Missing green color from WG K7400

JedahDoma

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So I recently re-capped the Wells Gardner 7400 in my Crisis Zone machine. First and foremost made a huge difference. Only problem now is I now see I'm missing the green color.

IMG_20120714_221700.jpg


As you can see the monitor test yields a red, white, and blue with no green up top. While patriotic it makes the game look odd. Anyone have an idea as the to cause of the missing green?

Thanks in advance!
 
Look on your neckboard. There's three large resistors, and three large transistors that will be burnt all to shit. Check the solder on all of those, it's a pretty common problem.
 
Look on your neckboard. There's three large resistors, and three large transistors that will be burnt all to shit. Check the solder on all of those, it's a pretty common problem.
Got to it before I did. lol I would highly doubt that the green gun went totally bad so I would think the neck board as well.

PS. Good game!
 
Thanks for the heads up. I did some checking and from what I can see the neckboard looks very clean. I didn't notice any major issues but I did snap a picture just in case I missed something.

IMG_20120714_233309.jpg


P.S.S. One of my favorites of all time. Takes Time Crisis to a new level. Now to only get that motor in the gun working. ^_^
 
You should check the resistors and make sure they are within tolerance. And check your transistors and see if any of them are open.
 
It can also be a bad solder joint where your video plugs in, or where the wires come from the main board up to the neck board. Also it could be a bad connection on the game cage, but the way this set up is that's unlkely.

Have somebody watch that nice test screen you've got, and wiggle the wires going to the neckboard, and wiggle the wires going to the video connector. That's the technical term, wiggle.
 
It can also be a bad solder joint where your video plugs in, or where the wires come from the main board up to the neck board. Also it could be a bad connection on the game cage, but the way this set up is that's unlkely.

Have somebody watch that nice test screen you've got, and wiggle the wires going to the neckboard, and wiggle the wires going to the video connector. That's the technical term, wiggle.

Oh I had them jiggle the wires instead of wiggle them.

I feel like such a n00b. ^_^

I'll do some experimenting and see what I can find out. Thanks again.
 
Thanks for the heads up. I did some checking and from what I can see the neckboard looks very clean. I didn't notice any major issues but I did snap a picture just in case I missed something.

IMG_20120714_233309.jpg


P.S.S. One of my favorites of all time. Takes Time Crisis to a new level. Now to only get that motor in the gun working. ^_^

That's the front; look at the solder, particularly around the middle (green) transistor. The traces, also.

In that photo I can see that the PCB is brown and discoloured.

On these neckboards green is usually the colour to go first. My theory is because it's nestled between two other hot transistors, and can't cool as efficiently as the two who don't have that issue.
 
Yes, on the K7400, missing color is most likely due to bad traces on the transistors circled to the left in the pic below. The 2nd most common reason is due to a broken color pot. 3rd most is a bad transistor circled to the right...

7400neckboard.jpg
 
Yes, on the K7400, missing color is most likely due to bad traces on the transistors circled to the left in the pic below. The 2nd most common reason is due to a broken color pot. 3rd most is a bad transistor circled to the right...

Any idea where one might procure said bad transistor? I tried to hunt it down for myself to no avail.
 
was the green missing before the recap? If not, you may have broken the trace on the solder side of the neck board since it is often lifted and fragile from years in service. You can short the drive transistor momentarily and watch the screen to see if the color comes on. You may have bent a pin on the tube while replacing the neck board asl well. Another quick way to "test" the drive transistors is to momentarily touch the heat sink on each one of the drive transistors for a brief moment to see if it is getting warm. If one is cold...its not getting driven or has a broken connection. good luck.....
 
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