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NEC XG 135 Brightness problem
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Fri Mar 10, 2017 11:24 pm    Post subject: NEC XG 135 Brightness problem Reply with quote


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I have a strange problem with my XG135 and I wonder if any of you guys could help?

For background, I've had it installed since 2004 and it's worked perfectly until about a year or so ago. It has a Moome HDMI card I got via this site and it has medium wear on the green and blue tubes, very little wear on the red.

The problem is that the brightness is drifting up or down by itself. It happens equally on all 3 tubes so doesn't seem to be a tube specific issue.

Usually the picture gets much darker as the brightness drifts down, but it can sometimes become brighter too. I could watch 3 or 4 movies (1 per night) with no problem. then switch on a day later and the whole picture is too dark. It can sometimes drift up or down during a movie too, to a point where it becomes noticeable.

Just going into the brightness setting menu would instantly fix the problem (i believe the "AKB" option is enabled while in the brightness menu and this corrects the problem) as did enabling the AKB option for that input.

As the drifting became more common I've been running it with the AKB option enabled (trying to ignore those annoying calibration lines at the top of the screen) and that's been OK for a while, but lately the AKB calibration is becoming noticeable on a dark screen, with the automatic brightness adjustments creating slight flicker.

Tonight it was even worse and the AKB calibration was causing flicker even on a bright screen, so I turned AKB off and initially the brightness settled too high. I went into the brightness adjustment menu screen and it re-adjusted again and seemed to settle at the proper black level. Watched 2 movies and it remained totally fine throughout.

Would be grateful for any thoughts or suggestions. Thanks.
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Curt Palme
CRT Tech



Joined: 08 Mar 2006
Posts: 24296
Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Fri Mar 10, 2017 11:50 pm    Post subject: Reply with quote

Did we email about this? I emailed someone with a similar problem recently. I suspect tube issues, that the low emission is affecting the AKB. Try reseating all of the boards, but if you have over say 6000 hours on the tubes, that would be my guess.
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Fri Mar 10, 2017 11:55 pm    Post subject: Reply with quote

Curt Palme wrote:
Did we email about this? I emailed someone with a similar problem recently.


Yeah, we were talking about it via email last year and you recommended replacing all the video boards in the card cage.

I sent all the card ID numbers back in December but things went kinda dead since then and I didn't hear anything further, so I wasn't sure if you couldn't find a matching set of cards or were just busy. The cards were all re-seated when they were removed to get the ID numbers, but it didn't help, problem is still the same unfortunately.
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Sat Mar 11, 2017 12:11 am    Post subject: Reply with quote

And yes, the tubes have about 6500 hours on them.

Appears to be medium wear on green and blue but very little on red, actually hard to even see the wear on the red at all even now. The brightness problem doesn't add any colour tint to the picture as it drifts up/down, so definitely seems to be on all 3 tubes equally which made me think it wasn't an issue with the tubes, but I'm a software not a hardware guy so I really don't know for sure. Smile
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Curt Palme
CRT Tech



Joined: 08 Mar 2006
Posts: 24296
Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Sat Mar 11, 2017 1:17 am    Post subject: Reply with quote

Sorry, I did get really busy. I need to set up an NEC XGLC, but haven't had the time to do it yet. It's buried, so I need to dig it out.
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gjaky




Joined: 05 Jun 2010
Posts: 2789
Location: Budapest, Hungary


PostLink    Posted: Sat Mar 11, 2017 6:57 am    Post subject: Reply with quote

Is this an XG135LC or AC?
Regardless I'd say the problem is with the video out board or the G2 controls at HV PWB. On the Video out pwb there are a quite few pots those may get scratchy. Try reseating (all connecting cables as well). If that does not help sign with a fine tip marker where the pots were set and rotate them back and forth a few times, then set back where they were and see if it got better.

_________________
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, VIM-DB
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Sat Mar 11, 2017 8:16 pm    Post subject: Reply with quote

That sounds like a good idea to try, thanks. Will give it a go once I get someone to help me remove the hush box , so may take a week.

It's the normal AC version btw, not an LC.
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gjaky




Joined: 05 Jun 2010
Posts: 2789
Location: Budapest, Hungary


PostLink    Posted: Sat Mar 11, 2017 9:54 pm    Post subject: Reply with quote

Oh, also the GAIN CTL board can be blamed since the main brightness setting happening there.
_________________
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, VIM-DB
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Sun Mar 19, 2017 6:57 pm    Post subject: Reply with quote

Finally got a chance to play with this today.

I reseated cables and the moome hdmi board, then marked, adjusted back/forward and reset the pots on the video board and on the gain board. Also reseated the daughter card while I had the moome card out, which I hadn't done before, so all cards have now been removed and refitted.

Switched on and at first it looked perfect. Left it for about 10 minutes and then came back to check and the brightness had already drifted way too high, visible even on a bright screen and very obvious on a black screen.

Switched on AKB via menu and it immediately corrected itself and looked OK again. Looking into the tubes with a black screen I could see the slight flicker of the AKB correcting things.

Then switched AKB off and the flicker stopped and brightness settled OK, but I guess in time it'll drift off again.

So the problem is still present. Would next thing to try be replacing the video and gain boards or would it be best to just replace all the cards in the cage at once?

Thanks.
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draganm




Joined: 08 Mar 2006
Posts: 8990
Location: Colorado


PostLink    Posted: Sun Mar 19, 2017 7:50 pm    Post subject: Reply with quote

cynix wrote:
So the problem is still present. Would next thing to try be replacing the video and gain boards or would it be best to just replace all the cards in the cage at once?

Thanks.
generally, replacing a bunch of modules all at once is never a good idea with electronics. One at a time is the only way to know if your solving problems, curing them, or (since your installing old boards) adding new ones.

Best bet is to find a working chassis and buy it complete. Or, send your suspect boards to Curt for testing
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gjaky




Joined: 05 Jun 2010
Posts: 2789
Location: Budapest, Hungary


PostLink    Posted: Sun Mar 19, 2017 8:21 pm    Post subject: Reply with quote

cynix wrote:
Finally got a chance to play with this today.

I reseated cables and the moome hdmi board, then marked, adjusted back/forward and reset the pots on the video board and on the gain board. Also reseated the daughter card while I had the moome card out, which I hadn't done before, so all cards have now been removed and refitted.

Switched on and at first it looked perfect. Left it for about 10 minutes and then came back to check and the brightness had already drifted way too high, visible even on a bright screen and very obvious on a black screen.

Switched on AKB via menu and it immediately corrected itself and looked OK again. Looking into the tubes with a black screen I could see the slight flicker of the AKB correcting things.

Then switched AKB off and the flicker stopped and brightness settled OK, but I guess in time it'll drift off again.

So the problem is still present. Would next thing to try be replacing the video and gain boards or would it be best to just replace all the cards in the cage at once?

Thanks.


I think there is an interconnect coax cable between GAIN CTL and VIDEO OUT board, try to unplug to see if the brightness variation still occurs with AKB switched off. If it is still acting up you can rule out GAIN CTL board

_________________
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, VIM-DB
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Sun Mar 19, 2017 8:36 pm    Post subject: Reply with quote

gjaky wrote:
I think there is an interconnect coax cable between GAIN CTL and VIDEO OUT board, try to unplug to see if the brightness variation still occurs with AKB switched off. If it is still acting up you can rule out GAIN CTL board


I unplugged the cable between the GAIN and VIDEO boards but don't get any video display at all then. It still seems to sync OK and the OSD still works but the built in test patterns don't work and nothing from the video inputs.

Brightness level seems extremely low like that, can't see anything looking into the tubes at all, unless some text from OSD is displayed.
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Sun Mar 19, 2017 8:40 pm    Post subject: Reply with quote

draganm wrote:
Best bet is to find a working chassis and buy it complete. Or, send your suspect boards to Curt for testing


Unfortunately I can't seem to find a working XG135 with good tubes anywhere, otherwise I'd buy the complete unit and keep my own for spares.

It was Curt who suggested replacing all the boards in the card cage, but if I was doing that then I'd probably replace all boards together at first just to confirm that the problem is indeed on one of them, and then switch my original ones back in one at a time to find the exact source of the problem.
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gjaky




Joined: 05 Jun 2010
Posts: 2789
Location: Budapest, Hungary


PostLink    Posted: Sun Mar 19, 2017 8:40 pm    Post subject: Reply with quote

cynix wrote:
gjaky wrote:
I think there is an interconnect coax cable between GAIN CTL and VIDEO OUT board, try to unplug to see if the brightness variation still occurs with AKB switched off. If it is still acting up you can rule out GAIN CTL board


I unplugged the cable between the GAIN and VIDEO boards but don't get any video display at all then. It still seems to sync OK and the OSD still works but the built in test patterns don't work and nothing from the video inputs.

Brightness level seems extremely low like that, can't see anything looking into the tubes at all, unless some text from OSD is displayed.


That is how it should be, but let's see how the brightness stabilizes with a little longer with it, leave a menu displayed for a while...

_________________
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, VIM-DB
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Sun Mar 19, 2017 8:54 pm    Post subject: Reply with quote

gjaky wrote:
That is how it should be, but let's see how the brightness stabilizes with a little longer with it, leave a menu displayed for a while...


Ah, OK, thanks.

Pressing the "PIC FUNC" button to go into brightness/contrast adjustment (and thus enabling AKB) causes the brightness to go very high, lighting up the entire raster, but switching completely off and back on again has brought it back to normal with black screen, so I'll leave it for a while and see what happens.

Thanks again for your help. Smile
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Mon Mar 20, 2017 8:23 pm    Post subject: Reply with quote

After a little while the OSD disappears and leaves just the (very) black screen. I've left it running like that for a while last night and again today but so far the brightness appears to be OK.

At this point I think it's worth swapping out the video and gain boards for a start.

Curt, are you able to find a matching pair to replace mine?

VIDEO OUT = PWC-4062 , 72140621, Run # 2R4-16XPA1
GAIN CTL = PWC-4061 , 72140611, Run # 2R4-16XKE

Thanks.
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gjaky




Joined: 05 Jun 2010
Posts: 2789
Location: Budapest, Hungary


PostLink    Posted: Mon Mar 20, 2017 8:34 pm    Post subject: Reply with quote

I think the newer GAIN CTL boards are backwards compatible, if you fail to find the exact board.
BTW, have you played with the Test/Norm switch on the VIDEO OUT? Also worth a try.

_________________
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, VIM-DB
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Mon Apr 03, 2017 7:03 pm    Post subject: Reply with quote

It turns out Curt only has a spare Gain CTL board (PWC-4061) so if anyone has a spare Video OUT board (PWC-4062 , 72140621) for an XG135 or has any ideas on where I might obtain one, please let me know.

Thanks.
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Mon Jun 05, 2017 10:06 pm    Post subject: Reply with quote

I got the replacement Gain control board from Curt but unfortunately the brightness problem is still there.

So still looking for a Video OUT board (PWC-4062) if anyone knows of where one could be located.

Thanks.
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cynix




Joined: 12 Oct 2009
Posts: 39
Location: Scotland


PostLink    Posted: Fri Aug 25, 2017 10:13 pm    Post subject: Reply with quote

Curt managed to get me a video out board (PWC-4062) but unfortunately it didn't help either.

Someone mentioned it could also be the G2 controls on the HV PWB , so before I give up on this XG135 would it be worth trying to replace the HV PWB as well? What about the main PSU, any chance it could be that? Just thinking of other parts which are relatively easy to swap out.

Thanks.
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