Can't What displayed error message means

This is why doing Firmware Upgrades is so risky. The firmware tells the printer what to do when it switches on before self testing and loading software. If the Firmware is corrupt, the printer becomes a giant paperweight. Help here

Solved: HP 1536DNF Firmware Corrupt Ready 2 Download

HP Support Community https://h30434.www3.hp.com > LaserJet-Printing > td-p Jun 4, 2020 - Solved: Hi, My HP Laserjet 1536dnf multifunction printer shows the 'Firmware Corrupt Ready 2 Download' message. I have read few treads in the forum, - 7633086.

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50.3 means the fuser is getting too hot. It will either be a problem with the thermistor in the fuser or the power supply. If you can find a another fuser to test with you can answer the question pretty quickly.

I'm not familiar with this model but have you ran the cleaning mode if it has one?

I've seen this exact error a few times on the 4101s & turned out to be a bad EIO hard drive.If you replace the drive, you'll most likely have to download the newest firmware & load it to get every feature back.
You can try & initialize the drive first though:
- Turn off printer
- Press & hold [Start] button
- Turn printer on, wait for all 3 LEDs to stay solid then release button
- Press & release [Left] arrow button (should read "Initialize Disks" on display
- Press & release [Select], then wait for printer to warm up
Listen also to the drive & if you hear it clicking over & over then it's bad & will need replaced.

Replace the fuser

This means that the printer cannot read the E-Label on the cartridge, or it is not properly installed.

1. Reinstalle the cartridge
2. Power cycle the device
3. If the problem is not solved, replace the cartridge. (Is the cartridge a remanufactured one? this can be a problem)
4. Check if correct cartridge type.

FROM THE SERVICE MANUAL
W2 INVALID PERS:
The job was not printed because the requested personality,
such as PostScript, was not installed. Install the language in
which the files are sent, together with enough memory to
support that language.
I SUGGEST CHECK IF YOU GOT THE POSTSCRIPT INSTALLED

If you keep getting 80 service, first recycle the power to the printer (try a few times if the error doesn't go). If that doesn't work replace the MIO card (the bit the network cable goes in)

Try the following steps to reinitialize the HDD:

1 Turn the printer off.
2 Turn the printer on.
3 Press and hold PAUSE/RESUME (LJ 9500) or START (LJ 9500mfp) on the control panel during the
memory count.
4 Hold PAUSE/RESUME (LJ 9500) or START (LJ 9500mfp) down until all three error lights illuminate
steadily.
5 Press (the 5 button on the MFP) until INITIALIZE DISKS appears on the display panel.
6 Press (the 6 button on the MFP).
7 The printer begins initializing the disk (this might take a moment). The control panel displays the
HP event logo and eventually displays READY.

This is normally down to the information or data if you will that you have sent to the printer. Delete all in the print que and restart the printer.

If this doesn't work then tun the printer of and remove the additional memory. Turn on and tested again.

If still doesn't work then problem is with the printer formatter board the firmware is corrupted or the board is faulty either one is a hp repair or a second hand machine.

I do hope the first two help you
Thanks J