hi friends Pin 8 not turn on for heated bed

my board is KFB 3.0
all is active(endstops - probe z - bed leveling)
but heated bed on pin 8 not power
This shows the error:

start
Printer is now online.
echo:Marlin 2.0.5
echo: Last Updated: 2020-03-14 | Author: (none, default config)
echo:Compiled: Jul 2 2023
echo: Free Memory: 5587 PlannerBufferBytes: 1136
echo:Hardcoded Default Settings Loaded
echo: G21 ; Units in mm (mm)
echo:; Filament settings: Disabled
echo: M200 D1.75
echo: M200 D0
echo:; Steps per unit:
echo: M92 X100.00 Y100.00 Z400.00 E98.20
echo:; Maximum feedrates (units/s):
echo: M203 X300.00 Y300.00 Z5.00 E25.00
echo:; Maximum Acceleration (units/s2):
echo: M201 X1000.00 Y1000.00 Z50.00 E10000.00
echo:; Acceleration (units/s2): P R T
echo: M204 P1500.00 R1500.00 T1500.00
echo:; Advanced: B S T J
echo: M205 B20000.00 S0.00 T0.00 J0.01
echo:; Home offset:
echo: M206 X0.00 Y0.00 Z0.00
echo:; Auto Bed Leveling:
echo: M420 S0 Z0.00
echo:; Z-Probe Offset (mm):
echo: M851 X10.00 Y10.00 Z0.00
Error:Thermal Runaway, system stopped! Heater_ID: bed
[ERROR] Error:Thermal Runaway, system stopped! Heater_ID: bed

Errorrinter halted. kill() called!
[ERROR] Errorrinter halted. kill() called!

Guide me
thanks

KFB3.0specification.pdf

D8 is correct

It looks like there are two fuses behind the power plug. I would check those have continuity

Thank you for your reply..
You mean these 2 fuses: F2 - F4 ?
These two fuses are for short circuit.
The board turns on without any problem
Only heated bed won't activate and I don't know what others did..
I can't think of anything now..
And I don't know exactly where the problem is
please HELP ...

There are only a few possibilities

blown fuse, dead mosfet or a faulty bed or the bed wiring.

I do however see your running marlin 2.0.5 this is very old. released Mar 14, 2020

I strongly suggest yo upgrade to marlin 2.1.2.1

Edited 2 time(s). Last edit at 07/03/2023 07:00PM by Dust.