000: HEX8 0: 260 1000/ 800mV | 0.000/ 0.000h/s | A:0 R:0/0.00% HW:0/0.00% WU:0.0/m
I'd expect to see that if the chips didn't have enough power to fire up. 1000mV should be enough though.
I cannot get mine started under 850mV and they look exactly like that.
If you're sure your PSUs are providing power, maybe the fuse is blown on the circuit board, or you got some really lazy chips?
I don't get where taht 800mV comes from, but will take a visual inspection look on board now...
don't know what to look for.. but tried both pci-e power separately, any of them starts fans, so they should be ok, connected all cables again, cgminer will detect hotplug but that is it:
cgminer version 4.0.0 - Started: [2014-03-07 23:04:03]
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(5s):0.000 (avg):0.000h/s | A:0 R:0 HW:0 WU:0.0/m
ST: 0 SS: 0 NB: 2 LW: 343 GF: 0 RF: 0
Connected to stratum.btcguild.com diff 256 with stratum as user xxx_hex8a
Block: 3bb82dcf... Diff:3.82G Started: [23:07:38] Best share: 0
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[U]SB device management [P]ool management [S]ettings [D]isplay options [Q]uit
000: HEX8 0: 260 1000/ 800mV | OFF / 0.000h/s | A:0 R:0/0.00% HW:0/0.00% WU:0.0/m
001: HEX8 1: 260 1000/ 800mV | 0.000/ 0.000h/s | A:0 R:0/0.00% HW:0/0.00% WU:0.0/m
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[2014-03-07 23:03:45] Started cgminer 4.0.0
[2014-03-07 23:03:46] Probing for an alive pool
[2014-03-07 23:03:56] Waiting for work to be available from pools.
[2014-03-07 23:04:02] Pool 0 difficulty changed to 2
[2014-03-07 23:04:02] Pool 0 difficulty changed to 256
[2014-03-07 23:04:02] Network diff set to 3.82G
[2014-03-07 23:04:03] Work available from pools, resuming.
[2014-03-07 23:04:08] API running in IP access mode on port 4028 (13)
[2014-03-07 23:06:04] HEX8 0 failure, disabling!
[2014-03-07 23:07:10] Hotplug: hexminer8 added HEX8 1
[2014-03-07 23:07:38] Stratum from pool 0 detected new block