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Discussion Starter · #1 ·
I need some advise on diagnosing a problem with my NEC 9PG. It has been working flawlessly for the past two years. It recently developed a problem with the convergence. When I start the unit up the picture looks fine for about a minute. The red portion of the image starts to drift. The unit is setup as a tabletop front projector. The red shifts upward and to the left by about 4 inches on a diplay area of approximately 8 feet diagonally. On the right side the image is slightly down and to the left. When I try to correct the convergence problem using the remote control , the red image can be adjusted vertically but not horizontally. The problem occurs with the same amount of distortion whether using composite video( NTSC), S-video or RBG at 1024*768. In a previous thread I saw a posssible fix as the replacement of the STK392-040. Could this resolve my problem. I did the initial setup of the unit and convergence so I feel comfortable in replacing parts as long as it does not involving soldering or elaborate test rigs. I have the Service manual and the Trouble shooting manual for the unit but could not see anything resembling my problem. I called a service company about fixing the unit and they want be to bring it to their shop. I would like to avoid this if possible.


I have a further question. On one the sites, http://www.snaggs.com/projector/disp...pagetitle=NEC, there is a hand drawn circuit diagram for an NEC PG fan modification. I read a response to a thread in this forum which made a passing reference to a fan mod and I was wondering about the benefits. Is necessary to modify all of the fans. The diagram does not provide a parts list. Is there a better version out there with a parts list.


I am new to this forum so I aplogize if this material has been answered previously. I had searched the site to see if I could find some answers. Any advise is much appreciated.

Thanks


Paul
 

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Sounds like the SDK chips on the C-drive board are failing. Do a search on this, you will find it's common and easy to fix. Do a search on SDK392-40

and you will need a soldering iron. It is very simple, though.


The fan mod? Well, there are different ways to go about it. Because the SDK 392-40 chips run so hot, I would only slow down the one fan under the cover. I slowed mine down using a 75ohm resistor in line with the red wire. This works for me, and I don't take responsibility if anyone else does this and fries their projector.


Marc
 

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Marc.. they are actually STK chips.. not SDK. And yes i agree that that is probably the cause of your problem. I would replace all 3 chips. 2 on the C-drive and 1 on the F-drive.
 

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Thanks Cookie, that's what I meant. He he... Braindead.


Marc
 

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For complete clarity, its the STK392-040 chips. They are a common chip and available from many sources, like http://www.datadart.com/ just put STK392-040 in the search box. The C-drive board stands up between the red and green tubes under the main DEF board. you can take the board out quite easily if you have a LONG phillips #2 screwdriver with a magnetic tip. I've had a tech repair these for me and he only took about 2 minutes to do a great job. He did, however, recommend adding another heat sink for the chips alone as they get very hot down there. The chips are quite large physically about an inch and a half wide and about two inches long. You'll see them quite easily on the bottom of the C-Drive.
 

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Discussion Starter · #6 ·
Thank you all for your advise.

I have put in an order for the replacement STK392-040 chips. I am glad it is a relatively simple fix.


Paul
 

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Soldering will be required to replace those chips. If your not confident in soldering, as per your original post, then i would suggest taking the circuit board and your replacement STK's to an electronics repair ship and get them to replace the chips for you for a small fee.


Or better yet find a friend who is confident doing it. :)
 

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Discussion Starter · #8 ·
While I am a klutz with a soldering iron, my brother is a wizard. I think I will bribe him into helping me.


Paul
 

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Make SURE you use new heatsink compound when you replace them for optimal heat tranfer.


Marc
 

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Yep good thinking. And don't get any of that stuff on your skin.. apparently its highly poisonous.
 
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