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NEC XG bandwidth and signal quality improvement: DONE
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gjaky



Joined: 05 Jun 2010
Posts: 2641
Location: Budapest, Hungary


PostLink    Posted: Mon Feb 24, 2014 10:07 am    Post subject: NEC XG bandwidth and signal quality improvement: DONE Reply with quote


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As some of you already know I was all in for extending the bandwidth of my PG xtra, as I thought it can be made better, and all along the reference was the NEC XG design in the improvement. Now I have a top XG so was quite curious how is the XG doing the bandwidth thing. The result is quite amazing, so to say unbeliveable, to be short: CRAP
So far this XG doesn't show any evidence to it is able to handle high bandwidth. While the circuit design is considered superior to what is in the PG xtra.
Here are some pictures:
NEC PG xtra @ 1280x720-120Hz
NEC XG1351 @ 1280x720-120Hz

But this is only one thing, I have some bad kind of signal peaking on hard edges, and some kind of streaking as well, and none of these are dependant from signal timings.

At this point am not sure if there is some problem with the machine or this is what it can really do...



XG_peaking2.jpg
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peaking issue 2 (intentionally dark exposition)
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XG_peaking1.jpg
 Description:
peaking issue (intentionally dark exposition)
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XG_peaking1.jpg



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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB


Last edited by gjaky on Mon May 30, 2016 8:37 pm; edited 3 times in total
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CasetheCorvetteman



Joined: 09 Nov 2008
Posts: 6319
Location: Australia


PostLink    Posted: Mon Feb 24, 2014 10:33 am    Post subject: Reply with quote

Thats not normal in the slightest GÓbor. Mine doesnt do anything like that and its only an 852.
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CasetheCorvetteman



Joined: 09 Nov 2008
Posts: 6319
Location: Australia


PostLink    Posted: Mon Feb 24, 2014 10:37 am    Post subject: Reply with quote

The fact its not dependant on signal timings should illustrate the fact youve got issues there. Id be opening it up and doing abit of surgery.
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hansilili



Joined: 09 Mar 2007
Posts: 302
Location: K÷ln, Germany


PostLink    Posted: Mon Feb 24, 2014 3:19 pm    Post subject: Reply with quote

gjaky,

if it wasn't you then I 'd suppose to check astig, focus, white balance and probably reduce contrast. Maybe you have a bad ground connection on your BNC plugs (try wiggle it) but your picture doesn't look like typipical ghosting.

Can't believe this is typical for the xg though. Any pics of red and blue and higher resolutions?

rumpeli

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HD-DAVE



Joined: 16 Feb 2007
Posts: 204
Location: Delta, BC


PostLink    Posted: Mon Feb 24, 2014 9:17 pm    Post subject: Reply with quote

I too get streaking (well more like banding - across entire screen - eg bright white object like movie end credits on black background I see bands ) on my XG1351.... at 1080p (over HDMI - Moome card) its so bad as to make the picture completely unwatchable. At 1080i I get very slight streaking, and wish I could figure out how to fix it.
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gjaky



Joined: 05 Jun 2010
Posts: 2641
Location: Budapest, Hungary


PostLink    Posted: Tue Feb 25, 2014 6:31 am    Post subject: Reply with quote

It is not a setup problem really, I checked if it isn't a ground loop, but no.
I also have a Moome DVI input card, but I haven't tried yet, but I think that doesn't really matter where the signal coming from. Hopefully I could take a few measurements today, and report back.

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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB
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CasetheCorvetteman



Joined: 09 Nov 2008
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PostLink    Posted: Tue Feb 25, 2014 9:49 am    Post subject: Reply with quote

No i dont think its setup at all, i think there is something wrong.

I have the MOOME HDMI 1.3 in mine and it gives identical image quality to the RGB for me.

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gjaky



Joined: 05 Jun 2010
Posts: 2641
Location: Budapest, Hungary


PostLink    Posted: Tue Feb 25, 2014 8:09 pm    Post subject: Reply with quote

So, took some measurements. I measured 5ns rise time on the output of the CRT amplifier (Cathode), this equals to 70MHz overal bandwidth. Not great, but we have very little knowledge about real bandwidth of the machines anyway. Tomorrow will repeat this measurement on the PG xtra -which is fortunately still hanging around Smile

I measured the output of the GAIN CTL, however I not consider this to a valid measurement (got very bad rise times), but it was clear that there wasn't bandwidth loss at on/off pixels.

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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB


Last edited by gjaky on Sun Sep 14, 2014 7:56 am; edited 1 time in total
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CasetheCorvetteman



Joined: 09 Nov 2008
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Location: Australia


PostLink    Posted: Wed Feb 26, 2014 3:37 am    Post subject: Reply with quote

Youve clearly got issues.
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digitalayon



Joined: 02 Mar 2009
Posts: 892



PostLink    Posted: Wed Feb 26, 2014 5:35 am    Post subject: Reply with quote

Yeah I would check for blown caps and cold soldier joints.
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gjaky



Joined: 05 Jun 2010
Posts: 2641
Location: Budapest, Hungary


PostLink    Posted: Fri Feb 28, 2014 9:52 pm    Post subject: Reply with quote

So I recapped the green neckboard, and guess what, nothing have changed!
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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB
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CasetheCorvetteman



Joined: 09 Nov 2008
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PostLink    Posted: Sat Mar 01, 2014 2:53 am    Post subject: Reply with quote

I didnt expect that would fix it. I dont reckon that is where the issue resides.
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gjaky



Joined: 05 Jun 2010
Posts: 2641
Location: Budapest, Hungary


PostLink    Posted: Sat Mar 01, 2014 4:32 pm    Post subject: Reply with quote

CasetheCorvetteman wrote:
I didnt expect that would fix it. I dont reckon that is where the issue resides.


Then summarize the things up.
-The source signal path is the same what was with the PG xtra, only the projector have changed, so the problem is with the projector.
-The signal inside the projector goes: BNC input on the Video motherboard ->GAIN CTL->Neckboards->CRTs
-The problem is presented the same way on all tubes. With pure speculation I find it highly unlikely to have exactly the same problem on each CRT or neckboard, while no one else had a similar problem as it turned out, so clearly there is a problem somewhere.
So this leave the GAIN CTL and the Video motherboard as a suspect.
I should check out the DVI input card, how it goes (this also would rule out most of the V-motheroard) but I don't have a DVI cable, and don't know what should expect from the moome board anyway as this is a first gen. DVI/component card.

I am not able to take valid measurements, wherever I take measurements in the projector (with the absolute shortest ground wires) it starts from about 3-4ns rise time with all kinds of oscillations on it, while I am able to check that the input signal is rising under 2ns, and has an acceptable shape.

Once cheap XG parts come by I'll buy one of each boards that are in the signal path to check what's going on, until that I'll have to live with this Thumbs Down

BTW just figured out that the "aperture level" in the info menu sets the signal peaking, too bad it only can make the picture worse, at 1080i-96Hz only level 0-1 looks acceptable.

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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
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CasetheCorvetteman



Joined: 09 Nov 2008
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PostLink    Posted: Sun Mar 02, 2014 3:45 am    Post subject: Reply with quote

Mine doesnt have that setting.

If i was to guess, id have suspected the GAIN CTL board right from the start. The reason i would is cause my PG did exactly that, and it was the GAIN CTL board causing that smearing of colour and bleeding all the right side of everything.

Different as the machine may be, the GAIN CTL board is still doing the same job.

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gjaky



Joined: 05 Jun 2010
Posts: 2641
Location: Budapest, Hungary


PostLink    Posted: Sun Mar 02, 2014 8:00 am    Post subject: Reply with quote

CasetheCorvetteman wrote:
Mine doesnt have that setting.


It's on the third page of the info on mine, however not a big deal as I said...

CasetheCorvetteman wrote:

If i was to guess, id have suspected the GAIN CTL board right from the start. The reason i would is cause my PG did exactly that, and it was the GAIN CTL board causing that smearing of colour and bleeding all the right side of everything.

Different as the machine may be, the GAIN CTL board is still doing the same job.


Certainly it can be, actually it does much more than in the PG, since the video signal is not going through the VIDEO out board anymore, every setting is applied on GAIN CTL which affects brightness, contrast, etc. I've removed the injection of the optional component board, and also checked the signal on the board's input pin, and this what I was refferring: Outside the pj everything seems fine the input signal is excellent, then with the exactly same technique I probed on the input pins of GAIN CTL and it is a mess, I even inspected the V-motherboard, but of course there's nothing on it what would affect the signal. When I was probing in the PG xtra I got very similar values to the XG, with the difference the bandwidth of PG xtra looks much better on screen than XG's, so my measurements were quite useless.

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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB
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CasetheCorvetteman



Joined: 09 Nov 2008
Posts: 6319
Location: Australia


PostLink    Posted: Sun Mar 02, 2014 9:05 am    Post subject: Reply with quote

Yeah i know the one, i have seen it on Al's XG, im not sure what year model his is, but its a 1 series where as mine is a 2 series. There are a couple other things i found to be very slightly different in there too, but i cant recall those at this point cause they were reasonably insignificant to the end result.

How does the GAIN CTL board's components look and test? The capacitors in the earlier PGs were known to leak after time as you know, but i havent seen that myself on an XTRA or XG, which certainly doesnt mean they wont go bad either.

When i replaced the capacitors on my PG GAIN CTL board it made a HUGE difference to the sharpness of the image, more so at higher brightnesses, and it greatly improved the overall contrast of the image. Prior to that, id get some serious bleeding, more so on red and blue, when i pushed the contrast setting up abit. Almost every single cap on that board was leaking, so i replaced the lot.

When i completely recapped the VIDEO OUTPUT board in the PG, i saw no noticable change, however most of those were boardering on bad too. For that reason i didnt suspect you were having issues with the neck boards there, and i think youve proven that beyond doubt with your work so far.

There is clearly a problem with that set and i reckon youll have no trouble tracking it down Wink

Keep us updated!!

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gjaky



Joined: 05 Jun 2010
Posts: 2641
Location: Budapest, Hungary


PostLink    Posted: Sun Mar 02, 2014 9:20 am    Post subject: Reply with quote

Most of the caps found on GAIN CTL are working for the sync circuit, other than those there are only 5-6 that are decoupling the supply lines for the RGB circuits, the rest is DC decoupling at the input.

what I was thinking as well... As I already told you the menu high lights are also have some effect on picture (streaking wise), but the OSD is injected right before the signal goes to the neckboards, so this would suspect the output circuit or yet the neckboards. Removing the OSD signal did not improved the signal quality.

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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB
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CasetheCorvetteman



Joined: 09 Nov 2008
Posts: 6319
Location: Australia


PostLink    Posted: Sun Mar 02, 2014 9:28 am    Post subject: Reply with quote

I wouldnt think it would. What happens if you feed the RGB into the OSD circuit and connect sync to the normal spot? Youll need to blank the image somehow to see the image, as in the way the OSD does...
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gjaky



Joined: 05 Jun 2010
Posts: 2641
Location: Budapest, Hungary


PostLink    Posted: Sun Mar 02, 2014 9:42 am    Post subject: Reply with quote

CasetheCorvetteman wrote:
I wouldnt think it would. What happens if you feed the RGB into the OSD circuit and connect sync to the normal spot? Youll need to blank the image somehow to see the image, as in the way the OSD does...


Well actually this is a very good idea, need a bit tweaking, but definitely doable... don't even need any blanking because if I left the normal inputs open, they produce a black background, that is a perfect blanking.

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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
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CasetheCorvetteman



Joined: 09 Nov 2008
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PostLink    Posted: Sun Mar 02, 2014 10:14 am    Post subject: Reply with quote

Its worth a try mate, its no long term solution but it may reveal some things.

I have done this in the past with some domestic grade TVs that only had composite inputs, by connecting composite sync to the composite video input, then wiring the RGB lines to the OSD section of the TV and blanking the composite signal, you get an RGB grade image on a regular TV. Thats not what your purpose here will be, but it may just show a difference in there somewhere that could help figure out the real issue.

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