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Videodrome
Joined: 22 Feb 2023
Posts: 56
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| Posted: Sat Mar 08, 2025 11:17 am Post subject: Sony VPH-D50, blue tube, faint diagonal lines |
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The blue tube since some time has faint diagonal lines that flicker slightly.
With dark content this is barely noticeable. On light content you don't see it at all.
Any idea what could be responsible?
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Videodrome
Joined: 22 Feb 2023
Posts: 56
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| Posted: Mon Mar 10, 2025 7:09 am Post subject: |
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Some other findings about the blue tube issue,
- Test patterns do not show this glitch.
- Input changes from ifb moome card to A board component shows no improvement. Though it gets a little less noticeable, probably because the component is at 60i, while the moome is at 100i.
- It slowly increases in intensity and amount of lines, the higher I push the projector (blue only).
Maybe not related and far less of an issue: at low contrast the blue stays nearly off (contrast @ 0-20), then after a threshold the blue tube jumps in contrast. Red and green show a much more gradual change when increasing the contrast. This isn't noticeable on the screen, only when I look directly into the tube.
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virusc
Joined: 11 Apr 2007
Posts: 358
Location: Massachusetts
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| Posted: Mon Mar 10, 2025 5:22 pm Post subject: |
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They look like retrace lines. That would increase with output (brightness) increase and usually is due to over driving the signal path or the most likely a part failing or way out of spec. You can confirm this for the most part by swapping the red to blue CRT with it housing but that is a lot of effort.
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Videodrome
Joined: 22 Feb 2023
Posts: 56
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| Posted: Tue Mar 11, 2025 11:24 am Post subject: |
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I'm indeed overdriving the projector, near 150MHz vs the 100MHz spec.
However the green and red tubes show no trace of any issue, they look perfect.
The lines brightness does not increase when adjusting the overall brightness or contrast, it seems a sort of low noise that is always there, even on contrast all the way to 0.
I guess I need to take a look at the neckboards, sadly because of my setup right now, I can't easily reach these.
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