Hi folks;
This is the second RCA HDTV RPTV to have a broken blue CRT. I remember a job about two years ago where the estimating tech ordered a CRT for a Mits. I found a power supply fault that caused the tube to crack. This time it's a bit different.
You may ask why I didn't disconnect the CRTs one by one, and I say thiis, maybe there was a bit of wishful thinking, and their HVB could get damaged due to it's cheapness. The next tech put the fly in and it still shuts down immediately. He was going for the HVB but then saw fluid in the neck of the blue CRT. Just so you all know, this is one of two RCA HDTVs in which we had to replace the blue CRT for breakage ( I thought Ii disconnected the whole thing from he fly )
The other was an ITC series RPTV but the tube looked about the same.That one was cracked at the neck, but we found out later that the screen was broken as well.
So consider that a heads up on the blue CRT in RCAs. My problem now is that I have an HV short induced problem.
Now the boss is not a tech anymore, but he says something like "Alot of coolant leaked out of that thing". Hmmm. There were issues about the socket board, it was drenched with coolant but you coudn't see it. Even better it's a two sided board.
That has been taken care of, now I got a problem that may be obvious.
The ABL circuit is damaged, no doubt by the HV short. Obvously some kind of current limiting is working, just not ABL to the video.
I put the CRT in and l let it align itsellf, then it did some wierd thing and shutdown. Great huh ? OK it was coolant, but now, like I said, watching it, it is fantastic. I tuned into a terrestrial HDTV broadcast and yes, you can tell the difference. Thing that got me was how bright it is ! Damn !
You could just about watch this thing in the front lawn at noon. Then I saw WHEN it shutdown. I reduced the picture control and instead of runninng for five minutes, it runs for hours.
You know what I am looking for, some stupid buffer transistor feeding the video with ABL Possibly a shorted Zener or cap.
Did they put these components near the fly or are they on the other side of the PCB ?
Thank you, and thank you in advance. This NG has helped me quite a few times.
One more time ? (well not really only one)
JURB