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Discussion Starter · #1 ·
I ran across yet another XG with really crappy corner focus. The center focus control worked as it was supposed to, the edge control had no effect, and I simply could not get the corners to focus anywhere near close enough.


The set had what I call a 'sine wave focus' with the trimpots in the card cage, you could get the center focus to come in nicely, then the edges and corners would be out. If you detuned/defocused the middle, then both L and R edges would come into focus, so I knew this was an electronic problem and not a mechanical alignment.


Once again I found the STK 392-220 chip to be bad. Unlike the older PG models, there's no error code on the back when these chips go, and when I desoldered the focus chip, none of the pins fell out like they usually do on the PG projectors.


I'm going to suggest that any >5K chassis hour XG's get their STK chips changed. I've had enough failures now that I don't want to risk this in the field. I'll be changing them on all the ones I sell from now on.


Just FYI.


Curt


PS: THese chips are sometimes hard to find...they're also tougher to change than in the PG's both in accessing the F board and in the desoldering method, so if you're not a good solderer, do not try this at home.
 

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Curt,


were these focus tips Guy gave you 'proprietary' or general knowledge stuff? Would love to know....


WRT the STK's, I have recently retubed XG with 5300 chassis hours, but am in OZ. would it really be that difficult to do this proceedure? Should I not bother unitl/if the corner focus goes? Should I get the chips and hold in my 'glory box' until needed?


Adam
 

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Well what do you know, all of a sudden there's alot of talk about poor focus. There is three threads running right now talking about this on the XG's 9PG's and 10PG (mine).


Curt you are saying to replace the STK chips on the XG's with over 5,000 hours. Is that just on the F-drive boards? Does this apply to the 9PG's, 10PG's, with over 5,000 hours. What about my 10PG, it's having the same problems you are describing in this thread.


The chip I have is the STK392-040 on the F-drive. From what you are saying I should replace it, even if it is not the problem.


Deron.
 

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Discussion Starter · #4 ·
The procedures that Guy taught me are outlined in the 'hocus focus' thread, but seeing how it's done first hand is better than anything printed for me. I'm one of those guys that learns much better with hands on experience than reading an owner's manual..;)


If yor XG or PG set is working fine, and you can read the 'H' test pattern all over the screen, I'd leave well enough alone. If you just cannot get edge or corner focus and you know how to set the CPC magnets, focus and astig adjustments, then chances are you have a bad chip.


I've seen enough of these to make it policy to change these chips a s a precaution on >5K hour chassis that I sell. It will save a lot of hassle warranty-wise down the road (and hey, reassurance that you have several new chips in a newly purchased set from me is not a bad thing).


For the small change you have to spend to buy a set of spare chips, it might not be a bad idea to buy spares now 'just in case'.


Again, for people not up on their soldering skills, diving into a perfectly working NEC projector is probably a bad idea.


Curt
 

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Discussion Starter · #7 ·
Do a search on the net for the chip, they are out there.


The Marquees use a totally different convergence and focusing circuit, they do not use STK chips. This is good and bad, the Marquees do not seem to fail as often, but are harder to repair.


Curt
 

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Curt,


Are these the same STK's that can cause faulty/drifting convergence? Also, is this a service you are going to offer if we send you the boards?


Thanks.

Gary
 

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Discussion Starter · #10 ·
I will be able to change out the STK chips for those that are interested, let me get a bunch more in and I'll repost.


Yes, those chips can cause convergeence drift as well.



Thanks!


Curt
 

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I ordered the chip (STK392-040) out of a merchant here in San Diego, it's in stock in a Los Angeles wharehouse. It cost me $30.00. The place in San Diego is Willy's Electronics 619-477-2119, not sure if they deal with mail order. They said I should get it in at least 3 days.


Deron.
 

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Well that sucks you have to use Paypal, I would rather chew my arm off then use Paypal, less painful.


There is also a $6.99 shipping and handling charge, not sure if there is a minimun order, does not look like it.


Deron.
 

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Curt, I think I have the same prob w/ my XG. It has 6000 hours. I'm a newbie, so I haven't set the CPC magnets (yet), therefore I didn't post anything asking for advice. I have set the astig the best I could though.


What your describing is exactly what's going on w/ mine. Either center focuses great and edges are a bit off, or the center is slightly off and the L and R edges are perfect. Edge focus controls have little effect, and corner focus controls have no effect whatsoever. How difficult is it to change these chips? My soldering skills are excellent.
 

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Hi Curt,


I suppose when the focus chips fail the focus would be about equally bad at different contrast settings ?


As I understand Deron has a problem with side focus at higher contrast settings only which I know very well and I'd expect to see problems with any contrast setting when the focus chips are defective.


Also, do these focus problems show up on all three tubes or is it possible to have problems only with one tube ?


Oliver
 
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