LCD Monitor Service/Factory Menus

I’m not sure many people know, but the chips inside LCD monitors are actually fairly smart. For one thing, they generate the on-screen overlay displays which you set your settings with, and they do scaling of different resolutions to your panel (except for those bottom end Yamakasi monitors sans scaler). They also digitize VGA (analog) inputs, and often talk multiple digital inputs too (say DVI and DisplayPort). They’re in charge of sleep, wakeup and controlling backlight brightnesses.

What you don’t normally see is the service menu. This is also known as a factory menu which is strictly “for technicians only”. Access to this menu is by (sometimes) undocumented means involving combinations of unlikely inputs to the buttons.

Inside the service menu, you might find several handy things (or none at all, depending on monitor):

  • Backlight-on time: this is a count of how long the screen is actually lit up with the backlight. Primarily of importance for CCFL backlit (i.e. non LED) screens as their lifetimes often measure around 50,000 hours. Gives you an indication of how much the screen is actually used (but beware of rollover – some monitors seem to roll-over at small values).
  • Power-on time: this is a count of how long the power was “on” to the monitor – including time in standby. This gives you a way to calculate the “duty cycle” of the screen – i.e. time used vs time plugged in.
  • Power-cycles: lets you know how many times it’s turned on and off – also important as CCFL backlight tubes suffer from electrode sputtering at each cycle – short numerous cycles can kill tubes before they reach their 50,000 hour rated lifetime.
  • Burn-in test mode: this is normally a mode used for factory testing which cycles between solid colour screens at specific intervals for inspection purposes.
  • Panel ID: can let you know who made the panel – e.g. CMO for Chi-Mei Optics, AUO for AU Optoelectronics, CPT for Chunghwa Picture Tubes and other codes for Samsung, LG (which covers most displays).
  • Scaler ID: lets you know what chip is being used for the scaler. Is often a codename or a part-number.
  • Channel Bias: displays and or alters factory calibrated values for offsets for the RGB channels to match the driver to the LCD panel.
  • Register manipulation: DANGER! This lets you talk to the registers of the scaler/driver chips directly – modifying these values can kill your screen.
  • Panel Channel: DANGER! Don’t touch this – I’m not sure what it does, but from the sounds of it, you could lose your LCD connection to your scaler/driver and not see anything (and thusly cannot recover)!
  • ISP: In-system programming (possibly by using DVI or VGA and flashing patterns of data as coloured/black and white boxes) – not unheard of in a few cases, but don’t touch this either unless you want to potentially brick a monitor.
  • Mode Locks: Some menus allow you to lock the panel mode, so it won’t autodetect the input. Some danger here, you could lock your monitor in a mode which you cannot generate and display – thus making your monitor unusable.
  • Firmware revision: not very useful, but it’s a number.
  • Mode switches: some monitors allow you to change features (overdrive), or adjust HDCP modes from within the service menu (to improve compatibility).
  • Resets: allow you to clear all monitor data – this is not safe to use as it may clear factory calibrated data (unlike the “regular menu” factory defaults reset). Be careful – you’re in a service menu, not a user menu!

Of course, this is not in the user manual – but it is in difficult-to-obtain service manuals. Really, you shouldn’t poke around with the values if you don’t know what they do – whatever you do – don’t poke around with the bias or register values. If you harm your equipment, that’s your own fault – I’m not responsible for what you do! But looking is generally harmless.

Ways to access the service/factory menus for the monitors I am using are as follows:

Dell E248WFP

Hold Menu, + and Power at the same time when powering on. Open menu, navigate to factory reset sub-menu, then navigate to F icon in bottom right corner and select. Credit goes to Josh Street.

BenQ FP222W

Hold Menu + Enter + Power until green LED comes on, then press the ‘i’ button to bring up service menu. Discovered this one by random button combination pushing.

BenQ G2000W

Hold Menu and Power when turning on, then press menu to bring up the factory menu. Discovered this by chance.

Asus VW161D

Power on, press menu and hold. Unplug power till monitor goes off, and then plug monitor back in. Navigate to the F icon in top left corner, and press the [menu] button for Enter. Credit goes to this service manual for a different Asus monitor (which also suggests that Asus monitors are made by AOC!) Beware, accessing factory menu on this monitor appears to reset all your preferences – so do write them down first!

To Conclude …

Exiting the service menu is often just as simple as turning the monitor off, and then on again. Voila.

If you can’t find the method to get in through an online search (even for other models of the same monitor), try pressing combinations of button + power, and then menu or other buttons. You might stumble upon it, but it will be of limited utility. One use can be checking out the power on hours for a second hand monitor – but be aware that some models (all non BenQ ones I have) seem to have low rollover values (probably in the 512/1024/2048/4096/8192 hour region) which might not capture the complete backlight on time. Worse is that on Dell monitors, you can be tricky and “reset” the backlight on time. So I guess it’s cool, but not entirely of much utility.

About lui_gough

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8 Responses to LCD Monitor Service/Factory Menus

  1. Roberto says:

    What can do the command offset and gain?
    I have an asus pa248q here is my factory menu: https://dl.dropboxusercontent.com/u/53483129/20131017_112742.jpg

    I also try to move this two command, but i can’t see any difference in brightness or contrast

    • lui_gough says:

      Dear Roberto,

      I’m afraid that the uses of these parameters will only be known for sure by the engineers that designed the system. You may not see a difference because this parameter may only have meaning in certain designs of scaler board, or in certain configurations (e.g. using analog VGA, getting video from a second scaler chip on the PCB). Maybe it’s mislabelled, and new scaler chips do not support this register value, or maybe it is making subtle drive level differences to the LCD that are hard to notice (e.g. black levels, balance). Whatever it is, you play with them at your own risk!

      – Gough

  2. Leon says:

    Hi, i have a ASUS VX239H, to access this service menu you must turn off the monitor and then turn on while you are pressing MENU, then release all, and on the MENU OSD that appears on top lef, you must scroll down to the letter F and hit MENU.

    The thig is that i dont know if its safe to do a Reset from that service menu, i have a issue with a HDMI port and i think its probably can fixed by doing the reset, but i not want to do unless im sure that the monitor all other software will be ok and exactly like now, what do you think?, Thanks.

    • lui_gough says:

      Factory menus are for factory use. Do whatever you want at your own risk as some of the settings will destroy or otherwise render your monitor permanently damaged. I would not play with it unless I was willing to sacrifice the monitor – and it’s unlikely that it would solve your problem anyway. Don’t do things because you think it will solve your problem. Only do things when you know that it will solve your problem or otherwise you might find yourself in the middle of a costly mistake.

      – Gough

      • Leon says:

        Yes, thats why i say “unless im sure that the monitor all other software will be ok and exactly like now”, jajaja, i contact ASUS too, so i just want to know if perhaps someone else have tryed this before, tahnks anyway.

  3. Dave W says:

    Thank you so much, the purple splash screen that came installed on my monitor blinded me with brightness every time I started the PC, with the info from your site I was able to enter the factory menu and turn it off.

  4. Aderito Loureiro says:

    Got an error on my Asus all in one Et2400. Somehow got in factory menu, but cannot get out! Help Please ! It keeps changing setting without me touching nothing. How can i exit?

    • lui_gough says:

      It would appear you may have a “stuck button” on your front panel, which is why it’s inadvertently causing the factory-mode menu to appear when pressed with the power button. I don’t think you will be successful in exiting the factory menu in this case. Normally the factory menu appears but can be exited by regular pushes of the front panel buttons or by rebooting the monitor. It is normally not persistent.

      Unless you can unstick the button (try pressing all buttons, giving them a wiggle or a clean), it could be a faulty switch with stuck contacts that can only be fixed either by returning the monitor to have the front panel button assembly replaced, or by opening it up and doing the replacement yourself with a soldering iron.

      That being said, I have experienced monitors with “stuck button” syndrome that had other faults which caused it to appear as if it had a stuck button – things like bad capacitors in the power supply board on the monitor could also cause this.

      Other than this, maybe some random change has reconfigured your monitor for permanent testing mode, in which case, there isn’t really anything you can do about it as most settings are undocumented.

      – Gough

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