Dead Sony 300sf monitor

My Sony Multiscan 300sf monitor suddenly died on my about 4 days ago. The only cause I can think of is out-of-range signals, as this happened while booting up a new Linux distro and specifying custom screen resolution. The screen just quietly went black. So, I cycled the power on and off a couple of times hoping to restore normal operation, but no luck.

When the unit was working properly, pressing the power button would produce a rather loud "thunk" sound, like a heavy-duty relay being engaged. This would be followed by a softer click, and then the video would come on.

Now, when I press the power button, nothing happens: the screen remains black and there is absolutely no sound coming from it. Following some threads I found on Google, I tried holding the -> button in. After a couple of seconds I get the familiar clicks, a loud one followed by a soft one. While this is happening, the "Power" and "Power Saving" LEDs go through a flashing sequence which ends with both LEDs blinking in unisson,

1/2 second on and 1/2 second off, forever. No activity on the screen itself.

I've tried pressing the "RESET" button as well as disconnecting the power cord and the VGA cable to no avail.

Any ideas or suggestions would be greatly appreciated.

Max

The thunk/hum sound is the degaussing coil energizing; the softer click is the coil's relay disengaging (i.e., coil switched off). The degauss coil is wrapped around the CRT face perimeter, and it's switched on with each power up to help remove minor color impurities in the screen. Most newer monitors have a manual degauss function, with which you can see the effect the coil has on the screen while there's video present -- it's rather dramatic in most cases.

A likely culprit is in the B+ supply -- it powers the flyback xformer, which in turn develops the high CRT screen (anode) voltage, which in turns pulls the electron beam to the phosphor screen. An oversimplification, but a quick Google search will get you tons of info on the subject. You've probably got one or more bad horizontal output transistors, plus another support component or three. Multisync monitors can have several H-OUT xistors for the various sync frequencies used in the various graphics modes. Since you believe you stressed the monitor out of its design limits, this further leads me to suspect the H-OUT(s).

Designers frequently seem to protect a 10-cent fuse by having the more costly components blow instead. Even in the unlikely event that replacing a fuse "fixes" the problem, one should keep in mind that _something_ caused that fuse to blow, and unless the affected components are replaced, the unit is destined to have a subsequent and premature failure.

This is definitely not a DIY repair for the uninitiated. There are many areas of lethal potential inside a CRT monitor, even after the unit has been powered down for some time.