Water has entered the motor block and my new power supply when connected the two red leds flash alternately. I suspect the printed circuit board within the motor block is damaged.Can I purchase one ?

This is a common problem for LG 42LN5xxx & 47LN5xxx LED TVs, the problem is defective LED back lights strips, it has nothing to do with main power supply & the main board.

First, always check carbon brushes on main motor especially if the appliance is in use for several years.

Five times the red alarm means a problem with the engine washing.
So, could be:

E51 - Motor power triac short-circuited.
Current leakage from motor or from wiring; Main PCB faulty
E52 - No signal from motor tachometric generator.
Wiring faulty; Motor faulty; Main circuit board faulty.
E53 - Motor triac sensing circuit faulty (wrong input voltage to
microprocessor). Main circuit board faulty.
E54 - Motor relay contacts sticking (high voltage level when
the relay switches to OFF).
Current leakage from motor or from wiring; Main PCB faulty;

Rapid reading last alarms:
Press the START/PAUSE button and the nearest option button simultaneously (4 and 6) for at least 2 seconds: the LEDs initially switch off, and then display the flashing sequence indicating the last alarm.
Dado

Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis. http://electro-medical.blogspot.com/
To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main board.

Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis. http://electronicshelponline.blogspot.com/ To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main board.

The cartridge reach end of life, replace the fuse for a new one (63mA or 100mA)

The common fault often points the problem being to the power supply or the main printed circuit board.
If you are tech-savvy, you can open the back of the unit and measure, using a multimeter, the voltages from the power supply printed circuit board as well as the main printed circuit board, if the power supply is sending insufficient voltages, its common that you will get the flashing red lights.
Also check for any blown capacitors on the power supply as well as any shorted resistors. I hope this helps.

I always found the problem to be either a combo of the x-sus printed circuit board and the y-sus printed circuit board. It is also very worth checking out your poer supply circuitry as well. Good Luck.

The problem is in the power supply circuit of controller PCB. Replace C9 (680uF/10V) with a new one.

Hi Franceso, plz specify
Is it powering ON ?
Which LED is glowing?
These leds are there on the front panel :

1 Power On/Standby button
2 System power LED
Green = Power on
Amber = System shut down, but power still applied
Off = No power

3 Internal health LED (Wave sign in BOX)
Green = Normal
Amber = System degraded. To identify the component in a degraded state, refer to system board LEDs.
Red = System critical. To identify the component in a critical state, refer to system board LEDs.
Off = Normal (when in standby mode)

4 External health LED (power supply)
Green = Normal
Amber = Power redundancy failure
Red = Critical power supply failure
5 NIC 1 activity LED Green = Network link
Flashing = Network link and activity
Off = No link to network.
6 UID LED Blue = Activated
Flashing = System remotely managed
Off = Deactivated
7 UID button

If it is Internal health led then any internal h/w issue is suspected.
If it is external health led then any power supply or power source related issue is suspected.
Also check the status of the server & its IML (Integrated Management Logs) in ilo (Integrated Lights Out ) if it is configured. (2nd RJ45 port in rear)

Also make sure the cabinet is properly closed.

Ok 7 red blinking led, remove the back cover of the TV. Looking at the power supply in the upper left of power supply. If everything is working fine you will see a solid green led if there is an error, you will see this light blinking also. Right below this led on the power board you will see a list of numbers 1-13 this will give u the problems that this led flashing problems are. More and likely u will have a problem with VSET or VSCAN. Which is connected to the Y-Main and Y-buffers,( the board that is too the left of the power supply if u look on the small print on this board you will see that it reads. 42HDV4 Ymain and the 2 small boards connected to it are Y buffers. To be sure that this board is bad if the TV keeps going into error protection. unplug the power supply and wait for the led to stop flashing. Disconnect the cable that plugs into Y-Main from the Power Supply. It should stay running. If u remove this board and look underneath u should be able to see where this board is getting hot. Easiest fix is to order a replacement. Y-main assembly.