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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: Sat Dec 27, 2014 12:14 pm    Post subject: Reply with quote


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redfox001 wrote:

You connect the vp13 on the PG board and it performs as expected but on the XG board it performs worse while another chip on that board performs good if I understand correct.


No quite. The VPJ13S performs the "best" on the XG board with the 30MHz overall bandwidth, putting in the VPA13 (or VPA15H) instead making the things even worse, but the VPA13 on a different board (PG xrtra) works as expected. Not the exact same VPA13 chip, but both had been used in my own PG xtra before.
No oxidation, no dust, no grime on the boards that I can see, I also cleaned a board in dishwsher without success Smile

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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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redfox001



Joined: 16 Mar 2009
Posts: 2240
Location: The Netherlands


PostLink    Posted: Sat Dec 27, 2014 2:13 pm    Post subject: Reply with quote

But you say not the exact same VPA13. Could it be a batch of VPA13 on the XG from a later production year? You might check the building years when you compare performance or see neckboards to buy Wink
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gjaky



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


PostLink    Posted: Thu Jan 01, 2015 1:08 pm    Post subject: Reply with quote

A new plan is forming...
I'll try to mate the Marquee VNB neckboards with the XG. The Marquee VNBs are without question are the best neckboards available still they are cheap.
Both the XG's neckboard and the VNB expects a 0,7V signal on the input, so this is a good starting point. Unfortunately the VNB needs different supply voltages than what is readily available in the NEC, so an auxiliary power supply will be needed. There are other differences as well, but none of these seem to be invincible at this point.

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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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Jeremy112



Joined: 28 Sep 2006
Posts: 2643
Location: Fond du Lac, WI


PostLink    Posted: Thu Jan 01, 2015 1:17 pm    Post subject: Reply with quote

Gabor your XG is exhibiting the same exact issues as my 1100 does. I know it's not right that it does, I don't get "color" streaking like you show in the 1st pic, but I do get streaking across the image coming off of black lettering or lines.

I know the machine is old and it needs complete going through. Case, I envy you with your XG since it must look nice if it has no visual defects on screen. I just have not had time to tear into it and refurb it back to being a good performer, which is something I would still love to do, because I really do like my XG.

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gjaky



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


PostLink    Posted: Thu Jan 01, 2015 1:39 pm    Post subject: Reply with quote

Jeremy112 wrote:
Gabor your XG is exhibiting the same exact issues as my 1100 does. I know it's not right that it does, I don't get "color" streaking like you show in the 1st pic, but I do get streaking across the image coming off of black lettering or lines.

I know the machine is old and it needs complete going through. Case, I envy you with your XG since it must look nice if it has no visual defects on screen. I just have not had time to tear into it and refurb it back to being a good performer, which is something I would still love to do, because I really do like my XG.


The "color" streaking issue is already resolved, it was caused by the switchable peaking network, which I entirely removed. Your 1100 don't have this. Are you sure the signal timings are right and blankings are set right etc? Streaking is most likely introduced on the GAIN CTL around the CXA1779.

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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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Jeremy112



Joined: 28 Sep 2006
Posts: 2643
Location: Fond du Lac, WI


PostLink    Posted: Thu Jan 01, 2015 1:50 pm    Post subject: Reply with quote

gjaky wrote:
Jeremy112 wrote:
Gabor your XG is exhibiting the same exact issues as my 1100 does. I know it's not right that it does, I don't get "color" streaking like you show in the 1st pic, but I do get streaking across the image coming off of black lettering or lines.

I know the machine is old and it needs complete going through. Case, I envy you with your XG since it must look nice if it has no visual defects on screen. I just have not had time to tear into it and refurb it back to being a good performer, which is something I would still love to do, because I really do like my XG.


The "color" streaking issue is already resolved, it was caused by the switchable peaking network, which I entirely removed. Your 1100 don't have this. Are you sure the signal timings are right and blankings are set right etc? Streaking is most likely introduced on the GAIN CTL around the CXA1779.


I really don't remember what the settings were at for the projector when I last used it, as honestly I stopped using it because I was having an issue with the blue Raster over-wrapping around the image, both with and without a video processor. I spent a lot of time trying to get rid of it and never did. Unfortunately while it was the most noticeable issue I had with the projector, I did notice streaking as well. Both combined made the projector undesirable to use.

I would have to set the XG back up and see again what everything is set at to try to reproduce the issue. I never did do anything to the XG besides set it up and use it. Right now its sitting on a cart in "storage" mode. I would like to get my XG working good again because I do want to use a CRT in my new theater along with my Digital PJ.

I suppose I would be of more help if I actually DID set the projector up again to be able to better tell you whats going on with it Razz

Very interesting thread though, I'll be following to see how you do on your XG.

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gjaky



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


PostLink    Posted: Wed Sep 30, 2015 7:45 pm    Post subject: Reply with quote

So a little progress have happened, I hope the things will speed up from now.
I finished drawing the schematics of the interface board between EH VNB and the signals sent / expected on NEC XG ..1-2
The nice thing about it that it will retain backward compatibility to the original NEC neckboards, no further modifications will be needed in the XG itself.

I already have a standalone +/-85V power supply which I got from Scott, that will power the VNBs.
This interface board plays double role, it creates the +/-5V power lines needed for the VNB and not readily present in the NEC and second, it adds a contrast setting function to the VNB, which is present in the original NEC neckboard.

For the contrast setting I decided to copy the circuit of the VIM 03p with the precious AD834 500MHz multiplier, only three modifications were made here: the output transistors are even faster, the gain of the output opamp is increased in favour to omit the other opamp on the VNB, and the opamp itself is changed to an even faster lower noise type. This would make the signal path even more clear and simple than in an Electrohome.



XG_VNB.pdf
 Description:
Electrohome VNB - NEC XG project interface board

Download
 Filename:  XG_VNB.pdf
 Filesize:  22.79 KB
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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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gjaky



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


PostLink    Posted: Sat Nov 07, 2015 10:07 pm    Post subject: Reply with quote

So in the meantime the PCB for the daughter board got ready, actually there are two versions...

I already built the first prototype board, modifications had to be done in the local power supply, but otherwise the circuits working quite well.
I've measured 2ns rise time at 2Vpp output, with this circuit. If we take into account the limited rise time of the oscilloscope and my pulse generator that gives about 400MHz bandwidth for this contrast control circuit,
Practically this means this circuit will hardly affect the signal bandwidth passing to the VNB.



VNB-XG-PCB.jpg
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VNB-XG-PCB.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
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gjaky



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


PostLink    Posted: Sat Jan 09, 2016 8:43 pm    Post subject: Reply with quote

Heavily modified Electrohome VNBs in a heavily modified NEC PG xtra, these neckboards should fit in the XG!






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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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redfox001



Joined: 16 Mar 2009
Posts: 2240
Location: The Netherlands


PostLink    Posted: Sat Jan 09, 2016 11:13 pm    Post subject: Reply with quote

Respect! One of the few people in the world that has the equipment to measure these very high frequencies.

Does it work now without the disturbance?

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redfox001



Joined: 16 Mar 2009
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Location: The Netherlands


PostLink    Posted: Sun Jan 10, 2016 10:53 am    Post subject: Reply with quote

One thing I have to say to everyone not having the training that Gjaky has had the voltages involved can be lethal.
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gjaky



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


PostLink    Posted: Mon Feb 22, 2016 8:15 pm    Post subject: Reply with quote

So this is how 1080P 60Hz multiburst look on my XG-VNB board's G1 output.
Source GeForce 6600GT VGA card
-The VNB is "stock" performance wise, only the needed modifications were done to perform in the XG, no further peaking mods were made.
-The daughterboard uses AD834, 2SA1765, CLC449 main parts.
-Output at ~50Vpp (20V/div vertical)
-HP 1120A FET active probe without, other loads
-What is odd is that if I add a 10pF cap on the output the overall signal shape does not change significantly.
-K output looks similar too.



performance_1080P_60_resize.jpg
 Description:
XG-VNB board G1 output @ 50Vpp, 1080p 60Hz
 Filesize:  61.44 KB
 Viewed:  7233 Time(s)

performance_1080P_60_resize.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
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redfox001



Joined: 16 Mar 2009
Posts: 2240
Location: The Netherlands


PostLink    Posted: Mon Feb 22, 2016 8:41 pm    Post subject: Reply with quote

Great! So it looks like the bandwidth problem can be solved with sound enginering in stead of replacing random components. Super!
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redfox001



Joined: 16 Mar 2009
Posts: 2240
Location: The Netherlands


PostLink    Posted: Mon Feb 22, 2016 8:50 pm    Post subject: Reply with quote

The peaking inductors are much smaller than on Barco so 10pF makes a resonance at 277MHz with 33nH. Could this mean that those neckboards can do much more? Really rf?
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gjaky



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


PostLink    Posted: Mon Feb 22, 2016 9:02 pm    Post subject: Reply with quote

At this point I'm not too concerned to push the bandwidth limits. My original goal was to replace the original neckboards with a better performing one. And since my target resolution is 1080i 96Hz (aka 1808P 48P) as seen 1080P 60Hz looks nice so the bandwidth criteria is acomplished.
There is some waviness on the grey level, that -I'm affraid- I will see on the screen too, so I have to move on with real testing.

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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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the dude



Joined: 11 Sep 2013
Posts: 179



PostLink    Posted: Mon Feb 22, 2016 10:06 pm    Post subject: Reply with quote

Hmmm, maybe i really should try adapting one of those for the barco... hmmm.
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redfox001



Joined: 16 Mar 2009
Posts: 2240
Location: The Netherlands


PostLink    Posted: Mon Feb 22, 2016 10:59 pm    Post subject: Reply with quote

the dude wrote:
Hmmm, maybe i really should try adapting one of those for the barco... hmmm.


And write a how to!

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gjaky



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


PostLink    Posted: Sun Apr 03, 2016 7:15 pm    Post subject: Reply with quote

XG-VNB card in an XG75
Green as reference with a NEC CRT amplifier
Blue is the experimental XG-VNB CRT amplifier.
1080p 60Hz.



1080p_1.jpg
 Description:
XG-VNB 1080p 60Hz
 Filesize:  223.9 KB
 Viewed:  7043 Time(s)

1080p_1.jpg



1080p_g_orig.jpg
 Description:
Green reference 1080p 60Hz
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1080p_g_orig.jpg



1.jpg
 Description:
XG-VNB in XG75
 Filesize:  256.12 KB
 Viewed:  7044 Time(s)

1.jpg



_________________
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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gjaky



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


PostLink    Posted: Sat May 28, 2016 8:27 pm    Post subject: Reply with quote

In theory all three neckboards are done. So put them into my XG135LC, but as it seems two of the three boards still have some problem with vertical blanking, as the retrace lines are clearly visible no matter what I do, otherwise all thee boards gave roughly the same output, so more or less they are working at least. Also there is some performance issue that needs to be addressed:
The below shot was taken at 1080p 110Hz, which is 310MHz pixel clock, there is some obvious peaking-like artifact, but apart from that it does not seem to be that bad... Mike Parker I'm coming! Cool





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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
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gjaky



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


PostLink    Posted: Sun May 29, 2016 2:02 pm    Post subject: Reply with quote

Hm, the blanking problem is sorted out, all three boards working now, will see if I can dial in the colors when it gets darker here...
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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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