How to replace the led display board... bought the part, need instructions

If it is an led display, it might have a display driver integrated circuit that has gone bad. More likely, though the driver might be part of the microprocessor. Either way, you'll either need to have an electronics technician fix it, or replace the circuit board.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/david_29ad5d1dd86564b0

In many cases , cockroaches are found to habit within specially when not used and can spoil the main board, panel display and connectors. Remove the front panel and board and confirm and if so you need to wash the board and reset. Also it can be due to failure of the display or drive from the board

The keypad control board will need to be replaced, the cost for the part alone is $100.00 or more.

The display driver is faulty. A replacement display board may still be available. Try www.espares.co.uk or a Philips Microwave dealer.

You can order a new control unit (part number CPWBFB075MRU0 which comes with a display) from Encompass here.

Or you can get yours repaired for $39.95. Details here.

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That sounds like a problem on the invertor board. Unfortunately there is not a lot to be done on the board without a service manual and the needed experience.
Hope that helps.

easy to fix you need to cut the tracks to the led lights then solder 2 wires to the leds next use a 1k resistor on one of the wires then conect it straight to the power surply just after the bridge rectifier noteing+ and -

Give me the complete model # from the sticker inside the microwave so I can look into this for you.