The mod can be done in less than 10 minutes and only requires that one yoke wire be cut and then soldered to an empty conector. It is prety easy to do.
Here is how I did it for anyone else wanting to try.
Again this is for a Motorola XM501-10 Black and white monitor. I put it in my Space Invaders cabinet.
Yoke fliping (& mirroring) is basicaly just reversing the 2 wires for either the horizontal or vertical windings on a yoke. See bob roberts page on it here
http://www.arcaderestoration.com/ind...ATA=147&CBT=24
Form his page you can see that a normal color CTR yoke has 4 wires. For arguments sake we will say that those wires are a Positve(+) and a Negitive(-) for the vertical winding and a Positive and a Negitine for the horizontal winding. Thats 4 wires.
The Motorola XM501 has only 3 wires going to the yoke. A black wire for both Negitaves, a red wire for horizontal(+) and a green wire for vertical(+).
First thing we do is to split the black ground wire coming from the chassis into 2 wires. Now we have a 4 wire harness just like the color monitors.
Looking at the yoke you can see where the wires originaly conected by the color dots. there are 4 color dots 3 of wich were used. At the bottom right there is a black dot, bottom left is green, top left is red, and top right is yellow (not used).
The black dot terminal has 3 wires soldered to it. these 3 wires are the grounds for the Horizontal AND vertical windings. 2 of them are for the horizontal and one is for the vertical. They must be seperated so that we have 2 seperate circuits.
If you look at these 3 ground wires closely you will notice that 2 of them go between the two plastic yoke halves and disapear, one at the top (12:00 position) and one at the bottom (6:00 position) of the yoke. These are the 2 horizontal grounds.
The third wire goes directly to the windings in plain view, near the yellow dot and at about the 1:00 position. This is the vertical ground. You need to cut this wire as close to the black dot as possible. You now have 2 seperate circuits.
This can be virified by using your DMM on Ohms setting. Put the black probe tip on the vertical wire end you just cut and the other on the green dot. This is the vertical circuit and should measure 30 OHMs. Now place your black probe tip on the black dot and the red probe tip on the red dot and you should have about 2 OHMs. This is the horizontal circuit.
Now take the wire you cut and solder it to the yellow dot terminal that had nothing conected to it and youre done.
You now have a 4 wire harness and 4 spots on the yoke to hook them to.
If you conect one ground wire to the yellow
dot, one ground wire to the black dot, the red wire to the red dot, & the green wire to the green dot the monitor will work just like it did before modification.
To mirror the image reverse the 2 wires going to the green and yellow dot.
To flip the image reverse the wires between the red and black dots.
Hope this helps others that might be having the same problem I did. You can email me at
[email protected] with questions. I also have Hi res pics of the mod if that will help you.
