CRT monitor Help

[jleaman]

Is there any one here on the form that is good at working on crt monit0r's.

I was given a dell 21" monitor it works great but the coloor is off. this only happens 5 minits after turn on. It has a Nice sony trinitron tube in it Really fine pitch and a great monitor .. i dont want to throw it away.. any one guide me in the right direction.

I have done a solder job on the board that is connected to the tube back and the neck.. Pictures are available also..

 

[jleaman]

ok this has to be a cap.. because if i turn it off for a min then turn it right back on.. it works for about another min then goes yellow ish.. again..


Any ideas where to start looking ? to replace cap's..

 

[Frank Berry]

I suspect that the CRT has developed a grid to cathode short in the green gun.
It's a known problem with some Sony CRT's.
We have the same problem with some of our Sony video monitors at FOX.

 

[jleaman]

is it easy to fix or to much.. ?

It is a sweet monitor im on it right now and seriousely want to buy 2 more so i can run dual monitors with it.. i like them alot...


Any way to fix it.. ?

 

[Frank Berry]

While the monitor is on, tap on the neck of the tube.
Do you see anything happening on the screen (changes in color, horizontal lines)?

If the answer is yes, please e-mail me directly and I'll give you some information about clearing the short.

If the answer is no, Last Rites are in order for the monitor.

 

[jleaman]

how hard do you want me to tap on this tube neck.. where should i be tapping.. what should i be looking for.. remember this occurs when the monitor is on after 2 min or more.. the first 2 min it is ok.. but aftetr that it goes yellow ish..


sniff..

 

[Frank Berry]

Use your finger and tap on the neck directly over the electron guns. You can even tap using the wooden handle of a small knife.
The reason for tapping is to see if the short between the grid (G1) and the cathode is caused by a tiny bit of material that has fallen from the cathode and is wedged between the cathode and the control grid.
When tapping, please look for any changes on the CRT screen.
Tell me what you see.

 

[jleaman]

hah im not using my finger.. NOT!!


ok i did what you said.. didnt see any changes at all..

a friend was saying that tehre might be a short in one of the transisters BUT what one could be the problem..

 

[Frank Berry]

If the monitor looks good for the first couple of minutes and then goes "yellowish," the problem is most certainly the CRT.

Something in the tube is shorting when the filament brings the cathode up to operating temperature.

 

[jleaman]

so the cure for this is to shake it lot's : O) or bang the tube neck so the shorting object drops or loosens up.. ?

 

[TonyTecson]

how old is your monitor?

i agree with frank, sometimes tapping on the side of the casing can bring the same result, have you tried wiggling on the cable end that connects to the pc? if the picture becomes normal, then you may have intermittent cable. make sure you clean the crt board very well after doing soldering to find out which points you might have missed, lacquer thinner and a tootbrush would do fine...

 

[Frank Berry]

Can you determine which wires provide the R, G and B (red, green and blue) drive to the CRT board?
If you can do this, I suggest that you swap B wire with the G wire as a test.
After doing this, the CRT will not have the correct colors.
Wait five minutes.
If the screen turns yellowish, it's the tube.
If the screen turns magenta, it's not the tube. It's something else.