Sorry - had to step away. The homing height in M558 is locked at 229.4 and the number spat is 19.43. Still needs a teensy bit of fine tuning, but the grand picture includes printing again.

I found it.. finally.... and terribly embarrassing: X and W were reversed at the drivers. It is now homing perfectly. Now I'm going to work on the Z probe setup and will introduce a new topic if I can't get it right. For now, and to all of you who helped, Major Thanks!!! I was lost and have now been found...

That did it! So far at least... When I first got the machine, it was burning out cheap PSUs so the company's solution was to send out new beds and PSUs along with this monster MOSFET. I got an SSR while the boat was coming from China and all was well until a few days ago. The Black Widow was a heavily flawed machine but I have upgraded, rebuilt, and poured a huge amount of time and money into it - and learned a lot. It is currently a tank after this last attempt to get it right. Let's hope it works as it should - thanks repeatedly, @Phaedrux. You caught me in midair again!

Never mind - I actually found the problem on my own. Hard to believe.... !

Thanks again...

Excellent. Can I buy you a beer? Your time and effort is much appreciated.

That did it! So far at least... When I first got the machine, it was burning out cheap PSUs so the company's solution was to send out new beds and PSUs along with this monster MOSFET. I got an SSR while the boat was coming from China and all was well until a few days ago. The Black Widow was a heavily flawed machine but I have upgraded, rebuilt, and poured a huge amount of time and money into it - and learned a lot. It is currently a tank after this last attempt to get it right. Let's hope it works as it should - thanks repeatedly, @Phaedrux. You caught me in midair again!

@Phaedrux Well, that would answer that question! I'll try that first.

While I don't have another SSR on hand, I was just now able to find the machine specific MOSFET. I guess I'll be trying that out next.

The thermistor readings remain consistent. Trying to heat the hot end to 250 and the bed to 80, it reaches the target temp and gradually loses temperature until it faults - as if it can't somehow maintain that level. The temperature graph is steady and solid, reflecting exactly what is happening. Could it be the SSR is failing? The wiring all looks good and it has worked solidly for appx. 5 years. It has to be either the bed or SSR I think. And as the bed is new....
that's why I'm here trying to figure this out.

Thanks, @Phaedrux - I try the PID tune....

While writing the above, the heater faulted again:

rror: Heater 0 fault: temperature excursion exceeded 15.0°C (target 80.0°C, actual 64.6°C)

@Phaedrux said in Blinking bed heater LED, no heat:

M98 P"config.g"

M98 P"config.g"
HTTP is enabled on port 80
FTP is disabled
TELNET is disabled
Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 365C
Warning: Heater 1 appears to be over-powered. If left on at full power, its temperature is predicted to reach 852C

	M122
=== Diagnostics ===
RepRapFirmware for Duet 2 WiFi/Ethernet version 3.1.1 running on Duet WiFi 1.02 or later
Board ID: 08DGM-9T6BU-FG3SJ-6J1FA-3S46Q-1VWHD
Used output buffers: 3 of 24 (21 max)
=== RTOS ===
Static ram: 27980
Dynamic ram: 93904 of which 100 recycled
Exception stack ram used: 264
Never used ram: 8824
Tasks: NETWORK(ready,368) HEAT(blocked,1224) MAIN(running,1824) IDLE(ready,80)
Owned mutexes: WiFi(NETWORK)
=== Platform ===
Last reset 00:02:13 ago, cause: power up
Last software reset at 2020-10-26 17:37, reason: User, spinning module GCodes, available RAM 8692 bytes (slot 0)
Software reset code 0x0003 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x0441f000 BFAR 0xe000ed38 SP 0xffffffff Task MAIN
Error status: 0
MCU temperature: min 15.4, current 21.2, max 21.3
Supply voltage: min 23.9, current 24.1, max 24.4, under voltage events: 0, over voltage events: 0, power good: yes
Driver 0: standstill, SG min/max not available
Driver 1: standstill, SG min/max not available
Driver 2: standstill, SG min/max not available
Driver 3: standstill, SG min/max not available
Driver 4: standstill, SG min/max not available
Date/time: 2020-10-30 15:28:43
Cache data hit count 231726101
Slowest loop: 28.97ms; fastest: 0.12ms
I2C nak errors 0, send timeouts 0, receive timeouts 0, finishTimeouts 0, resets 0
=== Storage ===
Free file entries: 10
SD card 0 detected, interface speed: 20.0MBytes/sec
SD card longest read time 3.7ms, write time 21.3ms, max retries 0
=== Move ===
Hiccups: 0(0), FreeDm: 169, MinFreeDm: 169, MaxWait: 0ms
Bed compensation in use: none, comp offset 0.000
=== MainDDARing ===
Scheduled moves: 0, completed moves: 0, StepErrors: 0, LaErrors: 0, Underruns: 0, 0  CDDA state: -1
=== AuxDDARing ===
Scheduled moves: 0, completed moves: 0, StepErrors: 0, LaErrors: 0, Underruns: 0, 0  CDDA state: -1
=== Heat ===
Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1 -1 -1
Heater 1 is on, I-accum = 0.0
=== GCodes ===
Segments left: 0
Movement lock held by null
HTTP is idle in state(s) 0
Telnet is idle in state(s) 0
File is idle in state(s) 0
USB is idle in state(s) 0
Aux is idle in state(s) 0
Trigger is idle in state(s) 0
Queue is idle in state(s) 0
Daemon is idle in state(s) 0
Autopause is idle in state(s) 0
Code queue is empty.
=== Network ===
Slowest loop: 32.39ms; fastest: 0.00ms
Responder states: HTTP(2) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0), 0 sessions
HTTP sessions: 1 of 8
- WiFi -
Network state is active
WiFi module is connected to access point 
Failed messages: pending 0, notready 0, noresp 0
WiFi firmware version 1.23
WiFi MAC address ec:fa:bc:25:34:b1
WiFi Vcc 3.38, reset reason Unknown
WiFi flash size 4194304, free heap 21456
WiFi IP address 192.168.1.194
WiFi signal strength -54dBm, reconnections 0, sleep mode modem
Socket states: 0 0 0 0 0 0 0 0

0:/sys/config.g
; Configuration file for Duet WiFi (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.1.4 on Mon Oct 26 2020 14:50:36 GMT-0600 (Central Standard Time)

; General preferences
G90                                                ; send absolute coordinates...
M83                                                ; ...but relative extruder moves
M550 P"BW Newest"                                  ; set printer name

; Network
M552 S1                                            ; enable network
M586 P0 S1                                         ; enable HTTP
M586 P1 S0                                         ; disable FTP
M586 P2 S0                                         ; disable Telnet

; Drives
M569 P0 S1                                         ; physical drive 0 goes forwards
M569 P1 S1                                         ; physical drive 1 goes forwards
M569 P2 S1                                         ; physical drive 2 goes forwards
M569 P3 S1                                         ; physical drive 3 goes forwards
M584 X0 Y1 Z2 E4                                   ; set drive mapping
M350 X16 Y16 Z16 E16 I1                            ; configure microstepping with interpolation
M92 X80.00 Y80.00 Z400.00 E1675.00                 ; set steps per mm
M566 X900.00 Y900.00 Z60.00 E1800.00               ; set maximum instantaneous speed changes (mm/min)
M203 X720000.00 Y720000.00 Z600.00 E3600.00        ; set maximum speeds (mm/min)
M201 X1000.00 Y1000.00 Z1000.00 E2000.00           ; set accelerations (mm/s^2)
M906 X800 Y800 Z800 E400 I30                       ; set motor currents (mA) and motor idle factor in per cent
M84 S30                                            ; Set idle timeout

; Axis Limits
M208 X0 Y0 Z0 S1                                   ; set axis minima
M208 X320 Y205 Z310 S0                             ; set axis maxima

; Endstops
M574 X1 S1 P"xstop"                                ; configure active-high endstop for low end on X via pin xstop
M574 Y1 S1 P"ystop"                                ; configure active-high endstop for low end on Y via pin ystop
M574 Z1 S1 P"zstop"                                ; configure active-high endstop for low end on Z via pin zstop

; Z-Probe
M558 P0 H5 F120 T6000                              ; disable Z probe but set dive height, probe speed and travel speed
M557 X15:215 Y15:195 S20                           ; define mesh grid

; Heaters
M308 S0 P"bedtemp" Y"thermistor" T100000 B4036     ; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0                              ; create bed heater output on bedheat and map it to sensor 0
M307 H0 B0 S1.00                                   ; disable bang-bang mode for the bed heater and set PWM limit
M140 H0                                            ; map heated bed to heater 0
M143 H0 S120                                       ; set temperature limit for heater 0 to 120C
M308 S1 P"e0temp" Y"thermistor" T100000 B4036      ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1                               ; create nozzle heater output on e0heat and map it to sensor 1
M307 H1 B0 S1.00                                   ; disable bang-bang mode for heater  and set PWM limit

; Fans
M950 F0 C"fan0" Q500                               ; create fan 0 on pin fan0 and set its frequency
M106 P0 S0 H-1                                     ; set fan 0 value. Thermostatic control is turned off
M950 F1 C"fan1" Q500                               ; create fan 1 on pin fan1 and set its frequency
M106 P1 S1 H1 T45                                  ; set fan 1 value. Thermostatic control is turned on

; Tools
M563 P0 S"Extruder" D0 H1 F0                       ; define tool 0
G10 P0 X0 Y0 Z0                                    ; set tool 0 axis offsets
G10 P0 R0 S0                                       ; set initial tool 0 active and standby temperatures to 0C

; Custom settings are not defined

; Miscellaneous
M501                                               ; load saved parameters from non-volatile memory
M911 S10 R11 P"M913 X0 Y0 G91 M83 G1 Z3 E-5 F1000" ; set voltage thresholds and actions to run on power loss
T0                                                 ; select first tool

I have not PID tuned the bed since replacing it. The PSU terminals are all tight. The bed connector is factory new (except where I changed terminals for the thermistor). In this moment of checking everything again, it is all working properly. The lowest voltage drop when all things are on simultaneously is 23.6 but it is a momentary drop and usually varies between 23.7 and 24.1
That's a lot of information! Thanks for your efforts! Dean

40w hot end (new Maxiwatt 24v) and not sure on bed. However, this is a combo I've been using for a long time and the Meanwell 600 is overkill generally. I'll try to get the bed info.
Yes, I get a fault message about the 15 degree disparity when the bed stops heating and cools below target temp.
Bed = 250w

Duet 2, RRF3.1.1, via DC-DC SSR connected through the PS. I have used this setup for several years and recently overhauled the printer with a new Duet (maybe 6 ms. old) and a whole new heated bed original to the Tevo Black Widow. The bed was soldered incorrectly at the connector with the thermistor leads in the wrong location. I switched around the connector leads to the Duet and everything was working well. However, the heater LED on the board started blinking fairly rapidly two days ago and goes into a fault mode when simultaneously heating the hot end. I think the blinking is when it reaches temp and is maintaining it at that level, Then faults to off when adding the extra load from the hot end. So - maybe an overloaded/tired PS? It is a 5 y.o. Meanwell 600...

The title says it all.