[Tomcomm]

I contacted a crt rebuilder that was mentioned on the ETF site called Magnaview. Talked to Earl who has been rebuilding roundys for 25 years. When I briefly described my cutoff glow phanomination he immediately identified it as cathode contamination of the grid which produces unfocused electron emission when the grid gets heated by the cathode. This substantiates the speculation of John F, Wayne B and Andy. Earl stated emphatically that most all roundys have this glow after 10 years of operation. Its something we all have to live with as we and our roundys get older, something like arthritis.

I requested the forum members to test their roundys with a very simple procedure (even a caveman could do it). Activate TV with brightness, contrast and chroma at full ccw and view in a total blackout room for greater than 15 minutes. Got one reply that no glow was observed after 20 minutes. His crt was a very recent regunned 21FBP22 with no chance of any cathode buildup on its new grid. No one else reported observing the low level cut-off glow or if they did, would rather not comment??

I talked to Scotty about getting mine rebuilt with new original guns. He says no problem, $400 with my dud. He claims he has never observed my "glow" or even heard of the problem, but then he only scrutinizes his newly reguned rebuilts and I doubt in a total blackout room.

My 21FBP22 has not been rebuilt or had a brightener on it. It has good emission on all guns as long as the heaters run above 6.5vrms but falls off rapidly as I drop below 6.3vrms so the cathodes are pretty well depleted, near end-of life. I am now running a switched brightener which supplies 6vrms normal or 7.5vrms boosted at the crt. each gun's emission is way good and well balanced., no change in the glow intensity though.

Really the only time I notice the glow is at the start of the Digital Video Essentials test DVD during the "sunrise out of total night darkness" scene at the start of the video demo. This is a great DVD for setting up, evaluating and comparing the PQ of the early 50s 21CT55 with the 80s and 90s Sony monitors with comb filters. When they all look virtually the same, you know the roundy's PQ is truly optimized.....Tom