Could someone help me locate this adjustment?

P

Peabody

Guest
The TV is a JVC AV-27920, and I need to change the horizontal size
so that there is less overscan.

I found the service menu, and it has vertical size and position
entries, but nothing for horizontal, or at least nothing I
recognized as that. (In case is wasn't obvious, I'm not a
professional at this.)

I've taken the back cover off, and there is no pot or other
adjustment for horizontal size, either on the main circuit board or
on the yoke. In fact, there are NO adjustments for anything except
Screen and Focus on the flyback.

Obviously I don't have the service manual, but if anyone has any
information on this TV, or a similar one, that would lead me to the
width adjustment, I would really appreciate it. I didn't realize
how much overscan there was until I hooked up a DVD player that lets
you zoom OUT. I would like to adjust most of the overscan out if
that's possible.

Thanks in advance for any suggestions.
 
In that Model it is not adjustable ,most sets are overscan.

kip

--
"Watch the return E-Mail addy its false"
"Peabody" <waybackKILLSPAM44@yahoo.com> wrote in message
news:Icmab.184654$xf.124078@lakeread04...
The TV is a JVC AV-27920, and I need to change the horizontal size
so that there is less overscan.

I found the service menu, and it has vertical size and position
entries, but nothing for horizontal, or at least nothing I
recognized as that. (In case is wasn't obvious, I'm not a
professional at this.)

I've taken the back cover off, and there is no pot or other
adjustment for horizontal size, either on the main circuit board or
on the yoke. In fact, there are NO adjustments for anything except
Screen and Focus on the flyback.

Obviously I don't have the service manual, but if anyone has any
information on this TV, or a similar one, that would lead me to the
width adjustment, I would really appreciate it. I didn't realize
how much overscan there was until I hooked up a DVD player that lets
you zoom OUT. I would like to adjust most of the overscan out if
that's possible.

Thanks in advance for any suggestions.
Click to expand...
 
Peabody:
Consumer television sets are NOT like computer monitors that let you easily
adjust all of these geometry parameters. What you are asking for is not in
the user menu or in the service menu .... and is not adjustable.
Computer monitors are adjustable because of all the different resolution
rates and picture sizes they have to work with..... consumer televisions
on the other hand work with only ONE scan rate and picture size.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


"Peabody" <waybackKILLSPAM44@yahoo.com> wrote in message
news:Icmab.184654$xf.124078@lakeread04...
The TV is a JVC AV-27920, and I need to change the horizontal size
so that there is less overscan.

I found the service menu, and it has vertical size and position
entries, but nothing for horizontal, or at least nothing I
recognized as that. (In case is wasn't obvious, I'm not a
professional at this.)

I've taken the back cover off, and there is no pot or other
adjustment for horizontal size, either on the main circuit board or
on the yoke. In fact, there are NO adjustments for anything except
Screen and Focus on the flyback.

Obviously I don't have the service manual, but if anyone has any
information on this TV, or a similar one, that would lead me to the
width adjustment, I would really appreciate it. I didn't realize
how much overscan there was until I hooked up a DVD player that lets
you zoom OUT. I would like to adjust most of the overscan out if
that's possible.

Thanks in advance for any suggestions.
Click to expand...
 
Most consumer sets are not adjustable for the Horiz size, unless it is a
very pricey model. Some of the higher end consumer sets may have some
jumpers on the circuit board, but usually these are too drastic, and should
be left at the factory position.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
=========================================


"john" <va3mmTAKEOUTTHIS@niagara.com> wrote in message
news:newscache$dg8flh$vm1$1@newsfeed.niagara.com...
In that Model it is not adjustable ,most sets are overscan.

kip

--
"Watch the return E-Mail addy its false"
"Peabody" <waybackKILLSPAM44@yahoo.com> wrote in message
news:Icmab.184654$xf.124078@lakeread04...
The TV is a JVC AV-27920, and I need to change the horizontal size
so that there is less overscan.

I found the service menu, and it has vertical size and position
entries, but nothing for horizontal, or at least nothing I
recognized as that. (In case is wasn't obvious, I'm not a
professional at this.)

I've taken the back cover off, and there is no pot or other
adjustment for horizontal size, either on the main circuit board or
on the yoke. In fact, there are NO adjustments for anything except
Screen and Focus on the flyback.

Obviously I don't have the service manual, but if anyone has any
information on this TV, or a similar one, that would lead me to the
width adjustment, I would really appreciate it. I didn't realize
how much overscan there was until I hooked up a DVD player that lets
you zoom OUT. I would like to adjust most of the overscan out if
that's possible.

Thanks in advance for any suggestions.
Click to expand...
 
If I really really really wanted to reduce the horizontal
size, even though there is no "official" adjustment for
that, how would I do it? Could I, for example, move the
yoke in? Anything else?

Sofie says...

Consumer television sets are NOT like computer monitors
that let you easily adjust all of these geometry
parameters. What you are asking for is not in the user
menu or in the service menu .... and is not adjustable.
Computer monitors are adjustable because of all the
different resolution rates and picture sizes they have
to work with..... consumer televisions on the other
hand work with only ONE scan rate and picture size.

The TV is a JVC AV-27920, and I need to change the
horizontal size so that there is less overscan.
Click to expand...
 
No ! Dont even touch the Yoke.
Move it then you will have to do
a Major purity and convergence
set up.
Just live with it.

kip

--
"Watch the return E-Mail addy its false"
 
Peabody <waybackKILLSPAM44@yahoo.com> writes:

If I really really really wanted to reduce the horizontal
size, even though there is no "official" adjustment for
that, how would I do it? Could I, for example, move the
yoke in? Anything else?
Click to expand...
DON'T touch the yoke - you'll mess up convergence.

If the horizontal is really much too wide, there may be other problems
in the power supply or deflection. Have it checked out by a professional.

In the old days, there used to be an adjustable coil in series with the
horizontal hoke windings.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the Feedback Form at repairfaq.org. Thanks.
 
In article <gbjbb.4838$a16.2080@lakeread01>, Peabody wrote:
The TV is a JVC AV-27920, and I need to change the
horizontal size so that there is less overscan.

Sofie says...
Consumer television sets are NOT like computer monitors
that let you easily adjust all of these geometry
parameters. What you are asking for is not in the user
menu or in the service menu .... and is not adjustable.
Computer monitors are adjustable because of all the
different resolution rates and picture sizes they have
to work with..... consumer televisions on the other
hand work with only ONE scan rate and picture size.

If I really really really wanted to reduce the horizontal
size, even though there is no "official" adjustment for
that, how would I do it? Could I, for example, move the
yoke in? Anything else?
Click to expand...
I had this problem many years ago with a 14" TV that I used as a
computer monitor. A character or so got chopped off one side or the other.

I added a small inductance in series with the horizontal scan coils.
I took a pot core (about 1" diameter) out of my junk box and wound some
turns on it and tried it - some effect but not enough. So I added more
turns until I got sufficient effect. I have little idea what inductance
I ended up with, but the result was quite good and didn't mess up the
picture geometry.

Be aware that the horizontal scan coils operate at a high voltage,
so if you attempt something like this do make sure you only fiddle
with the yoke connections with power off (and unplugged)! Also do not
accidentally try to run the set with the horizontal coils not
connected, this would usually blow the transistor.

Mike.
 
u1061771156 says...

In article <gbjbb.4838$a16.2080@lakeread01>, Peabody
wrote:

The TV is a JVC AV-27920, and I need to change the
horizontal size so that there is less overscan.

I had this problem many years ago with a 14" TV that I
used as a computer monitor. A character or so got
chopped off one side or the other.

I added a small inductance in series with the horizontal
scan coils. I took a pot core (about 1" diameter) out of
my junk box and wound some turns on it and tried it -
some effect but not enough. So I added more turns until
I got sufficient effect. I have little idea what
inductance I ended up with, but the result was quite
good and didn't mess up the picture geometry.
Click to expand...
Thanks, Mike.

I went to the library and got the Sams schematic for this
TV. The horizontal deflection circuit is driven from pin
32 of a Toshiba TA1242N IC. It goes through a resistive
divider to the base of the horizontal drive transistor. The
output of that is coupled to the base of the horizontal
output transistor through a small transformer.

The H output collector then drives the flyback transformer
as well as the H deflection coils. Then on the other side
of the yoke it connects through an RLC and then an RC to the
134V supply.

So from what what you said, I assume I should insert the
coil so that it is in series with the deflection coils, but
not the flyback. Would it make sense to have an adjustable
core in this coil?

With any luck I may actually be able to make this work.
 
"Peabody" <waybackKILLSPAM44@yahoo.com> wrote in message
news:Icmab.184654$xf.124078@lakeread04...
Now, what is a yoke?
 
In article <3n4cb.12753$sp2.950@lakeread04>, Peabody wrote:
u1061771156 says...

In article <gbjbb.4838$a16.2080@lakeread01>, Peabody
wrote:

The TV is a JVC AV-27920, and I need to change the
horizontal size so that there is less overscan.

I had this problem many years ago with a 14" TV that I
used as a computer monitor. A character or so got
chopped off one side or the other.

I added a small inductance in series with the horizontal
scan coils. I took a pot core (about 1" diameter) out of
my junk box and wound some turns on it and tried it -
some effect but not enough. So I added more turns until
I got sufficient effect. I have little idea what
inductance I ended up with, but the result was quite
good and didn't mess up the picture geometry.

Thanks, Mike.

I went to the library and got the Sams schematic for this
TV. The horizontal deflection circuit is driven from pin
32 of a Toshiba TA1242N IC. It goes through a resistive
divider to the base of the horizontal drive transistor. The
output of that is coupled to the base of the horizontal
output transistor through a small transformer.

The H output collector then drives the flyback transformer
as well as the H deflection coils. Then on the other side
of the yoke it connects through an RLC and then an RC to the
134V supply.

So from what what you said, I assume I should insert the
coil so that it is in series with the deflection coils, but
not the flyback. Would it make sense to have an adjustable
core in this coil?
Click to expand...
Right, don't fiddle with the rest of the circuit just add
inductance in series with the H deflection coils. A pot core is
ideal as it keeps the flux within the core, a toroid would do too
but is harder to wind. An "open" magnetic circuit (such as winding
on a ferrite rod) is less good as the flux will spill out and
you then need to keep it away from the tube. Adjustable would be
fine if you can find a suitable core. You do need to ensure the
core doesn't saturate with the max current (which may be of the
order of an amp or so) or it'll have a weird effect on horizontal
linearity - in fact a saturating core was used to adjust linearity
in olden days.

Mike.
P.S. Apologies for (new) munged address, remove the _ for email.
I've had to abandon my u1061771156 address. :-(
 
Remove all _ for valid address says...

Right, don't fiddle with the rest of the circuit just
add inductance in series with the H deflection coils. A
pot core is ideal as it keeps the flux within the core,
a toroid would do too but is harder to wind. An "open"
magnetic circuit (such as winding on a ferrite rod) is
less good as the flux will spill out and you then need
to keep it away from the tube. Adjustable would be fine
if you can find a suitable core. You do need to ensure
the core doesn't saturate with the max current (which
may be of the order of an amp or so) or it'll have a
weird effect on horizontal linearity - in fact a
saturating core was used to adjust linearity in olden
days.
Click to expand...
Thanks very much. I'll have to look in the junque box to
see what's available, but I'm sure I can get something that
will work.
 
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