Quoted from Brian541:
If you can find someone local with a tube rejuvenator/tester first just to check if its worth putting time and money into the chassis would be ideal.If you rebuild the chassis and it has a weakening tube it will give you problems with the guns registering and will need replaced over time anyway.
Good Advice, but you will more than likely be wasting your time and money. Carnevils were built with really low grade CRTs. As the emissions faded, it was necessary to turn up the brightness / screen level to get the optics to trigger which is why you are seeing the retrace lines (on a washed out picture). You could probably adjust the picture to look good to the human eye, and then the optics won't work any longer. There is also a shot contrast adjustment in the game's menu that changes the difference between black and white. which can be changed to the point that you will no longer see the white text on the gray screen in the test menu so be careful.
I can't remember for sure but I think it uses a 7400 series WGM2574. If you are extremely lucky, there are two caps that go bad on those Wells Gardner monitors that provide the Video B+ to the neck board (which can cause a dim picture which causes tech to turn up the brightness). One is C310 10ufd at 250VDC and the other is C504 on the neck board 4.7ufd@200VDC. I think you should have around 165VDC across C504. If you have much less (like 100 or less), try changing both caps before doing anything else. It will be necessary to readjust Contrast, Brightness, and Screen Level (on the flyback) after making the fix.
As to rejuvination, good luck! The cathodes are so thin on those tubes that when you go to rejuvinate it, you will simply burn them away and totally loose the color. You can try Clean and Balance (not rejuvinate) and you might get lucky (much easier on the cathodes). But chances are, it will go from bad to worse. But, if you are going to toss the monitor anyway, you can take the financial risk.
Since it is a low res. 25" monitor, your best bet is to locate a much older game that uses one of the earlier CRTs with much better life in them (and can successfully be rejuvinated if necessary). Hopefully, you can find one at a local auction or off craiglist.
Another alternative is to find an old 25" CRT TV to marry the TV's CRT AND Yoke to the WG Montor PCB and metal chassis. Don't try to move the yoke over to the TVs Tube since you will more than likely never get the convergence right. Stick with better brand names as they typically used better grade glass than the generics. And you might want to avoid anything RCA or Zenith since those were pretty sorry CRTs for our industry. More than likely, the CRT in the TV saw far less hours on than a Video Game monitor. Check the ohms across both the game's Horiz and Vertical coils and see if the TV's come close. Usually, the H will be the same since both are a low res. yoke. But the Vertical values can be quite different and you will have issues if they aren't a close match (burn up the vertical drive IC or screen will be too tall).
The quantum hard drives were fairly voltage sensitive. So, you should check to see what 5V and 12V is at the Hard Drive power connector. The game is notorious for burning the edge connector fingers since voltage first comes into the logic board, and then goes back out to the coin door, guns and Hard Drive. To help this, we used to jumper the power wires going to the Jamma connector to the hard drive power connector jumper (simply done using splice connectors - the kind that let you straddle a wire and then have a knife you crimp down to join the two wires. Simply knock the dead end out of the one channel and you can join two wires side by side in a snap. You want the Blue color for that gauge wiring). Make sure you join the Red, Yellow and one Black to wires that are coming FROM the power supply, not going from the Logic Jamma out to the rest of the cabinet (coin door lights, Coin meter etc.)
A nice upgrade is to buy one of the Hard Drive eliminator kits that use a CF Flash card instead of a mechanical hard drive which will eventually fail.