As always, it was fun having you on it.
Now that the game board worked, and the power brick was all cleaned up it was time to figure out the monitor. The game originally came with an Amplifone color vector monitor. A lot of people have put in Wells Gardner 6100 color vectors however the Amplifone is different in a couple of ways. The deflection board design meant the Amplifones had a faster draw speed than the 6100’s, they had potentiometers on the deflection board which allowed you to adjust the height and width independent of the gameboard potentiometers. This lends to more flexibility in adjusting the picture. Maybe more importantly though the original Amplifone’s could run both 19” and 25” monitors. And maybe MOST importantly the 19” tubes that came with them were medium resolution (EGA)
I happened to track down an original tube and got to work:
That’s one dirty girl.
Mounted it to a frame so I could wash it off:
bperkins01 turned me onto Krud Kutter. Stuff is magic. Hit it with water, and then spray it on and use a paint brush.
Here you can see the difference between a standard resolution (CGA) on the right and the medium resolution tube (note the difference in dot pitch distance):
Also important to note is difference in phosphor color and tint. The newer TV tube that I pulled is much darker. The reason this matters is that Atari in particular put their color vector displays behind tinted glass. If you use a tube with a darker color the vectors won’t be as vibrant behind the tinted glass. Having a lighter phosphor is helpful for getting the ultra bright vector lines to come through.
The problem is that this tube was bare. No Yoke, no convergence rings, no degauss coil, and no dag wire. So had to start making some. I used some 20 gauge wire and started stripping the insulation:
As the wire was stranded I would put it in the chuck of the drill bit to twist the wires and make them more solid as I was stripping the insulation.
I used 0.084” Molex pins to crimp wires together and then break off the heads:
Bought a spring at the local Ace store and crimped the other end around the CRT’s mounting tab.
The purpose of the Dag wire is to maintain contact with the Aquadag (black looking paint on the back). CRT’s build up a static charge and the Aquadag is the conductant used, along with the wire, to remove the charge on the back of the tube and send it to ground.
I also threw on a 6100 yoke I had picked up to test before trying to do any Yoke winding. The 6100 was designed for a 100 degree tube (uncommon) whereas the Amplifone used the more standard 90 degree. This meant that while I could use it to test for a picture there was no way I was going to get the vectors to converge properly. But good enough to test.
To the right is the Amplifone clone kit I picked up from Shilmover on KLOV. I believe the deflection board is the most recent design where he moved from a larger heat sink to smaller ones with fans. Very important to make sure those are running, learned the hard way and blew some transistors.
Hooking it up is fairly intuitive in that the Molex connectors he used matched the header pins on each board. He also included some labels, and used the standard Atari .084" 15 pin Molex connector to match original harnesses (assuming you are using them).
Just make sure you hook up your degauss circuit (tiny PCB at the bottom) to your Degauss coil (borrowed that from another tube). Also make sure the HV (PCB on the left) is grounded with a wire heading back to ground on your power brick (green wire with the red connector on the left). Also solder a wire to the dag wire and run it to ground as well.
Good enough for a picture!
You may notice that everything is in white. I thought it might have been a problem with my connector but verified it was the game board. I later learned it came down to 2 bad RAM chips that I had ordered new and were bad. bperkins01 and MikeA helped in locating it, and bperkins01 was gracious enough to fix it.
I knew I needed to figure out a Yoke that would work. I had watched the same Arcade Jason video that people have referenced for winding. I wanted though to have a backup in case I couldn’t get this to work. I chose an old G07 I had to test as it had a Yoke that was similar in shape and size to an original (luckily have one on a Star Wars to reference). I also chose it because the phosphor was light enough that it could work behind tinted glass.
Fired it up with a TPG and it was pretty poor contrast:
To make sure it wasn’t a dying tube I decided to cap the monitor and see if it helped, and it did:
(had I owned a CRT rejuvenator at the time I would have skipped the last step)
Knowing that it was a good tube I proceeded to mark the yoke and convergence rings (note white fingernail polish) after I liked the picture and took measurements for position:
Let the Yoke winding begin:
For information on how to do this you can watch this video:
After putting it back together and soldering to the terminals and wires for the connector I got it setup:
Success!
Again everything was white at the time due to the output of the game, but it looked great.
With the confidence of that I decided to try it on the Amplifone medium resolution tube.
I spent many, many hours playing with the position, convergence strips, adding magnets, and couldn’t get the results I would be satisfied with. Best I could get was this (pretty good):
You can see the convergence problems at the top and bottom and sides.
For comparison here is a few yokes to see the differences:
6100 on the left, 25” yoke from a TV, Amp Yoke, and the rewound G07 yoke. You can see the differences in the inner winnings which are influenced by the shape of the ferrite cores.
More to come.....
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Topic: The Promised End....(Major Havoc) (Read 3573 times)
