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NEC XG 135 Brightness problem
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cynix



Joined: 12 Oct 2009
Posts: 39
Location: Scotland

Posted: Wed Sep 27, 2017 8:00 pm    Post subject:

Apologies for the delay in updating.

I wasn't able to get the Picoscope working on the laptop I had access to and I've been busy finishing up working on my "hobby" car that I've had in bits since June, so not really done any more with the XG135.

I put the hush box back in place so I could actually watch some movies for the first time in months and with AKB enabled to "fix" the brightness drift and the normal brightness level reduced a couple of points to mask the slight flicker caused by the AKB corrections it's really still quite watchable.

I did notice that convergence is drifting off a little more than it used to , even between the 1 hour to 2 hour power on time frame it's drifting slightly (whereas it used to be pretty consistent after an initial 20-30 mins warmup), so maybe Curt was correct from the start and the problem is really just that the tubes are about done at 7K hours even though only the green is really showing the wear.

<edit> I did also remove and inspect + clean out the main PSU and it looked fine, no leaking or bulging caps or anything like that.
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gjaky



Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary

Posted: Thu Sep 28, 2017 10:01 am    Post subject:

All tubes at the same time and for the same extent? Very unlikely...
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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, VIM-DB
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Curt Palme
CRT Tech


Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC

TV/Projector: All of them!

Posted: Thu Sep 28, 2017 2:00 pm    Post subject:

How much air flow is in your hushbox? XGs run hot to start with, and I've seen people completely encase XGs with zero ventilation.. and wonder why the projector failed... repeatedly. (Ok, that was ONE client, but I've never been a 'fan' (pun intended) of them.)


gjaky, my suspicion is that one tube is making a mess of the AKB circuit, causing the brightness issues. I've seen this in a couple of Barco 1209 as well.
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cynix



Joined: 12 Oct 2009
Posts: 39
Location: Scotland

Posted: Sun Oct 01, 2017 10:21 pm    Post subject:

Plenty of airflow through the hushbox, via 2 bathroom type extractor fans running through a big variac to slow them down to reduce the noise.

Pic of the install from the floor above:



Case of the projector is removed to aid cooling and I tested it with 2 temp sensors (one on the big heatsink on the top above the tubes and one at the back at card cage) to set the fan speed as quiet as possible while keeping the temps slightly lower than they were with the case on and projector not in the hushbox.


It's ran OK like that for more than 10 years before this problem appeared so I don't think it's related, but all components are over 20 years old now so who knows.
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