CurtPalme.com Home Theater Forum

barclay66

Hi,

I'd like to know if the mechanical Astig adjustment (via the magnetic rings on a tube) is independent of the tube's orientation versus earth's magnetic field.

The reason I'm asking is this:
If I had a test machine and used it for dialing in the tube rings it would be great if the settings were persistent, no matter where and in which orientation the tube would be mounted later. If earth's magnetic field would have a large effect on the settings, I would always have to do the adjustment on the mounted tube (which is a major PITA if You have to do it by Yourself, especially without being able to be near the screen at the same time).

Does anyone have first hand experience on this?

BTW: If we can't get to a conclusion on this I will try myself and post the results over here...

Regards,
barclay66

P.S.
Just a fact for information: As You might know, original tubes (e.g. from VDC) came factory aligned. This would underline the possibility that later changes in orientation versus earth's magnetic filed don't interfere with the alignment. BUT: Has anyone ever cared to verify those settings after mounting the tube?

fragzero · Joined: 30 Aug 2012 Posts: 344

Ask Nashou66, i recall him saying that he had to redo astig after swapping his projectors from floor to ceiling mount.

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

I've heard a story, from a guy who worked in the hungarian Panasonic service in the heyday of the CRT TV era.
The story: Panasonic had a special magnetic simulation room, they had a database from the earth's magnetic field from each country (multiple readings / country), and they aligned the tube's magnetics according to the readings and simulated the magnetics field, so a TV had different magnet settings that were sent to the hungarian market than those which were sent to Germany.
The problem was one of the hungarian readings were made accidentally on an iron ore base so gave false reading, and this turned out when the first bunch of the tvs all needed serious magnetic correction, so a guy came from Japan, and did new measurements, his guide was whom I've heard the story. But this was about convergence...

I'm not sure how the beam shape is dependent from this. The NEC projectors that have dynamic astig also have a demagnetism coil near the tubes, that automatically activates when you set astig mode from floor to ceiling and vice versa in the menu.

barclay66 · Posted: Thu Jan 16, 2014 12:55 pm Post subject:

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

I am wondering if the dynamic astig is different in this regard from the CPC magnets? Sony G70/90 only had 2 pole part CPC phisically the rest was done electronically.
Again in the NEC I think the astig memory is not connected to the actual memory block instead, there are 5 separate memory slot for astig and you can select which to use, I don't know this for sure because I only used 1 astig setup slot so far, and the manual isn't clear on this either, but there are more presets, that I can select for a certain slot.

barclay66 · Posted: Thu Jan 16, 2014 1:19 pm Post subject:

Hi,

I don't know very much about the NEC specifics, but it seems as if the Marquee is comparable regarding the approach. Hardware (CPC Magnets) and electronic astig settings that can be stored.
What I'm now concentrating on, is the hardware part only. I have in mind of course, that the electrical alignment has to be done anyway as any combination of tube/astig coils/electronics will produce results that need to aligned...

Regards,
barclay66

**Curt Palme** · Posted: Thu Jan 16, 2014 2:27 pm Post subject:

I saw this recently. I dialed a set in perfectly here at the shop, and traveled into the interior of BC and hung the set (9500LC). I had it floor mounted, projecting N-S, and at his place it was ceiling mounted, hanging E-W. The astig on the green tube was out a mile (1.62KM!) even though it was perfect here. It was a minor adjustment on the neck rings, but had I not done it on site, the astig/focus would not have been ideal.

Astig always needs to be adjusted on site for best viewing.

barclay66 · Posted: Thu Jan 16, 2014 2:52 pm Post subject:

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

Gábor, not all NECs had that degausing coil in there, i think only plus and XTRA, not plain and XG. Its there to remove residual magnetism from the steel frame of the projector.

Astig on the XG isnt tied to memory blocks ( thank f***!!! ) its a separate item in the other menu, but on my 852 i cant recall seeing any memories for multiple settings.

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

Yeah not like that on XG, but on the PG i dont believe the degauss coil is there for anything other than the fact they have some rather obvious issues with residual magnetism in their steel frame.

The fact it activates when you flip astig settings will likely be so youre starting with a clean slate as far as chassis effects goes, this way youre setting astig with no residual effect, as if you were to set it without degaussing first then did it later, your astig would be incorrect.