Hi,

I'm working on a monitor for a friend of mine, she said that it smelled
like burning plastic for three days before it went bad.

The monitor:
"Proview model: 786N"
"Product no: PS720F-1s"
"Product series: DZ-777NS"

When you first turn it in the relays click like they are supposed to,
after a moment or two the little "Check signal" window pops up, but it
is scrunched on the left side and spread way apart on the right side.
The screen looks normal otherwise.

At least this is what I thought until I opened the case the turned the
brightness up, the vertical appears to be fine, but the horizontal stops
about three inches from both sides of the screen.

My first thought in this is that the horizontal section is not getting
enough voltage, if I turn the brightness all the way up the picture
shrinks inward even more (although it does get brighter). I posted a
picture online if you want to look at this:
http://home.comcast.net/~lj_robins/badmonitor/

One other thing is that the buttons on the front will not active the
geometric adjustment menus but they will bring it out of "sleep" mode.

Nothing appears to be burnt of fried on either side of the circuit
board, I'm not sure where to start with this thing, any suggestions?


-Landon

"lj_robins" wrote in message
. ..

When you first turn it in the relays click like they are supposed to,
after a moment or two the little "Check signal" window pops up, but it is
scrunched on the left side and spread way apart on the right side. The
screen looks normal otherwise.

Shorted turn in the yoke?

Homer J Simpson wrote:
"lj_robins" wrote in message
. ..

When you first turn it in the relays click like they are supposed to,
after a moment or two the little "Check signal" window pops up, but it is
scrunched on the left side and spread way apart on the right side. The
screen looks normal otherwise.

Shorted turn in the yoke?












Hi, thanks for replying.

I pulled the 4-pin connector off the circuit board, the Blue and Red
wires make one loop, they are reading 0.7 ohms, the Yellow and Brown
wires make the second loop, they reading 7.6 ohms.

I'm assuming and the 0.7 ohms on the red and blue wires is not normal.
All four wires feed into a closed module sitting on top of the neck of
the CRT. I'm going to open this (if possible without destroying it) and
see if the source of the burning smell was coming from inside it.

The bottom of it's circuit board is visible, there are schematic symbols
of resistors, etc. silk screened onto it.

More later...


-Landon

A 1.5 MB pic. Brilliant.
JR

lj_robins wrote:

Hi,

I'm working on a monitor for a friend of mine, she said that it smelled
like burning plastic for three days before it went bad.

The monitor:
"Proview model: 786N"
"Product no: PS720F-1s"
"Product series: DZ-777NS"

When you first turn it in the relays click like they are supposed to,
after a moment or two the little "Check signal" window pops up, but it
is scrunched on the left side and spread way apart on the right side.
The screen looks normal otherwise.

At least this is what I thought until I opened the case the turned the
brightness up, the vertical appears to be fine, but the horizontal stops
about three inches from both sides of the screen.

My first thought in this is that the horizontal section is not getting
enough voltage, if I turn the brightness all the way up the picture
shrinks inward even more (although it does get brighter). I posted a
picture online if you want to look at this:
http://home.comcast.net/~lj_robins/badmonitor/

One other thing is that the buttons on the front will not active the
geometric adjustment menus but they will bring it out of "sleep" mode.

Nothing appears to be burnt of fried on either side of the circuit
board, I'm not sure where to start with this thing, any suggestions?


-Landon

"lj_robins" wrote in message
. ..

I pulled the 4-pin connector off the circuit board, the Blue and Red wires
make one loop, they are reading 0.7 ohms, the Yellow and Brown wires make
the second loop, they reading 7.6 ohms.

I'm assuming and the 0.7 ohms on the red and blue wires is not normal.

I haven't done this for 40 years, but the ratio isn't abnormal. A shorted
turn would barely make a difference in resistance - you really need an
inductance meter or another yoke or other to test it. Ohms alone isn't much
help.

JR North wrote:
A 1.5 MB pic. Brilliant.
JR

lj_robins wrote:

Hi,

I'm working on a monitor for a friend of mine, she said that it
smelled like burning plastic for three days before it went bad.

The monitor:
"Proview model: 786N"
"Product no: PS720F-1s"
"Product series: DZ-777NS"

When you first turn it in the relays click like they are supposed to,
after a moment or two the little "Check signal" window pops up, but it
is scrunched on the left side and spread way apart on the right side.
The screen looks normal otherwise.

At least this is what I thought until I opened the case the turned the
brightness up, the vertical appears to be fine, but the horizontal
stops about three inches from both sides of the screen.

My first thought in this is that the horizontal section is not getting
enough voltage, if I turn the brightness all the way up the picture
shrinks inward even more (although it does get brighter). I posted a
picture online if you want to look at this:
http://home.comcast.net/~lj_robins/badmonitor/

One other thing is that the buttons on the front will not active the
geometric adjustment menus but they will bring it out of "sleep" mode.

Nothing appears to be burnt of fried on either side of the circuit
board, I'm not sure where to start with this thing, any suggestions?


-Landon


Hi JR,

Sorry, I have broadband, file size doesn't mean much to me anymore. Plus
with things like this I would rather keep the image quality good so that
details stand out.

-Landon

Homer J Simpson wrote:
"lj_robins" wrote in message
. ..

I pulled the 4-pin connector off the circuit board, the Blue and Red wires
make one loop, they are reading 0.7 ohms, the Yellow and Brown wires make
the second loop, they reading 7.6 ohms.

I'm assuming and the 0.7 ohms on the red and blue wires is not normal.

I haven't done this for 40 years, but the ratio isn't abnormal. A shorted
turn would barely make a difference in resistance - you really need an
inductance meter or another yoke or other to test it. Ohms alone isn't much
help.




Hi Homer,

I don't have either, plain old digital multimeter is all that I have.



-Landon

"lj_robins" wrote in message
. ..

Hi Homer,

I don't have either, plain old digital multimeter is all that I have.

Even a scope would help. Damn hard to fix with a DMM unless you have a lot
of experience. Still, look over the board also for burned parts. Something
made that smell.

"lj_robins" wrote in message
. ..

Hi Homer,

I don't have either, plain old digital multimeter is all that I have.

Even a scope would help. Damn hard to fix with a DMM unless you have a lot
of experience. Still, look over the board also for burned parts. Something
made that smell.







Hi again,

I have looked the whole board over and can't find anything burnt, I was
able to get that module open, it looks fine too. Everything in the high
voltage section is covered in dust (which is the norm), I'm going to
blow it out tomorrow with 120psi compressed air and then look things
over again, something might be cracked.

The smell could have been coming from an overheating transistor, but
after three days I would have thought that it would have failed, and not
just cause a display malfunction. My best guess at this point is that a
shorted capacitor is pulling the voltage down to the horz. section.

There are a hand full of solder joints in the high voltage section that
look questionable too, will deal with that tomorrow as well.


Later,

-Landon

lj_robins wrote:
"lj_robins" wrote in message
. ..

Hi Homer,

I don't have either, plain old digital multimeter is all that I have.

Even a scope would help. Damn hard to fix with a DMM unless you have a
lot of experience. Still, look over the board also for burned parts.
Something made that smell.







Hi again,

I have looked the whole board over and can't find anything burnt, I was
able to get that module open, it looks fine too. Everything in the high
voltage section is covered in dust (which is the norm), I'm going to
blow it out tomorrow with 120psi compressed air and then look things
over again, something might be cracked.

The smell could have been coming from an overheating transistor, but
after three days I would have thought that it would have failed, and not
just cause a display malfunction. My best guess at this point is that a
shorted capacitor is pulling the voltage down to the horz. section.

There are a hand full of solder joints in the high voltage section that
look questionable too, will deal with that tomorrow as well.


Later,

-Landon

Caution!: '120psi compressed air' is enough to literally blow some
components right off the board...depending on the nozzle you use. I'd
suggest vacuuming first, using a paint brush to loosen the dust. Then
use the compressed air *sparingly* to get at the hard parts.

Especially if the dust is thick, you could damage something hiding
underneath it...

jak

"jakdedert" wrote in message
.. .
lj_robins wrote:
"lj_robins" wrote in message
. ..

Hi Homer,

I don't have either, plain old digital multimeter is all that I have.

Even a scope would help. Damn hard to fix with a DMM unless you have a
lot of experience. Still, look over the board also for burned parts.
Something made that smell.







Hi again,

I have looked the whole board over and can't find anything burnt, I was
able to get that module open, it looks fine too. Everything in the high
voltage section is covered in dust (which is the norm), I'm going to blow
it out tomorrow with 120psi compressed air and then look things over
again, something might be cracked.

The smell could have been coming from an overheating transistor, but
after three days I would have thought that it would have failed, and not
just cause a display malfunction. My best guess at this point is that a
shorted capacitor is pulling the voltage down to the horz. section.

There are a hand full of solder joints in the high voltage section that
look questionable too, will deal with that tomorrow as well.


Later,

-Landon

Caution!: '120psi compressed air' is enough to literally blow some
components right off the board...depending on the nozzle you use. I'd
suggest vacuuming first, using a paint brush to loosen the dust. Then use
the compressed air *sparingly* to get at the hard parts.

Especially if the dust is thick, you could damage something hiding
underneath it...

jak


Maybe use caution too with any "moisture" in that "compressed air". Use a
"FILTER"......... I'd go with the other guys, be careful..............

lj_robins wrote:

I'm working on a monitor for a friend of mine, she said that it smelled
like burning plastic for three days before it went bad.

There should be at least one part that suffered from thermal abuse,.

When you first turn it in the relays click like they are supposed to,
after a moment or two the little "Check signal" window pops up, but it
is scrunched on the left side and spread way apart on the right side.
The screen looks normal otherwise.

The geometry correction has a faulty part .........

One other thing is that the buttons on the front will not active the
geometric adjustment menus but they will bring it out of "sleep" mode.

or it doesn't get a signal because the processor doesn't get the
input, cannot handle it on, or it cannot be obeyed.
The monitors I know have some of this circuitry towards very the front
of the board, right under the CRT, very unaccessible without taking
the board out :-(.

Best wishes,
H.

check your caps on the horizontal side of the deflection yoke.


I had a viewsonic P775 do that stupid ****, but it would also take out the
HOT after a bit. turned out to be a couple of those notorious blue HV caps.



"lj_robins" wrote in message
. ..
Hi,

I'm working on a monitor for a friend of mine, she said that it smelled
like burning plastic for three days before it went bad.

The monitor:
"Proview model: 786N"
"Product no: PS720F-1s"
"Product series: DZ-777NS"

When you first turn it in the relays click like they are supposed to,
after a moment or two the little "Check signal" window pops up, but it is
scrunched on the left side and spread way apart on the right side. The
screen looks normal otherwise.

At least this is what I thought until I opened the case the turned the
brightness up, the vertical appears to be fine, but the horizontal stops
about three inches from both sides of the screen.

My first thought in this is that the horizontal section is not getting
enough voltage, if I turn the brightness all the way up the picture
shrinks inward even more (although it does get brighter). I posted a
picture online if you want to look at this:
http://home.comcast.net/~lj_robins/badmonitor/

One other thing is that the buttons on the front will not active the
geometric adjustment menus but they will bring it out of "sleep" mode.

Nothing appears to be burnt of fried on either side of the circuit board,
I'm not sure where to start with this thing, any suggestions?


-Landon

I follow what the rest are saying. a scope would be very handy in this
situation. you could easily see overloading in the output waveform if the
yoke is shorted.

but one thing I noticed too is the raster is awful bright.


"Mike" wrote in message
...
check your caps on the horizontal side of the deflection yoke.


I had a viewsonic P775 do that stupid ****, but it would also take out the
HOT after a bit. turned out to be a couple of those notorious blue HV
caps.



"lj_robins" wrote in message
. ..
Hi,

I'm working on a monitor for a friend of mine, she said that it smelled
like burning plastic for three days before it went bad.

The monitor:
"Proview model: 786N"
"Product no: PS720F-1s"
"Product series: DZ-777NS"

When you first turn it in the relays click like they are supposed to,
after a moment or two the little "Check signal" window pops up, but it is
scrunched on the left side and spread way apart on the right side. The
screen looks normal otherwise.

At least this is what I thought until I opened the case the turned the
brightness up, the vertical appears to be fine, but the horizontal stops
about three inches from both sides of the screen.

My first thought in this is that the horizontal section is not getting
enough voltage, if I turn the brightness all the way up the picture
shrinks inward even more (although it does get brighter). I posted a
picture online if you want to look at this:
http://home.comcast.net/~lj_robins/badmonitor/

One other thing is that the buttons on the front will not active the
geometric adjustment menus but they will bring it out of "sleep" mode.

Nothing appears to be burnt of fried on either side of the circuit board,
I'm not sure where to start with this thing, any suggestions?


-Landon

Mike wrote:
I follow what the rest are saying. a scope would be very handy in this
situation. you could easily see overloading in the output waveform if the
yoke is shorted.

but one thing I noticed too is the raster is awful bright.


"Mike" wrote in message
...
check your caps on the horizontal side of the deflection yoke.


I had a viewsonic P775 do that stupid ****, but it would also take out the
HOT after a bit. turned out to be a couple of those notorious blue HV
caps.



"lj_robins" wrote in message
. ..
Hi,

I'm working on a monitor for a friend of mine, she said that it smelled
like burning plastic for three days before it went bad.

The monitor:
"Proview model: 786N"
"Product no: PS720F-1s"
"Product series: DZ-777NS"

When you first turn it in the relays click like they are supposed to,
after a moment or two the little "Check signal" window pops up, but it is
scrunched on the left side and spread way apart on the right side. The
screen looks normal otherwise.

At least this is what I thought until I opened the case the turned the
brightness up, the vertical appears to be fine, but the horizontal stops
about three inches from both sides of the screen.

My first thought in this is that the horizontal section is not getting
enough voltage, if I turn the brightness all the way up the picture
shrinks inward even more (although it does get brighter). I posted a
picture online if you want to look at this:
http://home.comcast.net/~lj_robins/badmonitor/

One other thing is that the buttons on the front will not active the
geometric adjustment menus but they will bring it out of "sleep" mode.

Nothing appears to be burnt of fried on either side of the circuit board,
I'm not sure where to start with this thing, any suggestions?


-Landon



Hi Mike,

The raster is very bright because I turned the SCREEN adjuster knob next
to the flyback transformer up so I could see where the edges of the scan
lines were actually at. At it's normal setting the screen is black with
the little "check signal" window in the middle.

After it appears on the screen 4 or 5 times the monitor goes into sleep
mode, the high voltage shuts down and then you can hear the static
crackle as all the dust looses its static charge. If you turn the
monitor off/on or hit one of the adjuster buttons it comes right back on.

Right now it is not hooked up to a PC, so all it will do is the "Check
signal".


-Landon

Meat Plow wrote:

Well he will find poorly soldered components with 120PSI.

Heh, he'll find them somewhere on the other side of the room.

For the OP, if you dont know where to look a good starting point is to
get a schematic with voltages marked on and check around the horiz scan
to narrow it down. And check the various power lines, the horiz stage
may provide power for various things.


NT

lj_robins ha escrito:

Mike wrote:
I follow what the rest are saying. a scope would be very handy in this
situation. you could easily see overloading in the output waveform if the
yoke is shorted.

but one thing I noticed too is the raster is awful bright.


"Mike" wrote in message
...
check your caps on the horizontal side of the deflection yoke.


I had a viewsonic P775 do that stupid ****, but it would also take out the
HOT after a bit. turned out to be a couple of those notorious blue HV
caps.



"lj_robins" wrote in message
. ..
Hi,

I'm working on a monitor for a friend of mine, she said that it smelled
like burning plastic for three days before it went bad.

The monitor:
"Proview model: 786N"
"Product no: PS720F-1s"
"Product series: DZ-777NS"

When you first turn it in the relays click like they are supposed to,
after a moment or two the little "Check signal" window pops up, but it is
scrunched on the left side and spread way apart on the right side. The
screen looks normal otherwise.

At least this is what I thought until I opened the case the turned the
brightness up, the vertical appears to be fine, but the horizontal stops
about three inches from both sides of the screen.

My first thought in this is that the horizontal section is not getting
enough voltage, if I turn the brightness all the way up the picture
shrinks inward even more (although it does get brighter). I posted a
picture online if you want to look at this:
http://home.comcast.net/~lj_robins/badmonitor/

One other thing is that the buttons on the front will not active the
geometric adjustment menus but they will bring it out of "sleep" mode.

Nothing appears to be burnt of fried on either side of the circuit board,
I'm not sure where to start with this thing, any suggestions?


-Landon



Hi Mike,

The raster is very bright because I turned the SCREEN adjuster knob next
to the flyback transformer up so I could see where the edges of the scan
lines were actually at. At it's normal setting the screen is black with
the little "check signal" window in the middle.

After it appears on the screen 4 or 5 times the monitor goes into sleep
mode, the high voltage shuts down and then you can hear the static
crackle as all the dust looses its static charge. If you turn the
monitor off/on or hit one of the adjuster buttons it comes right back on.

Right now it is not hooked up to a PC, so all it will do is the "Check
signal".


-Landon

check any caps (usually rated 1kv or more) near where the horizontal
coils from the yoke attach to the mainboard. something is wrong in the
path to the horizontal yoke, (which may even have shorted turns but
repalce the caps first).

-B.

lj_robins wrote:
"lj_robins" wrote in message
. ..

Hi Homer,

I don't have either, plain old digital multimeter is all that I have.

Even a scope would help. Damn hard to fix with a DMM unless you have a
lot of experience. Still, look over the board also for burned parts.
Something made that smell.







Hi again,

I have looked the whole board over and can't find anything burnt, I was

There are a hand full of solder joints in the high voltage section that
look questionable too, will deal with that tomorrow as well.


Later,

-Landon

Hi everyone,

Thanks for the replies from everyone, the problem turned out to be bad
solder joints in the high voltage section near the flyback. Not sure
which one did it, my suspicion is that the horz. output transistor had
very little solder on one of the pins and that was what was causing the
low voltage which caused the screen the shrink.

After re-doing every bad joint I could find the monitor works fine now,
I left it on in display mode (not sleep mode) for 18 hours it still
works fine.


Thanks again.

-Landon

lj_robins wrote:
Hi,

I'm working on a monitor for a friend of mine, she said that it smelled
like burning plastic for three days before it went bad.

The monitor:
"Proview model: 786N"
"Product no: PS720F-1s"
"Product series: DZ-777NS"

When you first turn it in the relays click like they are supposed to,
after a moment or two the little "Check signal" window pops up, but it
is scrunched on the left side and spread way apart on the right side.
The screen looks normal otherwise.

At least this is what I thought until I opened the case the turned the
brightness up, the vertical appears to be fine, but the horizontal stops
about three inches from both sides of the screen.

My first thought in this is that the horizontal section is not getting
enough voltage, if I turn the brightness all the way up the picture
shrinks inward even more (although it does get brighter). I posted a
picture online if you want to look at this:
http://home.comcast.net/~lj_robins/badmonitor/

One other thing is that the buttons on the front will not active the
geometric adjustment menus but they will bring it out of "sleep" mode.

Nothing appears to be burnt of fried on either side of the circuit
board, I'm not sure where to start with this thing, any suggestions?


-Landon
Sounds like the ever famous Safety cap is leaking, I can't remember
thecaps number but it is the same as the hot Exam. if the hot is a
Q404 then the cap is a C404 those numbers are just exambles

Repair kit part no TD772 will cure this problem. Do a search on YAHOO for
'monitor repair kit TD772' (without quotes)
unless you have fixed it already.

default wrote:
Repair kit part no TD772 will cure this problem. Do a search on YAHOO for
'monitor repair kit TD772' (without quotes)
unless you have fixed it already.


Hi,

So, your repair kit is able to fix bad solder joints, had you read my
previous posting you would have known this.

Just a suggestion next time.



-Landon