Help! Horizontal width problem

[dantheman]

I have a 25" Hantarex POLO, and the image it is putting out is too wide for the screen.  This just happened suddenly, I turned it on and it was like that one time.  The front screen adjustment doesn't make it nearly small enough.  I've put a new cap kit in, and that didn't work so I had a tech come look at it.  While trying to adjust the horizontal width coil, which was stuck fast,  the tech snapped it off the board, but the image on the screen stayed the same.  The tech said I needed a new horiz. width coil because it was stuck, but seemed to want to get out of my house as quick as possible after breaking the part and not assist me in getting a new one etc.  (a-hole)  As he's the only person in my area who does this kind of work, I can't really say $#!t to the guy in case I need his help again ever.

My question is, can you guys tell me what kind of coil I need to order to replace this, and is that in fact the problem?

[cw]

check with   bob....  www.therealbobroberts.com  for the correct coil and to order it...

[subcriminal]

This text was copied from http://slot-tech-ftp.serveftp.com:8080/monitors/adjusting%20monitors/adjusting%20monitors.htm

It may help. I'm presently trying to sort out a Hantarex MTC9000 with too wide a picture!

Adjusting the horizontal size may require a component change. While modern monitors may use a potentiometer to control the width of the picture, older monitors used an adjustable coil with a ferrite "slug" in the center (see fig. 3). Ferrite is a ceramic/iron mixture. The width of the picture is adjusted by the position of the slug within the coil. When the slug is screwed deeply into the center of the coil, the "inductance" of the coil is increased. That is to say, the position of the ferrite slug deeply within the magnetic field makes the coil act as it is "bigger" (which, electrically speaking, it is). When the slug is fully within the width coil, the picture is at its narrowest.

Withdrawing the slug has the opposite effect. As the slug is screwed back out from the middle of the width coil, the inductance of the coil decreases and the picture widens out.
Adjusting the position of the slug requires a hex alignment tool. Don't let the name scare you. It's basically just a plastic allen wrench. The alignment tools are usually sold in sets of assorted sizes. Sometimes sold as "Color TV Alignment Tools," a set costs around $8.

Do not use a metal alien key to make this adjustment! The reason for this has nothing to do with getting a shock from the metal wrench touching something it shouldn't. Rather, the electromagnetic radiation from the coil is absorbed by the metal tool and it gets hot as Hell if you leave it inserted into the slug for even a minute with the power turned on. When you grab the tool to turn it or pull it out, you burn the heck out of your finger and thumb. (Ask me how I know!)

The problem with using a coil for the width adjustment is that the amount of change that can be produced by the coil isn't really very much. Fully inserting or removing the slug changes the width of the picture by just a percent or two. However, if you need to change the width by more than that, there is a modification you can make that will radically alter the width of any monitor.

In parallel with the horizontal output transistor (between the collector and emitter) there is a capacitor called the "retrace tuning capacitor." A typical value for this capacitor is between 5,000 picofarads and 10,000 picofarads at 1,500 volts. Note that's picofarads, not microfarads.

To alter the width of the raster, all you have to do is change the value of this capacitor. A ten percent change in capacitor value will produce a proportional change in the width of the picture. Larger values will make the picture wider: Smaller values will reduce the width.