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THE MOD
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Curt Palme
CRT Tech


Joined: 08 Mar 2006
Posts: 23750
Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Sun Dec 18, 2016 7:24 pm    Post subject: Reply with quote


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All mods really need to be judged via a third neutral party like Craig Rounds, Ken Whitcomb, or someone that isn't biased towards one or the other person. Gjaky, you have made phenomenal quality PC boards by the look of it, but seeing a flickering image through a lens tells me nothing, nor do out of focus screen shots.

Have a third neutral party (or two or three) post test patterns, report back with some quantitative information and test patterns, and ideally, someone would get two sets of mods by the two parties, using the same lenses, same projector and same tubes.

How people here can't see that this is the only way to test the performance of mods is beyond me..
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gjaky



Joined: 05 Jun 2010
Posts: 2655
Location: Budapest, Hungary


PostLink    Posted: Sun Dec 18, 2016 7:53 pm    Post subject: Reply with quote

mp20748 wrote:
redfox001 wrote:
Thanks Gjaky for a brilliant and simple idea. So simple anyone could have thought of it but they didn't Wink


Not sure why this concept is being seen as a brilliant idea, when it goes completely against video circuit design for CRY technology. It's not that no one thought of it, it was done on the Dwin projector. It was safe there, but putting three video drive boards/circuits complete with input stage at each CRT socket. And considering, you're also putting three high bandwidth circuits right near and close to both deflection modules.... and let us not forget the that the input of these three separate stages goes to the VIM module to get its feed from the Moome. With this design, the noise problems that were mentioned made perfect sense.

Also and as some already know, some years back I had to attend an FCC Compliance seminar. In that seminar. Myself and other circuit designers were required to get that certification to assure you did not design a circuit that would be in violation of the FCC interference rules. That is when you really learn why some of the circuits all share the same concept, especially the higher bandwidth amplifier stages. So the concept is not new. There are several reasons why an input stage is not placed near the CRT sockets and away from the deflection stages. On the Marquee, the Canadian Rule requirement is stricter than the US. In both Interference and Radiation. That explains why the stick neck boards had the covers and the covers had two ground wires. To include why the Matquee uses Lead Shieding and no other manufacturer used the shieding. Also, it would help to know the noise issues on that chassis and why they were not a problem at the scan rates the were using during the original design concept.

So I would agree that this is a good design concept. I've said a many time, the Marquee chassis is a noise bed.


I am glad you bring up this FCC stuff. I don't know if you ever bothered to read the sticker in front of the Marquee. See picture below.
Indeed a running Marquee interferes with my FM radio on my desk, despite its strong shielding. But guess what, the NEC projectors does not harm FM reception, moreover they are passed on residental rules as well without lead shields... For that matter, when I worked on the XG project I didn't have to chase down chassis noise to operate the VNBs with daughterboards.

In the end it was possible to run the daughterboards in the Marquee after all, the fact that the Marquee is generating much electrical noise in its stock form can not be an excuse for not using delicate circuits.



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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: 2655
Location: Budapest, Hungary


PostLink    Posted: Sun Dec 18, 2016 8:03 pm    Post subject: Reply with quote

Curt Palme wrote:
All mods really need to be judged via a third neutral party like Craig Rounds, Ken Whitcomb, or someone that isn't biased towards one or the other person. Gjaky, you have made phenomenal quality PC boards by the look of it, but seeing a flickering image through a lens tells me nothing, nor do out of focus screen shots.

Have a third neutral party (or two or three) post test patterns, report back with some quantitative information and test patterns, and ideally, someone would get two sets of mods by the two parties, using the same lenses, same projector and same tubes.

How people here can't see that this is the only way to test the performance of mods is beyond me..


Thanks Curt.
That video as made in October and I did not bothered to post until yet, since it was questioned if this is working at all, so the video has the sole purpose of showing that it is ineeed working, nothing more nothing less. Smile

EDIT: I'd be happy to send my boards for a 3rd party person for challenge.

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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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draganm



Joined: 08 Mar 2006
Posts: 8781
Location: Colorado


PostLink    Posted: Mon Dec 19, 2016 12:04 am    Post subject: Reply with quote

gjaky wrote:
I hope my answer was well detailed Smile
yes thank you, it's an interesting approach.
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redfox001



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


PostLink    Posted: Mon Dec 19, 2016 12:47 pm    Post subject: Reply with quote

gjaky wrote:

In the end it was possible to run the daughterboards in the Marquee after all, the fact that the Marquee is generating much electrical noise in its stock form can not be an excuse for not using delicate circuits.


Agreed. Makes me think of the Barco where there is much less electronics between the tubes.
There are a number of reasons why I went back to Barco like drifting and noise and the punch and contrast of the image of the 909. I know bandwidth is an issue but I choose to start with good designed electronics and push the bandwidth limit as far as possible. In my opinion it is not that important in the final picture. The punch and contrast are just as important and the drift but I mentioned that Smile Hope we get this idea working on Barco. I see no need to compare mods and figure out the best (that is all marketing nonsense). We are in for the fun Very Happy Aaah forgot the focus and astig that are working so good on the 909.

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mp20748



Joined: 12 Sep 2006
Posts: 5359
Location: Maryland

TV/Projector: 9500LC Ultra / Super 02 and 03 VIM


PostLink    Posted: Tue Dec 20, 2016 6:44 pm    Post subject: Reply with quote

redfox001 wrote:
I see no need to compare mods and figure out the best (that is all marketing nonsense). We are in for the fun


I agree here and why I've been avoiding the constant request to see who's Mods are the best. It makes no sense to me, especially the animosity these comparison can create. Just hook things up and enjoy!
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gjaky



Joined: 05 Jun 2010
Posts: 2655
Location: Budapest, Hungary


PostLink    Posted: Thu Jan 05, 2017 8:29 pm    Post subject: Reply with quote

Here is some useful info.

On the picture below you can find a part of the latest VDC HDM's schematic, the circled parts are sign the difference from a standard old HDM. the most important part is the Circle 3, that serves as snubber for the switching FET, this way reducing the electrical noise into the chassis.
Circle 2 is I think standard for ULTRA HDMs.
Circle 1 is smoothing the switch on characteristics of the FET.
All parts can be found at DigiKey.

Also here is a picture about the LVPS modification. I found some nice 220uH toroidal coils in the local electronic shop, those were much smaller than the 100uH I initially tried, the current rating of these coils should be greater than 1A. For better filtering I added three caps as well (1500uF 10V for the filament and 1000uF 16V for the STBY +5V and STBY +12V), all low ESR capacitors (organic caps more preferred).

There is not much space inside, so the traces must be cut for the coils. There is no good place for the filament cap so it is best to install close to the output connector, there are several ground vias at least.
The two separate pins (far right) on the LVPS connector goes to the HVPS (warning live when plugged in!), then the second big part is for the various boards.
-The filament + is the second from right.
-I simply installed the STBY +12V 1000uF cap on the C134 cap
-I installed the STBY +5V 1000uF cap instead of C135
-I installed the STBY +5V coil close to the 5V regulator, I cutted the trace directly at the output of tha IC.
-The STBY +12V is the first for mthe right, there is plenty place for install that coil.



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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
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Location: Budapest, Hungary


PostLink    Posted: Thu Jan 05, 2017 8:46 pm    Post subject: Reply with quote

Since I ran out of the first batch PCB, I decided not to reorder those, but slightly revise the design. On the original design the gamma corrector circuit was overcomplicated that resulted in time lag between the input signal and the correction waveform got summed, that caused effective bandwidth roll-off. Also it was unpleasan that the contrast signal and the gamma setting were interacting making difficult to setup.
In the new design I tried to solve these two errors. Also added an additional blanking feature to make easier to mate the board with other projectors.




VNB_DB_V3b.pdf
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Schematic diagram of VNB-DB v3

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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 05, 2017 9:28 pm    Post subject: Reply with quote

gjaky wrote:
You always mention my "cohorts", and it is not the first time I say that I never asked anyone to form opinion neither on my work neither on yours. So if you have any evidence of the opposite please speak up, but until then this is just plain simple accusation. Meanwhile you are also welcome any posts where I said anything wrong of your work...
It is not my responsibility if there are people whom you have a problem, so don't blame me for that.

You are mixing things with my daughterboard adventures as well, history again:
In 2014 I found some major faults with my -then new to me- NEC XG 135LC's video path. After initial trials I could not solve the bandwidth issue of the neckboards, so I thought I try to mate the Marquee VNB with the NEC XG 135LC. For that an iportant step was to add contrast setting feature to the VNB, and this is where the VNB daughterboard came into the view. I was aware of that it will be difficult to do that, so I though why not do the best possible bandwidth if I do something? So I indeed went with the AD834 on a daughterboard attached to the VNB. With two year's hard work I managed to finish that project and I was happy with the end result, and this projector is working fine eversince. It was hard to do but it was fun as well, I gained a lot experience with it. But no one (except me Smile) wants to modify an NEC XG.
So I thought I should reuse all the gained experience in an other project that may actually bring some money to the kitchen. And this was when the Marquee daughter board's idea born. With konwing that the VIM input is 0.7V and the VIM output is also 0.7V I though too much things happening there for too little, so the daughterboard idea came in again.

As for how my Mod is at now... Just because I don't post 10+ blurry, out of convergence screenshots a day my modification may work, and in fact it is indeed working. Myself only have a Marquee 6500 so I didn't want to bother with screenshots with using suboptimal machine, I simply verified and measured that the concepts are working. Instead I gave mods to others who have the right machine to properly present it.
The only thing on which I still want to improve further is the gamma correction... (but that can be disabled anyway)

As I see forum member Wolfman will be getting the latest and best of your mods. I'd be happy to offer a set of my boards to Wolfman for a mod contest in January, if you agree.
So he not just could compare with your work but he could report if the "space ship is able to take off".


I'd be interested in that NEC XG bandwidth mod, I think my XG had the same issues yours was experiencing. Mine is a XG1101.

I should really keep up with whats going on around here Razz

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gjaky



Joined: 05 Jun 2010
Posts: 2655
Location: Budapest, Hungary


PostLink    Posted: Fri Jan 06, 2017 6:14 am    Post subject: Reply with quote

Jeremy112 wrote:


I'd be interested in that NEC XG bandwidth mod, I think my XG had the same issues yours was experiencing. Mine is a XG1101.

I should really keep up with whats going on around here Razz


I was under the impression that you have a 1100 (XG110 AC) those should have better video path (easy to find out by the look of neckboards), but regardless I can build either the XG-VNB board(with AD834) or this VNB-DB mod to it.
If you are indeed interested.

_________________
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: 2655
Location: Budapest, Hungary


PostLink    Posted: Fri Jan 06, 2017 7:40 pm    Post subject: Reply with quote

Jeremy112 wrote:

I'd be interested in that NEC XG bandwidth mod, I think my XG had the same issues yours was experiencing. Mine is a XG1101.

I should really keep up with whats going on around here Razz


Oh, here is something that might be interesting for you as well:
NEC XG retrace modification
There was no demand so I did not made the tutorial, but if you are interested in this I can tell you what to do, in fact I have further ideas as well...

Also I found a way to slightly reduce the power dissipation of the drive boards at lower scanrates (below 77kHz), just in case you want to get the best out of your XG Wink

_________________
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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cmjohnson



Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Fri Jan 06, 2017 9:21 pm    Post subject: Reply with quote

Just to clarify one point, it's not true that only Marquees used lead shielding. There's a strip of lead tape around the bell of every CRT in every G90. I consider some lead x-ray shielding to be a fine idea on every CRT projector.

If you want to know if such a thing is necessary, ask your local dentist's office, if they still deal with film x-rays, to give you a couple small dental film packets. Place them close to your CRTs inside your projector, and let them live there until you've put at least
eight hours of movie time on your projector with the film packs in place. Then have your dentist develop them and you'll know if there's any significant x-ray generation occurring.
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gjaky



Joined: 05 Jun 2010
Posts: 2655
Location: Budapest, Hungary


PostLink    Posted: Fri Jan 06, 2017 9:30 pm    Post subject: Reply with quote

cmjohnson wrote:
Just to clarify one point, it's not true that only Marquees used lead shielding. There's a strip of lead tape around the bell of every CRT in every G90. I consider some lead x-ray shielding to be a fine idea on every CRT projector.

If you want to know if such a thing is necessary, ask your local dentist's office, if they still deal with film x-rays, to give you a couple small dental film packets. Place them close to your CRTs inside your projector, and let them live there until you've put at least
eight hours of movie time on your projector with the film packs in place. Then have your dentist develop them and you'll know if there's any significant x-ray generation occurring.


True, NECs also have that stripe as well, but it is not that serious as in the Marquees. But x-rays are of a different concern, from the point of modifications.
I seem to remeber to a thread where a dentist put a dental film close his CRT (maybe a Marquee?) for a month or so, and there was no exposure on the film.

_________________
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: Sat Jan 07, 2017 3:36 am    Post subject: Reply with quote

Yes you are right, XG1100 (damned model numbers Razz ) However I wouldn't mind seeing what the mod would do to the 1100, I don't think the bandwidth is as good as some have said it was over the LC models, I don't have a scope to actually test it unfortunately, but I still have my suspicions Smile

Is there a difference between the xg-vnb & vnv-db mod? Or are they just different mods to bandwidth?

I'm going to check that retrace thread too, though I don't think I had that issue.

But yes I would be interested, I want to get a new (lightly used) set of tubes for the XG before I do it, since the green and (likely blue) have SimCity menu burn in from extended gaming binges (learned my lesson on the 1st movie I watched after playing that game!)

Saving up some money right now to get the tube set since this projector is now more or less a hobby projector, it won't be getting used for HT anymore, just tinkering and tweaking. I can't bring myself to get rid of it though, I have a soft spot for NEC Cool

Working on getting the set by the end of this month, so around then is when I will be picking your brain about this mod really heavily Smile
gjaky wrote:
Jeremy112 wrote:


I'd be interested in that NEC XG bandwidth mod, I think my XG had the same issues yours was experiencing. Mine is a XG1101.

I should really keep up with whats going on around here Razz


I was under the impression that you have a 1100 (XG110 AC) those should have better video path (easy to find out by the look of neckboards), but regardless I can build either the XG-VNB board(with AD834) or this VNB-DB mod to it.
If you are indeed interested.

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gjaky



Joined: 05 Jun 2010
Posts: 2655
Location: Budapest, Hungary


PostLink    Posted: Sat Jan 07, 2017 9:21 am    Post subject: Reply with quote

Jeremy112 wrote:
Yes you are right, XG1100 (damned model numbers Razz ) However I wouldn't mind seeing what the mod would do to the 1100, I don't think the bandwidth is as good as some have said it was over the LC models, I don't have a scope to actually test it unfortunately, but I still have my suspicions Smile

Is there a difference between the xg-vnb & vnv-db mod? Or are they just different mods to bandwidth?

I'm going to check that retrace thread too, though I don't think I had that issue.

But yes I would be interested, I want to get a new (lightly used) set of tubes for the XG before I do it, since the green and (likely blue) have SimCity menu burn in from extended gaming binges (learned my lesson on the 1st movie I watched after playing that game!)

Saving up some money right now to get the tube set since this projector is now more or less a hobby projector, it won't be getting used for HT anymore, just tinkering and tweaking. I can't bring myself to get rid of it though, I have a soft spot for NEC Cool

Working on getting the set by the end of this month, so around then is when I will be picking your brain about this mod really heavily Smile


The XG-VNB was made with the intention to substitute the neckboards found in the XG..1 ...2 models in a plug and play manner, and this was indeed achieved with the exception that it obviously needs an auxiliary power supply and three resistors needed to be shorted on the VIDEO OUT PWB. So it still uses the GAIN CTL of the NEC for OSD mixing and input switching.

The VNB-DB is an all-in-one solution, so the actual input signal is connected to the input of the VNB-DB and everything else is carried out internally with the simpliest and shortest path.

The XG-VNB offers more bandwidth if you are interested operating the projector beyond 1080P 72Hz, the VNB-DB tops at 1080P-72Hz "only", also from the VNB-DB luxury features like multi input had to be dropped for the sake of simplicity.

As for the XG 1100, either way there will need some interfacing to the mods. I initially tested the XG-VNB in a 9PG xtra, (that has essentially the same video path as your XG 110) so I KNOW it can be done there as well. I'm sure the VNB-DB is also can be done, but it is an untrodden path yet.

_________________
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: Mon Jan 09, 2017 3:13 am    Post subject: Reply with quote

Hmm, sounds like I would want to try the XG VNB. That extra bandwidth has me interested, though I have to admit the short signal path of the VNB DB sounds interesting too. I just don't think I can give up my multiple inputs Razz

A little hackery on the XG to get the XG VNB to work wouldn't bother me, it's sitting unused at the moment anyway, so these along with a nice set of tubes should make for a nice CRT experience again Very Happy

How does your XG look when using 1080p 72hz? Is it soft? does it look markedly noticable of a difference from 720p? I ran my XG at 1366x768 since it was a good sweet spot between 720 and 1080, and I just fed my scaler 1080p material most of the time anyway, so it gave that higher res feel Razz

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gjaky



Joined: 05 Jun 2010
Posts: 2655
Location: Budapest, Hungary


PostLink    Posted: Mon Jan 09, 2017 9:16 am    Post subject: Reply with quote

Jeremy112 wrote:
Hmm, sounds like I would want to try the XG VNB. That extra bandwidth has me interested, though I have to admit the short signal path of the VNB DB sounds interesting too. I just don't think I can give up my multiple inputs Razz

A little hackery on the XG to get the XG VNB to work wouldn't bother me, it's sitting unused at the moment anyway, so these along with a nice set of tubes should make for a nice CRT experience again Very Happy

How does your XG look when using 1080p 72hz? Is it soft? does it look markedly noticable of a difference from 720p? I ran my XG at 1366x768 since it was a good sweet spot between 720 and 1080, and I just fed my scaler 1080p material most of the time anyway, so it gave that higher res feel Razz


Looking at the resolution test patterns I always had the feeling that the XG LC was not quite as sharp as my previous 9PG xtra was and I address this to the HD-18 lens, although subjectively looking with real life materials the XG still looked better than the PG xtra and I contribute this to the better ANSI contrast as it is an LC machine.
All in all at 1080P the 1:1 pattern is not really well defined, but I’d still use this than any other „HD-ready” resolutions, since you can leave out the signal scaling out of the equation, and this is especially true if the fine details are oddly spaced (ie. 2 off : 1 on pixel pattern). The wise men say that the human eye is more sensitive to the prescence of the detail than its absolute position. Imagine an 1080P black field with one single pixel being white, this pattern converted to lower resolution will make this pixel off color (grey), and bigger of course. And although the XG may not be able to display this pixel at 1080P to be as small as it should be normally, but will be smaller than it would be at 720P plus the color tracking remains intact, so the eye will still prefer the unscaled material.

Also what was interesting with the XG-VNB mod for me is that the higher bandwidth gave little (if any) to the actual movie experience as added sharpness as I saw (although it did in the windows desktop), but what is worth noting is the color tracking changed much instead. I had a few NECs before and they all behaved roughly the same in terms of color calibration, using the XG-VNB showed a substantially different behaviour, so in the end it gave more puch to the picture to say so.

_________________
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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gregstv



Joined: 27 Aug 2007
Posts: 626
Location: Australia


PostLink    Posted: Mon Jan 09, 2017 10:07 am    Post subject: Reply with quote

I have a set of XG75 neck boards. Is it worth the effort to fit these to the XG1351. I think I remember you saying they are better neck boards.
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gjaky



Joined: 05 Jun 2010
Posts: 2655
Location: Budapest, Hungary


PostLink    Posted: Mon Jan 09, 2017 10:14 am    Post subject: Reply with quote

gregstv wrote:
I have a set of XG75 neck boards. Is it worth the effort to fit these to the XG1351. I think I remember you saying they are better neck boards.



If the XG750 was working properly then yes, although you have to change the entire back cage as well. You better check the 1351 first, I have yet to see one which performs well in terms of bandwidth, Mark_A_W also had this issue and all 8 XG..1 neckboards I have here have this problem.

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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: 2655
Location: Budapest, Hungary


PostLink    Posted: Tue Jan 10, 2017 6:48 pm    Post subject: Reply with quote

I decided to give name to the structure I am chasing, let that be true direct coupled signal chain. It refers to the fact that the input signal never gets detached from the signal chain.

Also I have now an idea that seems to be working how this structure could be transferred to the AD834 multipliers (with the lack of +Z input), sort of combinging the sterngths of my previous XG-VNB design and this VNB-DB. Doing this would offer several advantages, namely:
-To have such mod posessing a 03P VIM would NOT needed.
-Retains the true direct coupled all-in-one signal chain architecture.
-Using the AD834 directly at the neckboard, lets to omit the input opamp on the VNB, so the daughter board could directly drive the VNB output cascode stage (this was achieved in the XG-VNB project); even in fully differential manner, if desired which is obviously a further improvement / simplification of the video chain.
-Beyond 1080P 72Hz capability

The downside is that it is only a concept and I won't go into manufacturing unless someone applies saying he wants this exact mod, then I'd build it... also as it would be more complex design and the AD834 isn't exactly cheap, so the price would be inevitably higher.

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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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