Viewsonic P775 no horiz deflection, Hv preasent

M

Mike

Guest
I have this monitor, and the flyback "hiccup pulses" and there is no
horizontal deflection on the screen, just a line from top to bottom.

This set has HV10 chassis, and its the set that has 2 HOTs.

one provides the flyback drive, and the other drives the yoke.

The guy that gave it to me said that it just collapsed to a line, started
pulsing, and he smelled smoke.

I powered it up, never saw smoke, but the heatsink that drives the yoke got
quite hot after about a minute of operation. I pulled out the HOT for the
yoke, it is shorted, Damper OK.

im thinking bad yoke, so I replaced the HOT, and damper to be safe, and
tried another yoke, the set poweres up, and I hear a heavy ring from the
flyback insted of pulses, and the horiz sweep is now restored, but is
insufficiant, and it slowly widens, and is properly synchronized, there is
all kinds of noise in the picture, and i hear the noise in the flyback, and
the HOT begins to get red hot, and smoke.

so, I pulled the yoke, and no change, when you first turn it on, the flyback
makes a loud ring, the sweep begins to get wider, with foldover, noise,
bars, everything. and the noisy ring begins to settle to a normal ring, but
when it does, thats when the new HOT begins to smoke.

The flyback HOT stays normal, but the yoke HOT gets hot and smokes with the
noisy ring settling. The sweep never fills the raster, and I pull the plug
immediatly, to avoid damage to the new HOT.

pulling the yoke makes no difference.
Any ideas? im assuming something is loading down the yoke HOT, but the
collector only connects to the yoke, so without the yoke, it shouldnt get
hot, it should run normal, but it still does the same thing, so Im thinking
the B+ on the yoke HOT is way over the raitings, but it would affect the
flyback HOT wouldnt it? the flyback HOT runs happily, and heatsink stays
reletivly cool

Im stumped, any Ideas?
 
I forgot to mention, that this problem is VERY COMMON when switching modes,
especially in linux.

and im attempting to repair mine. so far, I think its a B+ problem, or a
problem in that scan circuit.





"Mike" <mbates14@fuse.net> wrote in message
news:MkjXa.38741$hc.32946@fe3.columbus.rr.com...
I have this monitor, and the flyback "hiccup pulses" and there is no
horizontal deflection on the screen, just a line from top to bottom.

This set has HV10 chassis, and its the set that has 2 HOTs.

one provides the flyback drive, and the other drives the yoke.

The guy that gave it to me said that it just collapsed to a line, started
pulsing, and he smelled smoke.

I powered it up, never saw smoke, but the heatsink that drives the yoke
got
quite hot after about a minute of operation. I pulled out the HOT for the
yoke, it is shorted, Damper OK.

im thinking bad yoke, so I replaced the HOT, and damper to be safe, and
tried another yoke, the set poweres up, and I hear a heavy ring from the
flyback insted of pulses, and the horiz sweep is now restored, but is
insufficiant, and it slowly widens, and is properly synchronized, there is
all kinds of noise in the picture, and i hear the noise in the flyback,
and
the HOT begins to get red hot, and smoke.

so, I pulled the yoke, and no change, when you first turn it on, the
flyback
makes a loud ring, the sweep begins to get wider, with foldover, noise,
bars, everything. and the noisy ring begins to settle to a normal ring,
but
when it does, thats when the new HOT begins to smoke.

The flyback HOT stays normal, but the yoke HOT gets hot and smokes with
the
noisy ring settling. The sweep never fills the raster, and I pull the plug
immediatly, to avoid damage to the new HOT.

pulling the yoke makes no difference.
Any ideas? im assuming something is loading down the yoke HOT, but the
collector only connects to the yoke, so without the yoke, it shouldnt get
hot, it should run normal, but it still does the same thing, so Im
thinking
the B+ on the yoke HOT is way over the raitings, but it would affect the
flyback HOT wouldnt it? the flyback HOT runs happily, and heatsink stays
reletivly cool

Im stumped, any Ideas?
Click to expand...
 
normal 1024x768 in XP

75hz, its dead now. I have to find out what is causeing the transistor to
burn up now.

it keeps overheating and shorting in under a few seconds. even in 640x480,
so, when the transistor shorted the first time, it killed something in
series with it somewhere. that wants to take it back out. and it did.




"Dave D" <someone@somewhere.com> wrote in message
news:bglsgj$sje$1@hercules.btinternet.com...
"Mike" <mbates14@fuse.net> wrote in message
news:CHjXa.38951$hc.35865@fe3.columbus.rr.com...
I forgot to mention, that this problem is VERY COMMON when switching
modes,
especially in linux.

and im attempting to repair mine. so far, I think its a B+ problem, or a
problem in that scan circuit.


Is the monitor being run at an acceptable refresh rate? It sounds like too
high a scan rate is being forced. Does this happen in text mode or only in
graphical mode?

Dave
Click to expand...
 
"Mike" <mbates14@fuse.net> wrote in message
news:CHjXa.38951$hc.35865@fe3.columbus.rr.com...
I forgot to mention, that this problem is VERY COMMON when switching
modes,
especially in linux.

and im attempting to repair mine. so far, I think its a B+ problem, or a
problem in that scan circuit.
Click to expand...
Is the monitor being run at an acceptable refresh rate? It sounds like too
high a scan rate is being forced. Does this happen in text mode or only in
graphical mode?

Dave
 
The HV10 sounds like one of those that was made by Panasonic for Viewsonic.
Did you check the FET and electrolytic capacitor that act as a voltage
regulator for the Horizontal sweep transistor (HOT) ?
Often, a shorted FET or bad capacitor will cause the HOT to blow.

The probably of the yoke going bad is very, very low. I have been
repairing monitors for over 8 years and have yet to come across a
defective yoke. If you do change the yoke, you have to get one that
is fairly close to the same impedence as the original, especially
one the horizontal winding. Use an inductance meter to match yokes.
It is very difficult to do a real good job in converging the set after
replacing the yoke. I generally replace the picture tube and yoke as
a unit, so that I do not have to re-converge the colors.
John
 
probably right.

the only fet I know is the one in the chopper supply.

The yoke isnt bad, I just subbed it to see if it were causing the problem,
and it didnt, I even pulled the yoke plug, and it still did the same thing,
the transistor will get red hot and short, I can see that the width of the
deflection is trying to fill the raster, but its got noise in the picture,
foldover, piecrusting, bars, everything. then it will collaps and short the
HOT, but the flyback will still run, as it is powered off of another HOT.
but all you will see is just a line pulsing and running up and down the
screen.


"John Gill" <jdgill@juno.com> wrote in message
news:71016e83.0308040948.9817d@posting.google.com...
The HV10 sounds like one of those that was made by Panasonic for
Viewsonic.
Did you check the FET and electrolytic capacitor that act as a voltage
regulator for the Horizontal sweep transistor (HOT) ?
Often, a shorted FET or bad capacitor will cause the HOT to blow.

The probably of the yoke going bad is very, very low. I have been
repairing monitors for over 8 years and have yet to come across a
defective yoke. If you do change the yoke, you have to get one that
is fairly close to the same impedence as the original, especially
one the horizontal winding. Use an inductance meter to match yokes.
It is very difficult to do a real good job in converging the set after
replacing the yoke. I generally replace the picture tube and yoke as
a unit, so that I do not have to re-converge the colors.
John
Click to expand...
 
there is a big heatsink next to the yoke winding, has 3 devices mounted on
it.

It has the sweep output HOT, the damper to it, and another little
transistor, but not sure what its for.





"John Gill" <jdgill@juno.com> wrote in message
news:71016e83.0308040948.9817d@posting.google.com...
The HV10 sounds like one of those that was made by Panasonic for
Viewsonic.
Did you check the FET and electrolytic capacitor that act as a voltage
regulator for the Horizontal sweep transistor (HOT) ?
Often, a shorted FET or bad capacitor will cause the HOT to blow.

The probably of the yoke going bad is very, very low. I have been
repairing monitors for over 8 years and have yet to come across a
defective yoke. If you do change the yoke, you have to get one that
is fairly close to the same impedence as the original, especially
one the horizontal winding. Use an inductance meter to match yokes.
It is very difficult to do a real good job in converging the set after
replacing the yoke. I generally replace the picture tube and yoke as
a unit, so that I do not have to re-converge the colors.
John
Click to expand...
 
man, after closely examining the set, there are millons of bad solder
joints, with a small ring crack.

one of these are noisy somewhere.

I bet my bottom dollar that is where my problem lies





"Mike" <mbates14@fuse.net> wrote in message
news:MkjXa.38741$hc.32946@fe3.columbus.rr.com...
I have this monitor, and the flyback "hiccup pulses" and there is no
horizontal deflection on the screen, just a line from top to bottom.

This set has HV10 chassis, and its the set that has 2 HOTs.

one provides the flyback drive, and the other drives the yoke.

The guy that gave it to me said that it just collapsed to a line, started
pulsing, and he smelled smoke.

I powered it up, never saw smoke, but the heatsink that drives the yoke
got
quite hot after about a minute of operation. I pulled out the HOT for the
yoke, it is shorted, Damper OK.

im thinking bad yoke, so I replaced the HOT, and damper to be safe, and
tried another yoke, the set poweres up, and I hear a heavy ring from the
flyback insted of pulses, and the horiz sweep is now restored, but is
insufficiant, and it slowly widens, and is properly synchronized, there is
all kinds of noise in the picture, and i hear the noise in the flyback,
and
the HOT begins to get red hot, and smoke.

so, I pulled the yoke, and no change, when you first turn it on, the
flyback
makes a loud ring, the sweep begins to get wider, with foldover, noise,
bars, everything. and the noisy ring begins to settle to a normal ring,
but
when it does, thats when the new HOT begins to smoke.

The flyback HOT stays normal, but the yoke HOT gets hot and smokes with
the
noisy ring settling. The sweep never fills the raster, and I pull the plug
immediatly, to avoid damage to the new HOT.

pulling the yoke makes no difference.
Any ideas? im assuming something is loading down the yoke HOT, but the
collector only connects to the yoke, so without the yoke, it shouldnt get
hot, it should run normal, but it still does the same thing, so Im
thinking
the B+ on the yoke HOT is way over the raitings, but it would affect the
flyback HOT wouldnt it? the flyback HOT runs happily, and heatsink stays
reletivly cool

Im stumped, any Ideas?
Click to expand...
 
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