ReadNAS Pro 6 stuck on 'ReadyNAS' when booting

There are actually a multitude of things that can cause that, as the "ReadyNAS" message is stored in the display and the NAS just needs +5V (and not very well regulated +5V) to display that.  But StephenB​ is correct that the power supply is the most common.   I've bought (and then repaired and resold) several with that symptom, and only one in the 6 I bought had something wrong other than the PSU. 

The 6-bay legacy units (Pro and Ultra 6 models)  actually have a standard pin-out and a standard ATX supply can be used externally with no pin-out modification.   If you have one available (even if you need to temporarily "borrow" it from a working PC), you can quickly find if that's the issue doing that.  If you use an external supply for a long period (if you just want to get your files and then plan to ditch the NAS, for example), then make sure you take precautions to insure the fan moves enough air over the drives.  Cover the PSU fan hole and any gaps where the cable comes out with masking tape.

A standard SFX supply will work as an internal replacement, but most need a 24-pin extension and more 4-pin  MOLEX connectors.  While the original is 250W, it has more +12V wattage than most 250W, so I recommend at least a 350W one.

While it used to be a bit cheaper to buy a standard supply and add those features to it, there is a pre-modified one available on eBay that now has a price that's about what it would cost to do it yourself and is a whole lot easier.

If it's not the power supply, there isn't a lot more that's user serviceable.  RAM and the CPU are it.  A bad CPU is rare, but bad RAM is a possibility.

Thanks for your response.  Any recommendation for a 6-bay USB chassis that you might be familiar with?

BSMorgan wrote:

My ReadyNAS Pro6 isn't booting and is stuck on the logo.

Usually that indicates that the power supply has failed.  It can be replaced - Sandshark​ can give you some guidance if you need it.  You can find them for ~ 100 $USD (or less).  Stock supplies usually need a 24-pin extension and more MOLEX connectors,  but you can also find some PSUs pre-modified for ReadyNAS.

BSMorgan wrote:

Assuming that those don't work, would/should I be able to use another chassis of the same model, put my disks into it in order, and get everything to boot back up?

If you are still using 4.2.x firmware, then you can get a replacement Pro 6, Ultra 6 chassis, or Ultra 6 plus. 

OS-6 platforms are also possible- RN316,RN426, RN428, RN516, RN526, RN528, RN626, RN628.  Even if your NAS is still running 4.2. firmware, the array can be mounted read-only in the OS-6  platforms.  The OS-6 platforms would be somewhat newer, as Netgear stopped manufacturing Pro and Ultra models back in 2013.   

A less expensive approach is to get a 6-bay USB chassis and connect that to a PC.  Then you use either Linux (including the Windows WSL package), or RAID recovery software to access the files.