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Replaced PSU, now USB ports have power, no data?


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So my aging, but good enough, HP lost it's 2nd Power Supply. I tried to reboot, the PSU fans stopped turning, no apparent power to the system. So I ordered a Corsair CMPSu-400CX to replace the 350W PS. Got it, plugged everything in, except the 4pin socked on the MB near the PSU, this PS had 2 4 plug adapters on the same 'cable'. The look the same, have the same colors on them, black & yellow, the old PS only had one of these. the 24pin main conector was a sold 24 pins, not a 20+4. So I pluged 1 in, left the other hanging, power up the system, and all is good!


Well until I tried to retieve data on an external HD & Thumb/flash drive. I got USB Device not recognized messages on all on board USB ports for any data device I pluged in. (4 in the read, 2 in the front plus a 4-in-1 card reader). They power a device (ie the thumb drive lights up) and the USB mouse works fine.


At the time I was using Vista 32bit MCE. Safe mode made it seem like it might have been a software issue, so I did a complete system restore to XP MCE, but no luck. Of course I check all the MB connections, all seem good. The front panel 1394/firewire port works fine (also routes to a MB connection).


So any suggestions? Did the old PS fry part of the USB circitry? Did the new one? Something else to try?


PS I did insert a PCI-USB 2.o card, and devices work fine from it. I'd rather leave that slot open to help keep the video card cool, and I'd love to get my card readr working again.



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Connect the EPS/ATX12V 8-4 pin to the 4 pin socket on the motherboard.


Thanks I did connect 1 of the 2 4pins, then swapped them, same problem.


PS what does this 4pin socket power up? (sadly the last PC I built was in the 386/486 days)

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I also have USB ports issues. hey sort of works but I get lagging and sometimes error messages.



My PSU are assembled on anti vibration pads so my question simply is. Is it necessary for the computer case to be connected to earth? If so should a specific wire be used?

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Hello again!


I agree that there probably is no problem with the PSU. It was more a general question.


Is it necessary to have metal to metal contact between PSU and computer case? or doesn't it matter? I thought that the power cord was the one conntecting the case to the ground.


Since I don't have good metal to metal contact I thought that maybe an exra little cord or something could be used. But if it's not needed...


Best regards,


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Thanks alot!


I was a bit worried and torqued the screws hard on the PSU when assembling it to the case but it still was this vibration dampening foam between.


So basically you are saying that the PSU could be outside of the box?


Thanks again!



Johan, Sweden

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