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Solved!

blinking red light on motherboard

HP Recommended
HP Z420v2
Microsoft Windows 10 (64-bit)

Just received a new (refurbished) motherboard from my usual supplier - yes, it's v2. Tested & Passed.  This is my 7th or 8th system I've built successfully (except this time) using the HP Z420v2 motherboard. Red light near tiny rear power button flashes. 

Pretty much everything is stock:

*16GB HP DDR3 Server RAM in the recommended slots. 

*stock HP 700 watt power supply

*stock NVIDIA QUADRO FX 380 graphics card, 2 DVI connectors

*Samsung 1TB SATA SSD properly connected

The only deviation is the LEPA closed-loop, Liquid cooled, CPU cooler, which I have used successfully several times before, fan & pump connected. Rear MEM fan connected, front fan connected. 

Any thoughts as to what might be the cause, what I might check? Puzzled. Thanks in advance for your help. 

 

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does the front power button light flash? if so what is the flash sequence

 

have you done a power supply BIST (Built In Self Test)

 

are the components like cpu/ram known pre tested items or just  new untested items

 

recheck the closed loop cooler, improper mounting can apply excessive pressure to the cpu socket causing it not to sit flat in the socket (loosen the mounting screws, then tighten in a crosshatch pattern till the cooler block does not easily move)

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Interested in the water cooler... do you mind sharing the exact model you chose, and any unique mounting you did?

 

The HP air coolers for the Z420/Z620 use a standard PWM fan pinout except HP adds a short ground to ground jumper wire at the plug end from pin 1 to pin 5.  Hence, the pinout for the fan becomes ground/ +12VDC/ RPM sense/ PWM control/ ground, via a 5-hole plug rather than the usual 4 for PWM fans.

 

The fan on your water cooler may simply need a ground jumper from pin 1 to pin 5.  It is pretty easy to find a 5-pin HP plug end included with a proper HP CPU fan being sold on eBay.  I also posted on getting a pack of them from Mouser.com.  You can extract the original wires from your 4-wire plug, keep them carefully in proper order, and then add in a junker silver metal fan plug end for wire 5 and jump solder it over into wire 1 (ground).  Having said (and done) that mod I note that the CPU cooling fans HP uses run usually pretty fast at unbraked +12VDC, but then are ramped down by a strong HP PWM braking applied by the motherboard.  Hence, for example, a nice low RPM Noctua PWM fan if used then gets forced down to a too-slow RPM. 

 

Not sure of the diameter of the stock fan on your water cooler, but the HP ones in the ZX20 CPU heatsinks are usually 92mm and may be 25-15mm thick.  I can check for you... I have a bunch here.  Using one of those HP originals would be ideal because they are matched to the HP motherboard's PWM braking and should end up about the right RPM for your water cooler.  Not seeing the 5th pin grounded will throw a motherboard error.... maybe cause of your blink.  That ground is the way the motherboard knows all is well.

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SDH, thanks for getting back to me. After almost 30 years in high-tech I'm beginning to believe in Dark Magic & Gremlins when it comes to building computers. I've probably built 80 systems over the past 25 years and I've yet to have everything working perfectly the first time. I fiddled with this and fiddled with that and low and behold (after several memory changes) the HPZ420v2 booted up, steady blue light, recognized all 64GB RAM, great benchmarks. Who knows? 

Regarding a Liquid Cooled, close-loop CPU cooler I like two models. LEPA is the cheapest, works great, has sturdy hoses (look like car radiator hoses). LEPA All-In-One AquaChanger 240 Liquid CPU Cooler 240mm LPWAC240-HF For Intel MB. The other one I've used several times is: Cooler Master MasterLiquid LC240E RGB Close-Loop AIO CPU liquid cooler. Both have 240mm radiators. I added two additional fans in a push/pull configuration. On the HPZ420 case I had to remove all the steel below the DVD optical Drive bay. This allowed me to place the 240mm radiator up against the lower front panel. Brings cool air in over the radiator and exhausts warm air into the main cavity of the workstation. I use an Acrylic panel with two 120mm exhaust fans screwed to the panel to blow out the heated air. I attach the Acrylic panel with tiny dot magnets all around the perimeter of the panel - snaps onto the case. Since I don't use mechanical drives the magnets don't have anything to interfere with. I can send pictures if you like. 

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Jekemi2013,

 

Thanks for the update, and it is great to hear you made the breakthrough.  I agree on the gremlins... persistence can scare them away.  It would be great to see some pictures if you could do that.  In these strange times we seem to have some extra time for such projects.  I know that our friend Bambi is using the internally mounted all-on-the-processor HP liquid cooling approach to good effect.  It would be valuable to see your approach also.

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