CRT DISPLAYS ARE OBSOLETE, send them all to the recycle center  now.          

CRT means Cathode Ray TUBE Monitors,  ditch them, is best idea.   (we old folks call this "Hollow State Technology"  (it began really in 1897)
They lasted  for 110 years,  a good run ! for sure.

If you hit this below CRT  hard enough it IMPLODES. (below) Do not play inside as the 20,000 volts will not make your day. Not at all. ( Lethal)
If you have one 2 choices?
Read it carefully:  (learn  that nobody with smarts/savvy,  volunteers to take the 20kv hit grounded and through the chest. NOBODY.!  and few live to tell about it.

 If you put that energy trough your heart,  who knows what happens. As low as 10uA (micro amps) current can stop a heart and high voltage can puncture the skin and that is super dangerous.
That nerve on the heart? Don't play games with that body part, ever.!
If you do take  hit here, the pain is at grade 1000 out of 1000,  you will never forget it. (It can throw you across the room and get hurt real bad doing that too or hit others or cause huge cascaded damages...)

 The CRT is a large HV capacitor. (that holds charges for a very long time or seems near forever.) The glass is near a perfect insulator is why.!  Glass is !
If the OSD menu's button is dead, screen dead or dim (not turned down dim) or has funny coloring, retire it now. Buy a LCD flat screen monitor.
CRT's;   the CRT needs a trip to the  Recycle center  fast.
A working CRT is amazing today.
Most of the CRT's  are dead  today or the RED GUN is way low, (I can be raised higher in the Menu's of most OSD.)
 If the CRT fails , most parts are not found today... (good luck sourcing  relic legacy parts like this)
20" Monitor. below.
One of the more simple drawings, easy to understand.

The basic trouble shooting is the same as LCD display monitors.
If it will not power on its dead.
If the screen looks funny at 800x600 resolution this display is toast.
You can fiddle the knobs all day or the OSD but in the end it is toast.
If you see shadows in the  screen for white backgrounds thos burned phosphors in the face plate rear side (owner failed to use screen saver and did that)
Many of these cases have  secret key to open the case rear,  using  trip lever that fits inside a vent.  (all makers use there own tricks) this keeps from finding  dead kid with a screwdriver in the hand.

version 1.  12-9-2017