off" power to your computer. – killermist Jun 24 '12 at 17:09

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