CurtPalme.com Home Theater Forum

chillman · Joined: 09 Apr 2007 Posts: 134 Location: Germany, Bavaria

Hi everyone,

I just realized that the cpc magnets in my Marquee are probably at the wrong position.
Right now they are all the way up to the focus coil.
As described in this link someone posted in another thread, the two pole magnet adjusts the unfocused beam to pass the "final aperture" and that the two pole magnet is supposed to sit approx. 1" ahead of this "final aperture".

Can someone explain where this final aperture sits? At the very end of the electron gun?

Also, in this thread , it is mentioned that the cpc magnets are not supposed to sit all the way up to the focus coil.

So where is the best position for the cpc magnets? Needless to say I have a hard time adjusting them...

Greetings!

Tillman

CRT_Ben · Joined: 28 Aug 2006 Posts: 1684 Location: Northern Virginia

Thanks for posting this! After reading those threads, I'm wondering the exact same thing. I wonder if this is why I'm unable to achieve good focus with my Thomas tubes!

chillman · Joined: 09 Apr 2007 Posts: 134 Location: Germany, Bavaria

What confuses me is that Electrohome seems to have mounted the cpc magnets the same way in the factory. I have a set of 8" tubes out of a 8500 which also have the cpc magnets all the way up to the focus coils, and they are glued to that position, so I think they were mounted like that in the factory. Then again, when I look into my Ampro 3600 (and also at the pics in the setup tips for the Ampro), the cpc magnets are mounted as close to the neckboards as possible.

Look at these pictures:

dvh99 · Joined: 25 Dec 2009 Posts: 2158 Location: nederland

it seems vdc did this for ease of installation and not for perfect astig if the better position would be all backwards.
if the static needs to go as far back as possible i wont hesitate to do it but i got my marquee pretty well dialed in right now and spend a lot of hours on it.
if you want to experiment plz let me know the results, cant wait to hear what happens.

David_Web · Joined: 02 May 2007 Posts: 418 Location: Sweden

Would it make any sense to use two sets of magnets. CPC at one position and 4+6pole at another? If you happen to have them =)
Plenty of room left for it.

dvh99 · Joined: 25 Dec 2009 Posts: 2158 Location: nederland

it seems to me the effect is gone or will be worse when the beam is corrected twice.
this is what my "common sense" tells me but i would like you to prove me wrong.

David_Web · Joined: 02 May 2007 Posts: 418 Location: Sweden

Well I meant using CPC (2pole) that is meant to center the beam in the aperture has one "sweetspot" where it works best.
And 4+6 pole that corrects for ovality and tiangular have another. Now it is all bundled together in a row with 2pole last.
Not to use two sets of centering magnets. (aperture flooding according to the above article)
Centering is then done by the focus coil.

km987654 · Posted: Mon May 31, 2010 10:27 am Post subject:

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

Where should i have the magnets and focus coils on my 9PG? Ive put them all back on the tubes exactly where they came off when i bled the tubes. Where is best for an NEC you think?

JustGreg · Joined: 07 Mar 2006 Posts: 3098 Location: Kenosha, WI

Once the long weekend is out of the way I"m hoping to see Scott chime in. I've scoured the net trying to find a white paper for Panny tubes ('Quee 8500) with no luck. Until someone who is in the know posts the only thing to do is experiment. I'm in a good position to do that as I'm just putzing around with a full re-install until Paul ships my almost minty G&B tubes to me. Thumbs Up

I'll throw up a dot pattern and exaggerate the spots (blobs) and post back if there's a difference when moving the CPC's farther back along the neck.

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

Ill be interested to hear your results, cause im getting quote close to installing my NEC at long last, and ill need to do the lot since ive had the tubes out. Wink

JustGreg · Joined: 07 Mar 2006 Posts: 3098 Location: Kenosha, WI

I just came from the HT and putzing with the CPC's along the tube neck as promised. I have the tubes off and the image reversed so I can read everything without getting a headache. Shocked

I have a PS3 slim, latest firmware, at 1080i via RGB, using w6rez HD 1920x1080i streamed to the PS3 using PS3 Media Server with no transcoding, (I had to rip the iso, which resulted in an AVO file, changed the extension to mpg so the PS3 would recognize it) and found that moving the CPC's did absotively nothing to the image on the tube face. NOTE: CPC's are nulled.

I thought I would see something, like a depth perception change or loss of focus; something. It appears sliding the CPC's around might only change the focal point after the face of the tube but even then I would have expected to see SOME change in pattern and text crispness. Nope.
I'll have to try it after I get the lenses back on and tackle spot size/shape. I suspect moving the CPC's will have a dramatic effect after I go through all that but that remains to be seen.

I learned one thing however, and I'm open to be corrected if I'm wrong, but all the hell we go through with magnetics (except for active image centering within the raster) is all for the benefit of flapping and definition (resolve) at the screen. (ummm, YEAHHHHhhhh!) Flapping seems to be mainly to correct the offset of the R&B tubes although a negative byproduct is edge-edge/top-bottom focusing while attempting to hand on a magnified 1:1 from the tube face image to the screen.

Most of you are probably saying "Well DUH!!" but I found it quite interesting to 'discover' this on my own. Feel free to add to this while we wait for Tim or Scott to hopefully provide a nuts and bolts of the internals of the Panny tube necks. (a technical whitepaper complete with dimensions would be nice)

**AnalogRocks** · Posted: Mon May 31, 2010 10:41 pm Post subject:

Sparky015 · Posted: Mon May 31, 2010 10:54 pm Post subject:

Watch out Greg, you don't want the forum mob jumping on you because your modding your pj! Laughing

JustGreg · Joined: 07 Mar 2006 Posts: 3098 Location: Kenosha, WI

Sparky015 · Posted: Mon May 31, 2010 11:07 pm Post subject:

did you see a difference in noise reduction? I just used some of that stuff on my diamond plate floor of my utility trailer and I have a bit left over. I would have to spray paint it after wards though. I want the PJ white to blend in with the ceiling.

Just pull me away. No more mods!

JustGreg · Joined: 07 Mar 2006 Posts: 3098 Location: Kenosha, WI

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

Cheers for posting your findings mate, until someone else tells me otherwise, ill just leave mine where they are, the picture is so damn good as it is and i havent even set the astig rings yet, they have all been moved at some stage, so itll need doing. Looks sharp and clear to me even without setting it all up!!

Mark_A_W · Posted: Tue Jun 01, 2010 10:56 am Post subject:

They go over the front "cylinder".

See pic:

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

Cheers Mark, that is pretty much exactly where mine would be, i marked their locations before i removed them from the necks first time around, and they are about the same place the Sony had it's CPCs before i pulled the tubes out of that ( which was the first time the Sony ever had it's tubes out. )