Printer resets Upon bed Heating

bobot

I have an A5s that's printing normally with marlin  V2.0D firmware for some time and then the printer halted at 70%. I power cycle the printed then it showed "thermal runaway......" i didn't have time to take pic of the error msg.  it boots normally, but when i try to heat up the bed to 40deg, it resets itself. Heating the hotend is Ok. 
what i have done so far are...
Check bed wiring connections
Replaced bed thermistor
thermistor reads around 70kohms @ 35deg
The heater is ok
firmware update to D-G-H then factory firmware, all same results when bed heating up.

PRONTERFACE  printing

SENDING:G0 X100.0 Y100.0 F3000

Setting hotend temperature to 185.000000 degrees Celsius.

Setting hotend temperature to 0.000000 degrees Celsius.

Setting bed temperature to 45.000000 degrees Celsius.

þàþøæøx†øø†æPowerUp +++++++++RESETS after bed heating++++++++++++++

Marlin 2.0.7.2 (2020/12/22)

echo: Last Updated: 2.0F (2020/12/25) | Author: Samuel Pinches

echo:Compiled: Dec 25 2020

echo: Free Memory: 8159  PlannerBufferBytes: 1600

echo:SD card ok

Ambient temp of bed is 35deg, heating it up to 30 to 35deg is ok but passing the ambient temp reading  resets the printer.
I tried to print with 0 deg bed heat = ok, but with base warping.

IS this a board problem???

bobot

PID TUNING

Connecting...

Printer is now online.

>>> m303 e-1 s10 c8

SENDING:M303 E-1 S10 C8

PID Autotune start

žþàþ>xføøøøæPowerUp

Marlin 2.0.7.2 (2020/12/22)

echo: Last Updated: 2.0F (2020/12/25) | Author: Samuel Pinches

echo:Compiled: Dec 25 2020

echo: Free Memory: 8159  PlannerBufferBytes: 1600

echo:SD card ok

giantrobot2001

Open it up and check all the connections.  I have another one from JG new I won't plug in until I open the case and check the plugs.  (There is a hidden set of three right behind the main assemble gantry three to the case too)  I love these machines.  I have a JGAURORA z603s and I wish it had the diamond glass like the A5S.   open it up and go over every connection, the shorts can make you need a board  . Or you may need one already.  I don't want to bash JG, but the cables are short and the connections are a known common issue - they were hurried in assembly.  I have pictures of the hot glue thread causing a connection issue.  Getting a bit jiggy in assembly, I suppose.  Beyond that I have no issues.  The proprietary board itself does pretty good considering it's right there.  I have a light inside one, It's a nice machine. I know the hotend thermistor circuit rather commonly shorts - even cause hotend runaway on the board, and of course especially handling the hotend, and you may be able to change it to the unused channel if that happens to you.  I don't have much experience to help beyond that.  The A5S has been really reliable for me and I have a couple of them... I'll finally mount one in a frame and rig it with a direct feed sooner or later.  Not for a little better quality, but mostly because it would be alot better for some of the filament types, and the tube is annoying

bobot

I already did check/reseats the connections and looks fine. Im planning to separately power and heatup the bed. Is the bed 24vdc supplied? 

Samuel Pinches

Reset on bed heating typically means a short circuit. Check that the bed clips are in the correct places otherwise they can cut into the heating elements and cause a short.