Is this a tube problem?

[OSCAR]

I'm having a problem with a monitor, and I suspect the problem is with tube itself.  This is a W-G K4600 that I pulled the working chassis off of to replace the one in my Time Pilot.  However, I never had this monitor powered up to see if the tube was okay.

I bought a replacement chassis from Victor (8liners.com) a while back and I know that the vertical impedance of the K4600's is a bit low for his chassis and I suspect this is what causes the bad pincushion I've seen before with this chassis and my other K4600 tubes.  I've asked Vic a number of times if the lower vertical impedance (about 8.4 ohms) of the 4600 tube causes the bad pincushion effect I see, but he seems to avoid answering that...  His only response has been to place small magnets on the yoke to correct it.  

Anyway, when I connected the replacement chassis to this K4600 tube, I get a very strange display as shown below.  This pic was taken with a known working jamma board, and the monitor displays this same pic whether or not the jamma board is powered up.  Just powering up the monitor makes it display this reddish-purple screen with the horizontal lines.  None of the adjustment pots on the chassis will correct it.  So is this just a bad CRT, or possibly the chassis has been damaged?  I've gotten rid of all my spare tubes, so I can't test this chassis with any other ones, and I've been too lazy lately to pull out one of my games to swap it out with to test.

[Ken Layton]

If you turn the screen control all the way down does the picture still look the same? If so you may have a bad CRT. The tubes on the 4600 monitors were well known for developing heater leakage. Sometimes they would flash a particular color every so often when they started to go bad. Have you had this tube put on a restorer/analyzer to confirm? If the tube had an internal short, sometimes a restorer/analyzer can blast it away and make the tube good again.

[OSCAR]

Thanks for the reply, Ken.  And welcome to the forums!

I had adjusted every pot, including the screen and focus, to the extremes and the only thing that made any significant difference was the focus control.  Basically I could get the display to fuzz out the lines until they weren't visible with the focus control, but that was it.  The screen control didn't do anything, adjusted from one extreme to the other.

I was pretty sure that this was a tube problem, I was just looking for a bit of confirmation.  I haven't had an opportunity to get this tube connected to a restorer since I discovered the problem a few days ago, but I will take it to the shop and have them zap it to see if that fixes it.

Thanks again, Ken.

[Ken Layton]

If the screen control is turned all the way down and it didn't affect the picture then I think you do have a goofy picture tube. It is certainly a good idea to put it on the restorer/analyzer to see if the leakage and/or short indicators show anything. I have TWO B&K model 467 restorer/analyzers. One of them has a full set of socket adapters.