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dkap
Joined: 14 Aug 2008
Posts: 109
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| Posted: Tue Dec 18, 2012 4:48 am Post subject: blue tube aimed too high? |
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I've been tinkering with a Vidikron TGS 550 D (7" Delta TAC4 tubes) to see if it's worth keeping around as a fairly mobile backup projector. I have it mostly calibrated to my liking (it really helped once I discovered the small "Test" button on the remote to access the cross hatch pattern!), but I can't lower the blue tube's aim enough with the adjustment pots to match the green or red. The result is a nice, crisp picture with a blue halo.
Could raster centering explain it?
I was tempted to try putting some washers behind the top two bolts on the blue gun as spacers to angle it down ... probably not great for dust and optics, though.
Dan
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Tue Dec 18, 2012 6:12 am Post subject: |
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There are most likely metal tabs around the main yoke that act as a master raster shift to bring the blue down. Some makes don't have it, shoot or post a couple of pix of the yoke(s) around the tubes, and I'll point them out if they are there.
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dkap
Joined: 14 Aug 2008
Posts: 109
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| Posted: Tue Dec 18, 2012 6:42 am Post subject: |
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Thanks. Hopefully, these two pics show what you need, otherwise it looks like I'll need to unscrew the circuit board to get better access.
Dan
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Vidikron - innards - a.jpg |
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Tue Dec 18, 2012 6:58 am Post subject: |
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Yup, on the top pix, see those two rings that are a dark brown? Those could be astig rings, but might also be raster centering. Try moving those slightly to see if the raster shifts around. Otherwise, some sets like the DWINs have another set of rings on the yoke closest to the lenses, which will definitely be the raster centering rings.
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dkap
Joined: 14 Aug 2008
Posts: 109
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| Posted: Tue Dec 18, 2012 7:21 am Post subject: |
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Excellent, thanks! I couldn't see any obvious movement of the raster and was about to give up on that being the correct adjustment, but I decided to recheck the picture at regular contrast and brightness just for the heck of it. I thought my eyes were deceiving me with the lack of a blue outline...  Switched back to test mode and sure enough, everything was very close to alignment. With a bit of tweaking, it's looking quite good now. The two rings can be adjusted together or separately for slightly different effect, FWIW.
Dan
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