power interface from adapter vs USB

I have an old Saffire 6 USB interface that is shutting itself off from time to time, often just a few seconds after starting sending sound through it. I then have to reboot computer and then it occationally shuts off another 2-3 times. Not fun at all and a real inspiration killer.
Maybe something is wrong with the interface, but I think it is a power supply issue. It started a couple of years ago when I got an extra SSD drive, and my Dell optiplex is known for have a limited power supply that isn't commutable. I need my all my hard drives and can't afford a new computer at the moment, so I am looking for other possible solutions.
 
The Saffire 6 USB is bus-powered with no possibilities to power up with an adapter. I have no idea how it works, but will an interface with a power supply (adapter) come around the shutting off issue I have with my Saffire? I have googled this a lot, not finding other than make the power settings in W7 optimized for the interface which I've done (even a setting that prioritize power to the interface - yet the only thing being shut off is the interface..!)

Leizer
... I think it is a power supply issue. It started a couple of years ago when I got an extra SSD drive, and my Dell optiplex is known for have a limited power supply that isn't commutable. I need my all my hard drives and can't afford a new computer at the moment, so I am looking for other possible solutions...

A under-powered power supply could very well be the problem.  Those stock Dell power supplies are not meant to handle an additional 3+ drives/devices.
 
It's easy enough to test if this is the case.  Disconnect the power leads to all but your system drive. Reboot, and play regular audio (say, an mp3) through the Saffire... If it runs without shutting off, then there's your problem.  (You can always upgrade just the power supply).

tlw
What’s the SDD getting power from? Is it a SATA one with the power coming direct from the SSD or an external USB one without a dedicated power supply of its own?

I guess SATA then, it's an internal SDD.
 

tlw
Is there anything else sharing the USB port with the interface?

What is connected to the PC using USB and are their any hubs involved? If hubs are being used do they have power supplies?

Do other USB bus powered things work OK?

Not sharing exactly the same port, but I have the old USB1.1 interface that has some known problem with other than root hubs.
https://support.focusrite...vices-on-non-root-hubs
So I have it connected to a USB3 internal card in the back (extra accessory for getting USB3).  The USB3 card has 2 slots and actually I had a lot of power problem with it when connecting a USB3 external hard drive for backing up stuff. I think I had to disconnect the Saffire to get the drive to work. I usually not have the drive connected, just when backing up music files.
 
In the front there is 4 slots (USB2). I usually never use them, only when connecting a USB flash drive. In the back I have 5 slots and I use 2 of them: one to a deltaco USB hub with its own power adapter and in the hub I have mouse and computer keyboard connected, never any problem. In the other slot I have an iLok. Never any problem that I know of there either.
 

tlw
If you disconnect the SSD does the interface power up OK? That test may or may not work if the SSD is the boot drive, but so long as the BIOS can supply power to the USB system it should show whether the interface loghrs come on and stay on.

The hard part to seek for errors is that the interface sometimes work, sometimes not. Now for instance I have had 3-4 successfully boots in a row, sometimes there is the opposite and it looks like this is by chance/coincidence.
 
I forgot to tell about a booting up message I get around 50% of all computer start-ups: "No boot device found. Press any key to reboot the machine." After every time pressing any key it goes through to start W7 though.

JonD

Leizer
So I have it connected to a USB3 internal card in the back (extra accessory for getting USB3). 
 
In the front there is 4 slots (USB2). I usually never use them...

Move the interface to a USB2 port.  USB3 backwards-compatibility can be dicey.

I know I tried that several times before and haven't got it to work, but I tried it again. And so far it works on a generic hub in the back (63% hub power goes to the Saffire though)! I also tried on my Deltaco Hub to possibly get more power, but it didn't work there. I wonder if I changed something lately to get it to work - only thing that comes up in mind is disconnecting the Realtek audio as well as the audio on graphic card.
It seems that the USB2 4 front slots+ 6 back slots all are generic hubs, so this shouldn't be possible to get working according to this link (and hasn't work earlier either), but I will not complain...
https://support.focusrite.com/hc/en-gb/articles/206850499-Connectivity-of-USB-1-1-devices-on-non-root-hubs
 
I've checked the other USB inserts and all seems to work. Hopefully they continue doing so.
 
Thanks JonD, tlw and fireberd for your help!

JonD
My suggestion is based on USB3 ports not being 100% backwards-compatible... Nothing to do with power requirements.
 
The other audio drivers you mention can possibly interfere so, yes, they should be disabled.
 
As I mentioned before, if the problem is that your desktop is underpowered due to the stock power supply, it's easy to test by disconnecting all of the extra devices except the system drive.  Bottom line, you have to systematically troubleshoot by testing the individual systems and ruling them out one by one.

Yes, I understand that. But now, for example, I have succeded with booting up the computer and getting the interface continous working 7-8 times in a row (except the faulty deltaco hub test) so how will I know if it is working or not disconnecting things? I start to wonder if the Realtek disconnection could have been good for the PSU as well, or else my computer has a exceptionally great weekend.