Hello, i am working on a 15 inch color monitor. I have a 150W light
bulb connected and when i turn the monitor on, it starts to pulsate for
about 10 seconds at 2hz(+-)So it pulsates like 15 to 20 times and then
it stays at normal brightness. During all of this the monitor is NOT
connected to a PC, but when i do it statrs to pusate again but this
time indefenetly. I=B4ve tried changing the refresh rate and this causes
the pulses to speed up, so if i go from 800x600/50hz to 800x600/60hz,
the pulsating goes from about 1hz to 2hz and if I pull the VGA
connector the pulsating stops. Should i try a bigger light bulb?
I also get over 1000Vdc (DMM goes blank)both at the chopper
transistor=B4s and HOT=B4s drain pin. What controls B+ voltage? is it
just the HOT or is there a voltage regulator somewhere?
I am looking for a bad V regulatro or maybe a bad resistor somewhere,
Am I in the right direction here?
Thanks.

"onyxx" writes:

Hello, i am working on a 15 inch color monitor. I have a 150W light
bulb connected and when i turn the monitor on, it starts to pulsate for
about 10 seconds at 2hz(+-)So it pulsates like 15 to 20 times and then
it stays at normal brightness. During all of this the monitor is NOT
connected to a PC, but when i do it statrs to pusate again but this
time indefenetly. I´ve tried changing the refresh rate and this causes
the pulses to speed up, so if i go from 800x600/50hz to 800x600/60hz,
the pulsating goes from about 1hz to 2hz and if I pull the VGA
connector the pulsating stops. Should i try a bigger light bulb?
I also get over 1000Vdc (DMM goes blank)both at the chopper
transistor´s and HOT´s drain pin. What controls B+ voltage? is it
just the HOT or is there a voltage regulator somewhere?
I am looking for a bad V regulatro or maybe a bad resistor somewhere,
Am I in the right direction here?

What were the original symptoms?

100 W may be a bit low for a 15 inch monitor to come up properly with a
signal.

P.S. Don't put your poor DMM on those terminals! If it does come up
properly, the DMM may not survive.

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check the H-OUT transistor and any
caps in the power supply near hot spots
that may dry out the caps, disconnect the
h-out transistor before useing youre metre
to check the power supply, then use a light
bolb and connect it to ground and the collector
side of the h-out transistor on the board
with no transistor connected
it should be 120-150volts.

"onyxx" wrote in message
oups.com...
Hello, i am working on a 15 inch color monitor. I have a 150W light
bulb connected and when i turn the monitor on, it starts to pulsate for
about 10 seconds at 2hz(+-)So it pulsates like 15 to 20 times and then
it stays at normal brightness. During all of this the monitor is NOT
connected to a PC, but when i do it statrs to pusate again but this
time indefenetly. I´ve tried changing the refresh rate and this causes
the pulses to speed up, so if i go from 800x600/50hz to 800x600/60hz,
the pulsating goes from about 1hz to 2hz and if I pull the VGA
connector the pulsating stops. Should i try a bigger light bulb?
I also get over 1000Vdc (DMM goes blank)both at the chopper
transistor´s and HOT´s drain pin. What controls B+ voltage? is it
just the HOT or is there a voltage regulator somewhere?
I am looking for a bad V regulatro or maybe a bad resistor somewhere,
Am I in the right direction here?
Thanks.

Hi
are you using a scope, Digital or Analogue Meter?. There can be a difference
due to the waveform. I am not sure what to expect at flyback frequencies. I
am only happy when I get the same voltages as on the circuit diagram
(schematic)
Andy

"onyxx" wrote in message
oups.com...
Hello, i am working on a 15 inch color monitor. I have a 150W light
bulb connected and when i turn the monitor on, it starts to pulsate for
about 10 seconds at 2hz(+-)So it pulsates like 15 to 20 times and then
it stays at normal brightness. During all of this the monitor is NOT
connected to a PC, but when i do it statrs to pusate again but this
time indefenetly. I´ve tried changing the refresh rate and this causes
the pulses to speed up, so if i go from 800x600/50hz to 800x600/60hz,
the pulsating goes from about 1hz to 2hz and if I pull the VGA
connector the pulsating stops. Should i try a bigger light bulb?
I also get over 1000Vdc (DMM goes blank)both at the chopper
transistor´s and HOT´s drain pin. What controls B+ voltage? is it
just the HOT or is there a voltage regulator somewhere?
I am looking for a bad V regulatro or maybe a bad resistor somewhere,
Am I in the right direction here?
Thanks.

On 3 Oct 2005 12:09:16 -0700, "onyxx" wrote:

Hello, i am working on a 15 inch color monitor. I have a 150W light
bulb connected and when i turn the monitor on, it starts to pulsate for
about 10 seconds at 2hz(+-)So it pulsates like 15 to 20 times and then
it stays at normal brightness.

If it is at normal brightness...

During all of this the monitor is NOT
connected to a PC, but when i do it statrs to pusate again but this
time indefenetly. I´ve tried changing the refresh rate and this causes
the pulses to speed up, so if i go from 800x600/50hz to 800x600/60hz,
the pulsating goes from about 1hz to 2hz and if I pull the VGA
connector the pulsating stops. Should i try a bigger light bulb?
I also get over 1000Vdc (DMM goes blank)both at the chopper
transistor´s and HOT´s drain pin.

....it is no wonder that the DMM is complaining...if only I could
remember what "drain" means...FET terminal...equivalent to collector
or emmiter? Can't remember...if emitter, something weird is going on.
Hmmm.

Tom

What controls B+ voltage? is it
just the HOT or is there a voltage regulator somewhere?
I am looking for a bad V regulatro or maybe a bad resistor somewhere,
Am I in the right direction here?
Thanks.