My friend brought this 19" monitor around for me to have a look at.
The problem is with the top CCFL bulb, it is wearing out faster than the bottom. It exhibits the extended 2 seconds to black issue, usually takes 4~5 seconds before it cuts out. Picture on top half visibly flickers when this occurs.
I couldn't find a schematic of the particular power board but I did find one which used the same CCFL IC. (Attached.)
I located pin 14 of the IC as being the timer capacitor for the 2 secs cut off. I soldered a bridge across it -- this looks like an infinite capacitance to the timer circuit, so it never shuts off. The timer is almost always charged by a low current constant current source, so it's not a big deal to the IC if it's shorted out. It just never times out.
Result is, the top bulb flickers a few times when it tries to start, but then manages to work after about 30 seconds of flickering. Now, I have told friend that it's not a permanent fix, but even after the top bulb dies completely there will still be a bottom bulb and it will still be usable. He's looking for a new monitor now, but this'll do for the time being. Turning down the brightness makes it start quicker, and that worked for 18 months with my old 19" Xerox which had a dying backlight.
So, for a quick fix, consider disabling the timer.
The yellow wires are patching up some traces I previously cut when trying to disable the protection scheme. Doing that did keep the monitor on, but the bulbs flickered too much (continuously trying to auto-start), so I went for the timer disable method.
The problem is with the top CCFL bulb, it is wearing out faster than the bottom. It exhibits the extended 2 seconds to black issue, usually takes 4~5 seconds before it cuts out. Picture on top half visibly flickers when this occurs.
I couldn't find a schematic of the particular power board but I did find one which used the same CCFL IC. (Attached.)
I located pin 14 of the IC as being the timer capacitor for the 2 secs cut off. I soldered a bridge across it -- this looks like an infinite capacitance to the timer circuit, so it never shuts off. The timer is almost always charged by a low current constant current source, so it's not a big deal to the IC if it's shorted out. It just never times out.
Result is, the top bulb flickers a few times when it tries to start, but then manages to work after about 30 seconds of flickering. Now, I have told friend that it's not a permanent fix, but even after the top bulb dies completely there will still be a bottom bulb and it will still be usable. He's looking for a new monitor now, but this'll do for the time being. Turning down the brightness makes it start quicker, and that worked for 18 months with my old 19" Xerox which had a dying backlight.
So, for a quick fix, consider disabling the timer.
The yellow wires are patching up some traces I previously cut when trying to disable the protection scheme. Doing that did keep the monitor on, but the bulbs flickered too much (continuously trying to auto-start), so I went for the timer disable method.
Attached Files
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