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Discussion Starter · #1 ·
I've got a Casper image about a 1/4 inch to the right of the actual image. Most evident on high contrast. I'm all tweaked out.

I've had this since my original installation, 2 projectors, 2DVD's and 2 processors ago. The original pj was fed via s-video and this pj is fed with RGBHV from DVDO V2. The ghost is not there when the pj's internal test pattern is up only from a fed signal. I've isolated grounds, replaced cables, moved cables, cussed, cursed and prayed (just in case). This is the only thing keeping me from getting a truly stunning picture. I originally thought this was a ringing artifact but on closer inspection appears to be a ghost.

Who ya gonna call, Ghost Busters? NOPE AVS Forum...;) :D


Chip S.
 

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Guys!


If what you are seeing is chroma misplaced to either side of the luminance, then you need to adjust "chroma phase", this should be a service adjustment in your DVD player, or check the DVDO book to see if it is adjustable in the doubler.


Tim at E-Tech Phoenix
 

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Discussion Starter · #3 ·
Hi Tim,

Thanks for the quick reply. I had this with a LCD pj first and with no line doubler. The ghost is also there when viewing DBS. Why does this S**T always happen to me?


Chip S.
 

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Just curious, But are you using a motorized screen? I did an install recently where the projector was plugged into the same outlet that the screen had the junction box attached too,big mistake!

Wayne
 

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That's the damndest thing I've ever heard! Suppose you take a DVD player and just hook up S video with a 6 foot cable (or DVDO with a short cable) and nothing else. Still there? Whether it is or not, it beats me.


Chuck
 

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Discussion Starter · #6 ·
Well tonight I'm going to buy a new DVD player for the living room.

I'll try to hook it up tonight or tomorrow night all by itself. It will have to be run through the DVDO first as I only have RGBHV connections on my pj. However I think I did this a couple of years ago with no improvement. I wonder if I may be bringing something in with the power? Not on a dedicated line but nothing else is on it when watching movies. Hmmm recessed lights on 2 three way dimmer switchs w/lighted toggles, same circuit... I think I'll try that first. I have one line that I know is clean.


Chip S.
 

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Quote:
Originally posted by stefuel
I wonder if I may be bringing something in with the power? Not on a dedicated line but nothing else is on it when watching movies. Hmmm recessed lights on 2 three way dimmer switchs w/lighted toggles, same circuit... I think I'll try that first. I have one line that I know is clean.
It wouldn't cause a "ghost," and if it dimmers are a factor, the ghost would change/get better/worse as you chnge the dimmer level.


Chuck
 

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Are the cables you are using 75ohms??

Sounds like an impedance or termination problem, especially if the images are to the right of the main picture.

If not what are the common factors with all your setups


John
 

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Discussion Starter · #9 ·
There is nothing common to the current installation, not even placement. My old system was shelf mounted on the other side of the room. the new system is rack mounted(all new components and cables).:confused:


Chip S.
 

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I have this exact same problem with my GP-3000. And I've tried everything you've said (except the isolated ground). Though I did reset most of the screws in the projector as well as ribbon cables.


Chip: When the test pattern is up, try driving your brightness/contrast up.. tell me if you see it then. I can...I also can see the signal ghosting when I have the PJ on Picture Mute.


I've tried 4 different VGA-RGBHV cables, up to a BetterCables one that cost me a small fortune. Then I tried with or without the NEC Switcher, then I bought a couple Extron 109Pluses.. same problem. Still there.


I also did the SVideo test as someone here suggested.. although the Svideo was a "darker" image to start with, once I bumped up the B and C I could see the ghosting again.


Mike Newman has suggested terminating at the PJ. I've asked him how to do that a couple times, but no response. So I dunno if that works or not.


My next step is to replace the circuit boards one-by-one until the problem is found. Luckily the guy who sold the unit to me (KBK) has offered up the pieces of a unit with crap tubes to experiment with. I'm hoping I find the solution there, but I'm thinking this is something fixable with my current hardware.
 

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Sorry Taylor,


Somehow I missed that you were still looking for an option on local termination. I don't think that's the problem anymore, based on how your troubleshooting went previously, but just for grins, you might try a local termination to see if it helps. Do this by getting 3 terminators (75 ohm bnc or F-type connectors with an adaptor to BNC) and BNC T-connectors, then plug your terminator on one side, the signal on the other side and the "T" into the input for each of R, G, & B. Good luck.
 

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Thanks Mike, sorry if I sounded a little "everyone-is-here-to-serve-me-how-dare-he-not-respond" :)


That looks easy enough. I got all happy for a second till I realized the terminators I have on hand are 50Ohm. :) D'oh.


I'll give it a shot. what's another $10 right? :) Oi...
 

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Discussion Starter · #13 ·
Ran a designated line today, NFG...

Please excuse me while I stick a pistol in my mouth.

Just kidding...


Chip S.
 

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Hey Chip,


Is the ghosting showing up on the tube faces, or just on the screen (use sunglasses to protect your eyes, and look into the lenses)? If it isn't visible there, then you are dealing with an optical aberration in the lightpath, or a reflection (forgive me if I seem to be asking some obvious questions, but this is the best way to troubleshoot). Next, what type of screen are you using?


What I'm thinking here is there has to be a common denominator between all the installations that is causing this. Is the PJ close to a source of electromagnetic energy from an adjacent room (don't discount an object on the next higher floor), or a large ferrous mass (yes, even mounting hardware should be considered)?


Darrin
 

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Another thing to do is look at each of tubes output one at a time......

See if the problem is on one color only?. If the echo is there on each separate color I guess that rules out any type of convergence errors, but it does seem strange that you have had completely different systems with the same problem.

Maybe you can stick a piece of white paper on the screen just to prove the screen itself is not causing any problems?


Just so we understand more clearly:


Is the problem present on all 3 colors separately.


Is the problem present on both internal and external test signals


Are all your AV equipment powered from the same mains source


This may seem a bit strange, but is it possible to turn the power off completely at your house and power your HT back up from a long lead run from neighbors house


Do you have any High Voltage power sources near by ie High Voltage Transmission lines etc.


Cheers

John
 

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Discussion Starter · #16 ·
OK now listen very carefully. It's not a projector problem. The condition has been there from the start. It was there with a LCD projector first. All equipment has been changed including the screen. It is there reguardless of source (DVD, DBS,OTA or VHS).

The only time the ghost is not there is when you bring up an internal test pattern or menu. Sorry for repeating myself but it appears that by the time we get to the end of the thread we've forgotten what we've read.;)


Chip S.
 

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Suggest you just continue watching the test pattern or hire in a good priest.:p


Sorry but It is a difficult problem to deal with , with out being there

If you are confident it is not the Projector it is also very unlikely to be a source problem if all has been changed.

The only thing left is the cables and you have replaced them also.

I still believe the problem is one of these things:


1- Cables are not 75ohms (even if they are marked as such)


2- Cable are very poorly shielded.


3- Cable runs are very long and terminated incorrectly (I have had a problem with a video feed the other day where a dirty outer BNC plug (the shield was not making 100% contact) caused a echo exactly as you describe.


4- RF can run up the outside of cables and cause all sorts of problems, both on power leads and video feeds.

This can usually be fixed by rapping a few turns around a donut shaped ferrite ring just before it plugs in to the projector.

You Can also buy ferrites that clip around the lead and do the same job.( Hi Fi shops use a lot of these, as do computer leads on monitors etc.....)


Also, are the cables al the same length and using 75 ohm plugs not the more common 50 ohm type (75 ohm plug usually have no plastic insulation material around the outer part of the connector, just the conntact fingers).


To prove the cables are at fault just run the shortest possible lead to the projector, even if it means holding your DVD etc up to the PRG just for the exercise.


John
 

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Chip,

this is a very strange problem. Usually, ghosting is caused by:



- cable timing (uneven R-G-B cable lengths)


- improper termination impedance


- cheap or defective cables


- a defective BNC connector


- low bandwidth video chain (routers, switchers, and other ancillary toys)


- chroma delay



However, it seems like none of the above applies in your system.

There is only one other thing that comes to mind, try grounding your system to your utility (water) pipes. You can do this by simply attaching a single wire to your nearest water pipe and connecting it to the center screw on the power plate that your system is plugged into, try this as a test. You could have a defective ground system at your home, this is a common problem in a many residence. The electrical code has been changed that from now on both the ground rod (in the ground) and water pipes (plumbing) are to be used in new residence for grounding. There was big problems with the single rod in the ground for the electrical box, some corroded away, while others did not pass the OHMS test or at present the resistance of the soil is inaduate for proper grounding.


The good thing is: you are no longer using the LCD projector:D
 

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Mike Parker stole my thunder.... I also suspect that you are suffering a bad overall house grounding - the noise has nowhere to go, so it stays.
 

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I don't believe grouning to a water pipe, changing dimmers, dedicated outlets, etc. will have any effect on what you are seeing.


It sounds like a pure unterminated cable, or more probably, a bad termination (loose ground) at your BNC connector.


Try eliminating the cables from the mix. A fairly cheap way to do this, is to use RG-59 with F connectors and adapters from the Shack. If this cures the problem, go with it.


Another thing to do is to calulate the time delay of the ghost. Standard cables have a delay of about 1.5 ns per foot. If you go through the numbers, (time for a horizontal scan, displacement of ghost compared to screen size, etc.) you can come up with a delay number. If this delay number divided by 1.5 ns/ft. is equal to the length of the cables, the cable is the problem.


Is the ghost only in one color?? or is it all colors displaced? If it is a bad connection, it is likely only one of the 3 video cables. If all 3 colors, it is likely a totally missing termination on all 3 cables, or else, the wrong impedance cable.


For an example of determining delay, lets assume you are using a line doubler, the scan rate is 31.25 Khz, and therefore a line scan takes about 1/31.25KHz=32 us. If you have a 100" screen, the width of the screen is 80". If the ghost is 1/4" displaced, the time delay is (32*10^-6 sec)/80")*1/4"=10 ns. 10ns/1.5 ns/ft.=6 2/3'


If the cable is this length, or an even multiple of this length, it is a likely cuplrit.


Bob Smith
 
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