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