Weird Heating Issues

So, this has been plaguing me for a couple days and I even bought a new power supply to see if it would fix it. I've taken a snip of the temperature graph in the attached image. Essentially, I set the temperature to 210C and it gets up to a certain amount say 202C then drops to 198C or so and just keeps doing this in a sin wave, never actually reaching the temp. Has this happened to anyone, or do you have any ideas?

The new power supply is capable of outputting 30A, three times more than the old one. Using Slic3r and Repetier host along with Marlin firmware.

That is screaming for a PID tune . . .

- Tim

Even with a totally wrong pid tuning there should not b such a wave...
But I agree, start with the pid tuning and check the firmware settings.

Thats just odd. the wave isn't good, but its offset is even weirder..

*goes looking for trusty old tinfoil hat*

---

Master Tinkerer

Could be that an external signal is interfering, the Gen6 boards had similar issues in this regard, although not with a perfect sine wave...
Tried to get something like this with 3 different hotends but failed.
Get irratic regulations jumping all over the place but no chance for a sine wave - maybe the electronics are faulty somewhere (loose connection, bad soldering etc...)?

what is the MAX temp you have set in the firmware? It is a 4 degree difference, which I would assume is the normal heating cycle.