KDS VS195 19" Monitor blury, dim, then off

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Hi everyone,

I've got a KDS VS195 monitor (FCCID EVOKD-1900) that's been working
great for years. The picture has been getting darker and more
recently out of focus (then BADLY out of focus).

Yesterday, the brightness level dropped to almost nothing within 30
seconds. As this was happening, the picture also was going out of
focus.

As the brigtness goes down and picture out of focus, the size of the
picture does not change, so the deflection circuits and voltages seem
ok.

I don't have a schematic, but from the block diagram, it says "Double
Focus" on the flyback, and there's also a "Hor Ver Dynamic Focus"
circuit.

The video circuitry appears to be working as I have a KVM switch and
you can hear the monitor go into standby if the 2nd PC is off.
Likewise, you can hear it come out of standby when switching over to
the main PC. Interesting note here, you can hear the static build up
on the monitor as it's coming out of standby, but it does sound
"softter" than normal.

The catch is I've been googling tonight for four hours or so on this
monitor and it's behaving perfectly! Go figure.

I've read through the prior posts on sci.electronics.repari, as well
as a repair forum or two, but none of the previous problems matched
mine.

Sorry so long winded, but I wanted to be sure to include as much
information as possible.

Thanks in advance!

-Frank
Holland, PA

 

[[email protected]]

Hi everyone,

I've got a KDS VS195 monitor (FCCID EVOKD-1900) that's been working
great for years. The picture has been getting darker and more
recently out of focus (then BADLY out of focus).

Yesterday, the brightness level dropped to almost nothing within 30
seconds. As this was happening, the picture also was going out of
focus.

As the brigtness goes down and picture out of focus, the size of the
picture does not change, so the deflection circuits and voltages seem
ok.

I don't have a schematic, but from the block diagram, it says "Double
Focus" on the flyback, and there's also a "Hor Ver Dynamic Focus"
circuit.

The video circuitry appears to be working as I have a KVM switch and
you can hear the monitor go into standby if the 2nd PC is off.
Likewise, you can hear it come out of standby when switching over to
the main PC. Interesting note here, you can hear the static build up
on the monitor as it's coming out of standby, but it does sound
"softter" than normal.

The catch is I've been googling tonight for four hours or so on this
monitor and it's behaving perfectly! Go figure.

I've read through the prior posts on sci.electronics.repari, as well
as a repair forum or two, but none of the previous problems matched
mine.

Sorry so long winded, but I wanted to be sure to include as much
information as possible.

Thanks in advance!

-Frank
Holland, PA

As the brigtness goes down and picture out of focus, the size of the
picture does not change, so the deflection circuits and voltages seem
ok.

I would not go with that conclusion. Deflection angle depends on final
anode V and deflection V, and if both go up or down together the
deflection angle stays constant. This enabled tvs to run quite well
with unstabilised psus for decades. Early Philips dropper smpsus in
particular were all over the place voltage wise, but the pic stayed
steady.

As a first guess I'd say maybe theres a short on the focus V, causing
some defocussing and loading the psu excessively. As this short
worsens, psu Vout drops, causing falling tube output along with the
worsening focus.


NT