I was hit by this one today.
The problems are always worse when you've committed to an order
Just as pleppik found, the repeated flexing of the platform heater cable caused one of the wires to break completely. I'm assuming by the blackened insulation that it has been intermittent for some time and sparking due to the heater current.
A second wire is broken, but held close enough to be only occasionally intermittent, which explains my "platform too hot" errors...
Note to anyone who hasn't checked their cable yet, it is a simple check:
- Remove two bolts holding the platform on.
- Remove 4 bolts on the X-Axis cover.
- Gently lift off cover.
The cable is easily visible, and the break happened to me where the cable bends as you move the platform all the way forwards.
It has obviously been rubbing too judging by the abrasion marks on the outer insulation.
As an interim fix to get me up and running, I stripped back ~15mm of outer insulation, then ~1mm of the inner wire insulation.
Solder back together with a some heat shrink tubing and suddenly my platform heats in half the time!
Not worth the effort of a return IMHO, but not sure where I'll stand on warranty
My printer is 6 months old and has had approx. 5kg of plastic go through it - mostly 90mmx90mm prints, so the cable is being flexed a lot.
Longer term I will replace all 4 wires with flexible silicon wire as suggested by wilsonj.