Quote:
Originally Posted by DaveWM
you could try some diff IF tubes.
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Will do. I swapped the 1st & 2nd back & forth (both the originals) and didn't notice any change. The 3rd IF 6EJ7 was one of the bad ones that I replaced. I just now swapped it with the old one with the set still connected to the IF of the modulator and there are now two ghost images on the test pattern. That's a good clue!
Quote:
Originally Posted by old_tv_nut
Don't try to diagnose IF/Video problems with the crosshatch image. It will be way too sensitive to fine tuning, and will show normally negligible stuff strongly.
Looking at the strong overshoots on the program image - do they vary strongly with fine tuning or is a lot of it independent of fine tuning? If it's mostly varying, suspect IF tubes / alignment. If more constant with fine tuning, suspect video circuits.
If you have a way to inject baseband video, see what that looks like, to separate video circuit issues from IF.
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It varies strongly with fine tuning. With the tuner connected, the "ghosting" goes away completely when I fine tune it into B&W, and I can exaggerate it by fine tuning it clockwise out of tune. That's what made me decide to try hooking the modulator directly to the IF cable and try to rule out the tuner. Maybe I'm using the wrong term when I say "ghosting" - if it's called overshoot, I want to make sure I get it right.
I don't have a way to inject baseband video.
Quote:
Originally Posted by old_tv_nut
By the way, what is the program source? Beware of VHS, which can have its own overshoots.
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I'm using a DTV converter box for the OTA content, and it has USB for the jpg images of the test patterns.
Thanks for the replies guys, more food for thought.