Horizontal Width Coil???

Tighe

Well-known member
Joined
May 25, 2009
Messages
20,797
Reaction score
825
Location
Richmondville, New York
So I am making a custom cabinet for Donkey Kong '94 (Super Nintendo + Super Gameboy + Donkey Kong 94 GB cart) and I am using a TV production monitor.

It is a Panasonic CT-1920M (NMX-L23 Chassis). It has BNC composite video connectors and works great.

The problem is that Gameboy games on the Super Gameboy only take up 2/3 of the screen with a border around the outside. I want to stretch the image to fill the screen. The monitor has a vertical size pot that I was able to stretch the image to fill the screen vertically, but I cannot find the horizontal width coil as in this video to stretch the video horizontally.



Here are some photos of the chassis, can anyone be of help?

Sorry for the extra large images, but I think it is appropriate here.

IMG_20111031_224614.jpg


IMG_20111031_224623.jpg


IMG_20111031_224635.jpg


IMG_20111031_224701.jpg


IMG_20111031_224726.jpg
 
This is the only thing on the board that even looks close to a horizonal width coil . It is a coil, but there is no adjustment hole on the top. The part has "481J THL 6658P" on the top.

IMG_20111031_232916.jpg
 
Thanks Ken, What would I be looking for to find this? Are there monitors that don't have Horizontal width coils?

I'd imagine there are a lot that do not have Horizontal width coils. A TV is a fixed resolution monitor, unlike Computer and Arcade Monitors which need to support a variety of different resolutions.
 
If you can find a schematic, you may be able to adjust the size via a cap change. But I'd have to look at the circuit around the HOT to see which cap is the probable width cap...
 
If you can find a schematic, you may be able to adjust the size via a cap change. But I'd have to look at the circuit around the HOT to see which cap is the probable width cap...

Thanks! If I recall correctly the only Polypropylene capacitor I saw on the whole chassis was the one in the lower left of this photo:

IMG_20111031_232916.jpg
 
Well, if you can find something smaller than 473 (like maybe 223), you could try swapping it out to see if it helps...
 
Last edited:
In general, TV production monitors will have an "underscan-overscan" switch to control overall image size.

To be more concise, production monitors generally have as little overscan as possible, whereas normal televisions might have as much as 5%. The underscan switch is mostly used just to allow the viewing of the vertical interval so you can see that time code is present, etc. It isn't used as a size control in addition to the standard viewing adjustments.

Changing the cap isn't a bad idea, but IF the cap goes from one leg of that small transformer to ground, the width coil would have likely been placed inbetween them. Some early 4600's have that exact arrangement with no width coil, but rather a jumper (J27) just shorting across where the coil would have been to connect the transformer to the cap. You could hack in pretty much any width coil in there and get a little bit of adjustment. If you're seeking to adjust out 30% of picture width you really won't be able to achieve that; maybe 5%.

You should take a look at the Matsushita TM-202G monitor manual (Atari used them in a few games around '82 like Pole Position & Millipede) since it's chassis is very similar to what you're working on (likely derived from it as Mats = Panasonic) and see where the coil is placed. IIRC it's on the 202's satellite board and wired into the chassis.
 
Back
Top Bottom