Raspberry pi 3 just stops responing.

[skywatch]

For some reason this happens regularly to me.

SETUP AND WHAT I HAVE DONE SO FAR.......
rpi 3 running latest and updated raspbian from usb connected Kingston ssd hdd (previously tried several brand new Sandisk uSD cards and same result).
Tried many different power cables and power supplies. Now using RS components 5V 6A with extra smoothing and decoupling caps added.
Tried multiple raspberry pi 3s with same result.
Static IP address is used via wired gigabit ethernet.
Also connected is a USB serial adapter connecting to an arduino pro mini that runs as a mysensors gateway for mycontroller system.
A large heatsink has been added with additional cooling fan which is temperature controlled via a small python script.
Generally it runs the cpu at about 5-10%.

THE PROBLEM
It all works fine for many days or weeks and then just stops working.
It won't respond to pings, ssh or http. The activity led on the hdd no longer blinks indicating no read/write of the drive.
The 'activity' (green) led on the pi 3 flashes regularly about once a second and the pi network port green led flashes occasionally.

I have no monitor attached to this pi 3 to see what is happening locally. A power off/power on usually brings it back working again until the next failed state.

If anyone can help make this work reliably I would be soooo grateful.

[DougieLawson]

The green LED flashing means it's not booted. The stuff on your SDCard is either not correctly written or too old for the Raspberry you're trying to use it on.

Get yourself a copy of plain Raspbian https://downloads.raspberrypi.org/raspbian_latest (don't unzip it)
Get yourself a copy of Etcher https://www.balena.io/etcher/ (for Windows or Mac)

Use Etcher to write Raspbian to your SDCard and try again.

[skywatch]

Thanks for the reply.

The green LED flashing means it's not booted.

Which green flashing led? The network one or the activity one?
How does it become 'not booted' after days or weeks of running? What is the likely process for this please?

The stuff on your SDCard is either not correctly written or too old for the Raspberry you're trying to use it on.

Please re-read the first line of my OP. But to repeat - the latest version fully updated/upgraded and it boots without issue, it just doesn't stay working for some reason.

Use Etcher to write Raspbian to your SDCard and try again.

As stated above as clearly as I could, it is not using an SD (or micro SD card) at all - It is running from a Kingston SSD attached via USB.

I also just realised that this happens on another pi3 running boinc/seti@home work units. Exactly the same issue. Also by coincidence another pi3. This one too tried SD and SSD. Still get the issue.

[skywatch]

Anyone can help please?

Seems like the same issue reported here also viewtopic.php?f=28&t=238211&p=1458468#p1458468

[0x0luke]

Do you have another Linux computer you could plug the ssd into?

Do you have the ability to connect it to a monitor? Do you get the splash colour screen when starting it up?

[PhatFil]

I had similar head scratching issues with my Pi(es) one or more would just not be accessible after weeks of service.
wifi or lan access dint seem to make a difference .

i flashed a number of minimal installs and only required installations, - no change, the odd loss of service still happened on occasion.

It became more evident after i adopted mqtt for home automation as things stopped working..

In the end i discovered it to be a router issue. and a router reboot was all that was needed to provide the ssh access etc that earlier failed.