No red gun on monitor.

[Carl Jenkins]

Hello,

I'm afraid I'm experiencing a bit of a problem with
the red gun or it's circuitry in my VGA monitor. Any
solid red colour has turned to very dark red (almost
black) and there is a slight cyan wash on the screen.
The monitor is a Panasonic PanaSync E70i (model numb.
TX-T7F22M).
My local library has not purchased the SAMs schematics
since they thought the monitor schematics collection
was too expensive. I'm a computer technician but I've
repaired lots of TV recievers and a few monitors in
the past and have some repair equipment. I can't seem
to find any web sites that have free downloads of
schematics (only DVD collections for sale). Has anyone
ever had this problem with this model monitor or
equivalent and could advise me of what to do to get
the red gun to show up again? Or does anyone know of
any sites that have monitor schematics for free download?

Well, any assistance/suggestions are appreciated.


TIA,

Carl

 

[James Sweet]

Hello,

I'm afraid I'm experiencing a bit of a problem with
the red gun or it's circuitry in my VGA monitor. Any
solid red colour has turned to very dark red (almost
black) and there is a slight cyan wash on the screen.
The monitor is a Panasonic PanaSync E70i (model numb.
TX-T7F22M).
My local library has not purchased the SAMs schematics
since they thought the monitor schematics collection
was too expensive. I'm a computer technician but I've
repaired lots of TV recievers and a few monitors in
the past and have some repair equipment. I can't seem
to find any web sites that have free downloads of
schematics (only DVD collections for sale). Has anyone
ever had this problem with this model monitor or
equivalent and could advise me of what to do to get
the red gun to show up again? Or does anyone know of
any sites that have monitor schematics for free download?

Well, any assistance/suggestions are appreciated.


TIA,

Carl

Best suggestion I can offer is to trace the red signal and see where it gets
weak. If you put a mostly white screen up you should have more or less equal
voltages all the way from the input cable to the cathode pins on the CRT,
you have three identical circuits which are relatively simple, so it should
be fairly straightforward to trace them as the color signals often go
straight to the little neck board and don't even pass through the big main
board. Of course some monitors are a real chore just to get into so YMMV.

 

[Barney]

Hello,

I'm afraid I'm experiencing a bit of a problem with
the red gun or it's circuitry in my VGA monitor. Any
solid red colour has turned to very dark red (almost
black) and there is a slight cyan wash on the screen.
The monitor is a Panasonic PanaSync E70i (model numb.
TX-T7F22M).
My local library has not purchased the SAMs schematics
since they thought the monitor schematics collection
was too expensive. I'm a computer technician but I've
repaired lots of TV recievers and a few monitors in
the past and have some repair equipment. I can't seem
to find any web sites that have free downloads of
schematics (only DVD collections for sale). Has anyone
ever had this problem with this model monitor or
equivalent and could advise me of what to do to get
the red gun to show up again? Or does anyone know of
any sites that have monitor schematics for free download?

Well, any assistance/suggestions are appreciated.


TIA,

Carl

Check the crt voltages, that should lead you to the problem (although it
could be a tube fault).

 

[NunYa Bidness]

Check the crt voltages, that should lead you to the problem (although it
could be a tube fault).

Heck dude! Get a nice, new 19" Viewsonic CRT that can be had for
less than $200 these days.

Then... try to fix the ol' dog.

You'll thank yourself.

 

[Andy Cuffe]

Hello,

I'm afraid I'm experiencing a bit of a problem with
the red gun or it's circuitry in my VGA monitor. Any
solid red colour has turned to very dark red (almost
black) and there is a slight cyan wash on the screen.
The monitor is a Panasonic PanaSync E70i (model numb.
TX-T7F22M).
My local library has not purchased the SAMs schematics
since they thought the monitor schematics collection
was too expensive. I'm a computer technician but I've
repaired lots of TV recievers and a few monitors in
the past and have some repair equipment. I can't seem
to find any web sites that have free downloads of
schematics (only DVD collections for sale). Has anyone
ever had this problem with this model monitor or
equivalent and could advise me of what to do to get
the red gun to show up again? Or does anyone know of
any sites that have monitor schematics for free download?

Well, any assistance/suggestions are appreciated.


TIA,

Carl

First, measure the cathode voltages. One should be a lot higher than
the others. If they are all about the same, the CRT is weak. I've
seen a lot of bad video output ICs in monitors. Bad soldering on the
CRT board is also common with some monitors. The good news is that
the entire video circuit is normally on the CRT board, so it's easy to
get to and trace.
Andy Cuffe

[email protected] <-- Use this address until 12/31/2005

[email protected] <-- Use this address after 12/31/2005

 

[CRaSH]

Bad soldering on the
CRT board is also common with some monitors.

The CRT socket is always a prime suspect, even if it looks good, reheat the
joints (especially on a intermittent)....

 

[Robert Baer]

Check the crt voltages, that should lead you to the problem (although it
could be a tube fault).

The loss (or intermittent failure before loss) of a color on a CRT
monitor is a common and simple problem that can be fixed without any
schematic.
In fact, a schematic cannot help.
Unplug monitor, remove case, and if you want extra safety, connect a
wire to the chassis (ground) first, and then to the HV cap on the CRT.
Unplug the circuit board from the back of the CRT and unsolder the
metal shielding box around it; there are usually tabs that need to be
untwisted as well, so that the box can be removed.
Then use solder wick to remove old solder from the socket leada at
the PCB; and then freshly re-solder them (no need to blob as much on as
was done originally).
Replace the shield can, but do not re-twist the tabs (no need, and
they could break off) - just re-solder.
If you used a safety wire, remove it from the CRT cap first, then
from ground.
Then put the case back on, and you will be in business from one to 4
years more.

If you look carefully, you will note a sponge in the back of the case
that (when on) presses against that metal case, thereby creating stress
on the solder connections from the PCB to the CRT socket.
It is that stress which aggravates electromigration of the solder,
creating the equivalent of a cold solder joint and/or open.
The reason for the sponge is to help decrease shock on the CRT during
transportation.

 

[Robert Baer]

The CRT socket is always a prime suspect, even if it looks good, reheat the
joints (especially on a intermittent)....

Better to remove old solder and re-do them all.
See my other posting here.

 

[Donald]

Try this site www.shareline.net
Donald

 

[Robert Baer]

Try this site www.shareline.net
Donald

I believe i had explained (numerous times) how problems are caused,
and how to fix them.
Look it up.