Diagnose this stutter please? (Video)

How are ye...can someone have a look at this video and point me in the right direction ?

I'm trying to print a calibration cube with Pronterface, the built in Slic3r, and Marlin.
When it starts stuttering, the heated bed power stutters too, as well as the light on the Xbox PSU.

I absolutely haven't a notion what could be wrong...because it seems to intermittently occur. I don't think it's the stepper drivers overheating because i've used thermal compound to put heatsinks on them, and there's an 80mm fan blowing across the board too, which is completely open to the air rather than being in a box. The drivers don't get hot to the touch either.

Thanks in advance guys

[drive.google.com]

Kinda sounds like you have not tuned the drivers.
They may be running under current and therefore not enough torque

The heated bed going off too, and the PSU light.. that's odd.
So it do not sound like a driver adjustment issue.

The PS must be at fault. Can you put a voltmeter on it when that's happening? It may be too brief to catch that way tho.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
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Kinda solved:

I reduced the belt tension because my pulleys are running on m6 bolts in single shear so there's a lot of friction. That allowed me to reduce the Vref on the stepper drivers down to <0.3 V. Steppers are running a lot cooler now and it doesn't jump as often.

If I plug in the heated bed bed it runs fine while heating, but as soon as the bed reaches the target temp the light on the power supply goes red and the Printer stops and judders really badly again. So it seems theres some kind of issue with the PSU still, but turning down the drivers had helped somewhat