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scotttie
Joined: 26 Sep 2010
Posts: 3
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| Posted: Sun Sep 26, 2010 11:52 pm Post subject: keystone adjustment on NEC 9pg xtra |
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I am setting up a 9pg xtra being fed with a oppo bd-80. I have the initial mechanical setup complete. I am in the process of running the alignment. the keystone is way out. I can adjust it back, electronically, but I end up using most of the onscreen scale. I also hear an annoying buzzing. Is there an Potentiometer / magnet adjustment that can adust the keystone back to a more manageable level?
Is it possible that I messed up during the mechanical setup? or does it sound like I have a component going bad?
any help would be appreciated
Thanks
Scott
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Mon Sep 27, 2010 7:42 am Post subject: |
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The buzzing is caused by the capacitor (200V 47uF) next to PA connector on the def board, it should be replaced with a 470uF low-ESR type.
There is no adjustments for keystone over the menu.
Going up with resolution nec's geometry going bad also, but I would recheck the mechanical setup.
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scotttie
Joined: 26 Sep 2010
Posts: 3
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| Posted: Mon Sep 27, 2010 12:33 pm Post subject: |
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Thanks gjaky, can you tell me which of the mechanical procedures would effect keystone?
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Mon Sep 27, 2010 4:14 pm Post subject: |
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Is your projector sitting with the lenses facing the screen at a perfect 90 degree angle (Projectors rear is raised up) or do you have all 4 feet of the projector sitting flat on a table which would put the lenses at an angle to the screen.
My 9PG also made that buzzing noise but that was only when keystone was at 50% or in the middle of the slider. I never had the keystone in the middle because my 9PG was sitting on all 4s on a cart.
*gjaky* thank you! that is nice to know I can eliminate that buzz all together!
good luck scotttie and keep us up to date 
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Sep 27, 2010 4:59 pm Post subject: |
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I would also double check the orientation of the horz and vert cables and menu settings for projector location.
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scotttie
Joined: 26 Sep 2010
Posts: 3
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| Posted: Mon Sep 27, 2010 6:04 pm Post subject: NEC position |
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Actually, it is sitting upside down on the ceiling. Not sure how much of a difference that makes besides V/H drive polarity.
I have been searching the web for a 470mF low ESR capacitor rated at 200V. I keep coming up short with one spec or the other. Does anyone have a source for this part, I hate to have to cobble 2 or more caps together to get to the value needed.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Sep 27, 2010 6:19 pm Post subject: Re: NEC position |
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| scotttie wrote: | Actually, it is sitting upside down on the ceiling. Not sure how much of a difference that makes besides V/H drive polarity.
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Actually, its the harnesses on the convergence board I'm talking about. I have seen it for myself where something not right there causes funky adjustments.
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Mon Sep 27, 2010 10:02 pm Post subject: |
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Well, the value of that capacitor is not critical, the more the better. You can also use a 330uf or so. There were threads on AVS forums about this capacitor.
In most PC PSU there are 200V 330-470uF capacitors (if psu has active PFC those caps likely low-ESR types), if you have one, you can try it.
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Wed Sep 29, 2010 12:11 am Post subject: |
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Buzzing is usually caused, in a cap, by a large current charge or discharge in a short period of time. That is what happens when there is keystone corrrection in the horizontal sweep. The original cap is 47uF. Increasing the value to 470uF will increase that charge/discharge current 10 times if it happens in the same amount of time. It would be safer to keep the same value of cap.
The original cap is a special high current capability/ low ESR/ low value (capacitance) electrolytic because way back when that was all that was available for cheap.
Now, plastic caps like that are made. Check this one:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=478-2615-ND
Not super cheap but same value as original (47 vs 50uf). Probably won't fit exactly right but surely can be wired in.
Check it out.
Scott
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Wed Sep 29, 2010 1:35 pm Post subject: |
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This is a fairly common mod -I think it is suggested by Doug Baisey.
I saw only satisfied replies about this mod.
The 10X charging current only happens at turning on -not always. The discharging current is the same as with the original 47uF cap, due to the same load.
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Sat Oct 02, 2010 4:42 am Post subject: |
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The value on the 9PG and 10PG is infact 10uF 200v, and there is no buzz that i have ever noticed with my 9PG, friend of mine also has a 9PG with the same 10uF 200V cap and no buzz, his 9PG XTRA does have a 47uF 200v there, but we havent ever set it up long enough to here any buzz.
Having said that i agree with:
| macgyver655 wrote: | | I would also double check the orientation of the horz and vert cables and menu settings for projector location. |
...cause ive also seen some whacko geometry when there are some of those plugs the wrong way and it buzzed.
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Sat Oct 02, 2010 4:58 am Post subject: Re: NEC position |
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| scotttie wrote: |
I have been searching the web for a 470mF low ESR capacitor rated at 200V. I keep coming up short with one spec or the other. Does anyone have a source for this part, I hate to have to cobble 2 or more caps together to get to the value needed. |
Doesnt have to be 200v exactly, can be anything above that, just as long as you dont go under 200v. 200v is the max voltage that capacitor can handle, if the capacitor said 400v that means it can handle 400 volts, but if its only charged at 200 volts, it will only have a potential difference between the 2 terminals of 200 volts. In short, you can use any voltage cap you like provided its the same or higher than the original.
Also, if youre searching for a 470"mF" capacitor, youre WAY off the mark, cause mF is "milli"farad and uF "micro"farad, which is what youre after. There is a pretty substantial difference between milli and micro, and that is probably why youre not finding what youre looking for.
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