| Author |
Message |
CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
|
| Posted: Thu Feb 07, 2013 6:47 am Post subject: Astig on direct view CRTs |
|
|
Is there anything special to do here or simular to doing a monochrome projection tube?
Moving focus in and out makes image flair diagonally.
|
|
| Back to top |
|
 |
barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
|
| Posted: Thu Feb 07, 2013 9:25 am Post subject: |
|
|
Hi,
Usually You wouldn't touch the deflection system on a color CRT and there is no astig control. The only rings You'll find are those for color purity and sometimes center convergence. These rings will shift the three electron beams in a way that each of them will only hit its own phosphor color. There's nothing that is intended to control focus as all color CRTs (at least all that I would know of) have electrostatic focus. I think this is because it would be impossible to control focus magnetically when there are three electron guns inside of the tube neck.
Early models sometimes had lots of convergence controls. The later ones had the convergence correction integrated into the deflection coils and preadjusted during production (like in the picture below, source: Wikipedia)...
Regards,
barclay66
| Description: |
|
| Filesize: |
41.53 KB |
| Viewed: |
49 Time(s) |
|
|
|
| Back to top |
|
|
CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
|
| Posted: Fri Feb 08, 2013 7:11 am Post subject: |
|
|
|
Cheers, so what can be done for terrible astig on a direct view set?
|
|
| Back to top |
|
|
barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
|
| Posted: Fri Feb 08, 2013 7:26 am Post subject: |
|
|
Hi,
How does the picture appear? Can You post a picture?
As there are no astig controls there may be almost nothing You can do. But that would be very strange. I've been repairing CRT television sets for almost two decades and have never heard of such a case.
We should make sure it isn't related to some other problem like poor focus (aged electron gun), degaussing problems, color purity settings, a defective deflection coil, a defective deflection circuit, etc.
Regards,
barclay66
|
|
| Back to top |
|
|
CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
|
| Posted: Fri Feb 08, 2013 12:47 pm Post subject: |
|
|
|
Its just very soft, more so around to edges. Dot pattern via RGB defocused is not round dots.
|
|
| Back to top |
|
|
barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
|
| Posted: Sat Feb 09, 2013 10:18 pm Post subject: |
|
|
Sorry, then I don't know. I've never seen anything similar...
Regards,
barclay66
|
|
| Back to top |
|
|
CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
|
| Posted: Sun Feb 10, 2013 2:41 am Post subject: |
|
|
No problem 
|
|
| Back to top |
|
|
|
|
