Monitor dying or is it dead ?

[format c:]

HI there, I think my AOC 9G1R monitor has just died
this is a 19 inch unit and it is about 3.5 years old and resides on my workbench where I test and rebuild computers
During a hard drive test the screen went translucent green with semi horozonatal green lines running across the display
I turn the monitor off and on with no results, I disconnected it from my KVM switch and turned the monitor on while it was disconnected and I got that same ugly green screen
Then I connected the same monitor directly to the system I was testing and got the same green screen of death
I slapped the monitor on the right side and got it back a couple of times for only a half second, Almost like something is loose inside
Any opinions? I have the feeling she goes to the recycling depot along with a dead IBM, A loud popping banging 21 incher, Hmm Pop Bang green
Any idea would be appreciated, Looks like I am on the hunt for a monitor

[Platypus]

The green cast and zig-zag lines (sounds like "retrace lines") probably indicate either solder joint(s) gone bad (commonly on the CRT baseboard), or an internal short in the green gun in the CRT itself. The latter can be considered terminal.

Do you have anyone with the capacity to solder over the circuit board(s) for bad joints and see if that cures it?

[confus-ed]

..Do you have anyone with the capacity to solder over the circuit board..

Is there a joke in there somewhere's about electrical safety ? If there isn't I might charge for one before somebody gets shocked by the potential capacity that might be lurking (in the monitor !)

Safety Guidelines for High Voltage and/or Line Powered Equipment

[Platypus]

No resistance to doing repairs at ohm? How farad some people go?

Do you have anyone with the capacity to solder over the circuit board...?

If they don't understand electrical safety, the answer to the above question would be No...

There's another bad pun there too

can be considered terminal

[format c:]

I know some one that can solder ICs on PCBs, I know the risk when opening up a monitor case
Could be fatal with all that stored voltage in the yoke, I may carefully check it out and I mean carefully
Looka like I am shopping for a monitor

[format c:]

Just to let you all know, That monitor works fine after sitting over night, I wonder if something is getting warm and failing, Could be bad solder like some one suggested

[Platypus]

The cause can certainly be temperature sensitive, whether within the CRT gun assembly, bad solder joints or a temperature sensitive component (eg video transistor). Mention of striking the monitor briefly curing it suggests it is also partially mechanical, so solder joints or shorting in the CRT both seem possible. Soldering over the CRT baseboard, or Neck Board, is a good start to eliminate the joints as a cause. Depending on the design, some componentry on the main board could be involved too. Unfortunately the Neck Board usually has awkward shielding, like in the illustration below.

The yoke itself is not a stored voltage hazard when the monitor is not operating, although it has hazardous voltages on its terminals when operating.

The main culprit for remaining charged for considerable periods after shutdown is the connector (Ultor cap) delivering the High Voltage to the CRT. Although other capacitors can also be charged to reasonably high voltages, they normally discharge quite quickly.



There is a lot of information on the site of the above image:

http://repairfaq.ece.drexel.edu/sam/monfaq.htm

[CeeBee]

Zig-zag lines & a bright milky screen -> look for a potentiometer in the high voltage area - near the "transformer" that has a big thick wire going to the CRT.
There should be 2 or 3 such potentiometers in the area. One of them controls the cutting point (black level) - that is the one you are looking for, in many cases there is just a bad contact there - slightly turn it left or right. If there are 2, the other is for focus. If there are 3, one is for focus and one is for brightness in most cases. Sometimes this potentiometer is placed in a module attached to the end of the CRT. Make sure you use a well-insulated screwdriver and try not to get close to the HV cable - common voltages are 20-30kV. If you don't know what you are doing, then don't do it, it's not worth risking your life.
BTW, it could very well be another component in the blanking circuit.

[Platypus]

a bright milky screen

Normally, as you say, you'd expect white overdrive and retrace lines from incorrect Screen bias.

Since the cast and retrace are green, it's reasonable to expect the fault is likely in the green drive rather than the G2.

[CeeBee]

Not necesarily (although possible), since the guns have different gains and cutoff points. If the green is almost a pure green, then yes, it's the green drive. Otherwise it could even be a focus-G2 short inside the CRT

[Platypus]

Not necesarily (although possible), since the guns have different gains and cutoff points.

True, hence my vote of "likely" for green drive, rather than "certain".

it could even be a focus-G2 short inside the CRT

Yes, the screen brightness will vary if you adjust the focus potentiometer.

Judicious tapping of the CRT neck can reveal much...

[slgrieb]

Yes, your monitor is dead, but why stress over it? Don't you have spares on hand? I can buy OK used monitors for $30-$50 bucks, so I always have some on hand. I just don't like KVM switches as a solution for testing multiple systems. As I have said before, I'd rather spend the few bucks to have several monitors, mice, and keyboards attached to individual systems than put all my eggs in one basket. I like the concept of defense in depth.

[format c:]

One problem Is room on the bench, and of course money, I will be looking for a good deal on a decent work monitor
For now it seeams to work, I have only had the monitor on for a short time. When it failed it had been on for a while
I thank everyone for their input on this matter