Quote:
Originally Posted by JohnCT
This reminded of an AM/FM Zenith radio I had when I was a kid. I dug it up out of a pile under dad's bench and it worked, so I put it in my room. A month later, it quit. A tube tester showed a dead 19T8 so I put one in that dad had in stock and it ran a month or two and went dead. It wasn't a filament issue, the tube just went dead - low to no emission. I bought one more 19T8 at a parts store and that one lasted a couple of months and quit. I threw the radio out.
Now, I did put a lot of hours on the radio in that two or three months, sometimes leaving it running if I forgot to shut it off during the day and I used to sleep at night with it running on low, so the run time was high.
I don't know if the 19T8 was a lousy short lived design or if something was wrong with the radio, but I didn't know anything about them other than tube swapping at that point.
John
|
What you describe here is exactly what this TV is doing with my 6T8 tubes, the only problem is that I've replaced pretty much every single paper cap in this TV and it has all new Electrolytics and I also replaced a ton of old out of tolerance resistors as well, also this TV has been barely used since I've got it up and running.
Now grant it those 6T8 tubes I had were all used tubes except for one of them so I really didn't know how many hours were actually on those tubes, the one tube that has me scratching my head about its failure is that I did have a NOS RCA 6T8 tube that someone on another electronics forum I was apart of a while back had sent me for an old Grundig Console Radio I had several years ago that had a intermittent EABC80 tube in it that was giving me troubles in that radio.
That NOS 6T8 tube failed just like the used 6T8 tubes I had, that one was the one that tested as section 2 having no emissions and sections 1, 3 and 4 had had plenty of emissions yet (it measured around the 80 to 90 marks on the emissions section of the tester's meter).
So Long story short this TV still seems to have a mysterious phantom lurking in it yet.
Another strange thing is that sometimes the audio will randomly come back on it own without me doing anything to it it'll just pop back on, but then it will go back out again if I try to adjust the IF adjustments and the screwdriver slips and hits the chassis again.
The other weird thing is that the only adjustment screw that this happens with is the 4th Video IF Adjustment Screw which is the only Video IF Adjustment Screw that is hard to turn for some reason, and is the only Video IF Adjustment Screw I have issues with the screwdriver slipping off of when trying to adjust it, because of how hard that adjustment screw turns.