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Discussion Starter · #1 ·
Hello all...further adventures with the 6pg. Whoever said the learning curve is steep with this unit wasn't kidding. On to the problem: When I am trying to converge the red tube with the green, the horizontal amplitude and linearity controls for the red tube don't do anything. I can run the scale all the way from +100 to -100 and no change is seen. The vertical works fine and all other controls work fine for the red as well as the other tubes. I am guessing its a convergence board problem but am open to any suggestions. Thanks, Guy
 

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Discussion Starter · #2 ·
Further investigation shows that all my horizontal convergence adjustments for the red tube have no effect. Also, when I lift the main board to get to the red tube, the whole red image shifts a bit like I was twisting the red centering magnet (which is tightened properly) I hope this helps pinpoint the problem. Thanks, Guy
 

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Check the connections on the boards. Also, it is normal for the image to shift slightly when you move the board. If all the connections are OK, it will likely be the STK chip everyone raves about. It's not a big problem to replace, many here, as well as myself have had this problem.


Marc
 

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Discussion Starter · #4 ·
Thanks Tinman. I am assuming these are the boards on the very back of the tube? I can't seem to find a diagram naming each board in the unit. Also, where does one aquire this STK chip if that proves to be the problem. Thanks for the help, Guy
 

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Discussion Starter · #5 ·
OK. Its amazing how well the search works if you actually use it. I found the correct board with the stk chips. Looks like I need to pull the board, locate the chips locally (I read I should replace both), And find a tech to do the soldering for me. Does this cover it pretty much? Thanks, Guy
 

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GuyC, your projector has three STK392-040 chips. Two of these are located on the C-drive board (i believe one of these chips is your problem) and one is located on the F-drive board.


The c-drive and f-drive boards sit beside each other and are located between the green and red tubes.


If you are going to replace an STK chip on the c-drive than i would recommend replacing all three STK chips at the same time. They are notorious for failure once the hours have clocked up... most NEC owners will one day experience this fault.


Check out:
http://audiolab.home.mindspring.com/


They are selling STK392-040 chips for $15.00 each.


The chips are quite large and fairly easy to solder. If you have soldered before than you shouldn't have a problem. Otherwise just take the circuit boards and the chips to a local TV repair place and they will easily replace the chips for you for a small fee.


Folding down that board (deflection board) will cause the red convergance to shift. I have seen this happen on all PG series projectors. It is quite normal.
 

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On a side note: I have also sometimes found the large resistors on the same boards to open up. While this is rare, I had to replace 3 of them along with the STK chip. Really an easy procedure, actually. The resistors were 1.8 ohms at 2 watts, I believe. ( off the top of my head ) If you take the board out, you might want to just check them all with an ohm meter. If you cannot do this locally, there are several people here, including myself that can fix this board for you.


Marc
 

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Note, change it anyways if you want, but I have never had the STK chip go on the F board, but have had lots of bad C board chips...


Curt
 

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Hi Guys,

If you over heat a c-drive the heat transfer will go to the f-drive and vise-versa. The bottom of the projector is in fact a big heat sync. If this is ceiling mounted then all the heat will be transfered to the bottom plate and stabilize. This is what the normal warm up time is doing and why you wait 30-40 minutes before adjusting.


When you spend a lot of time doing corrections either focus or convergence just walk away from the projector for a bit to let it stabilize, I think you will find when you come back a slight change will occure, instead of over correcting let it rest and go have a cup of coffee.


This could save you money in the long run and with less drift, keep the bottom of the projector clean.


Im only mentioning this in an effort to save your boards from failure and to avoid the problem from the get go, all projectors are female. Doug
 

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Curt, I recently had to change the STK on the F-Drive board. I could get center but not edge focus. It also took out the associated resistor with that output. In fact, it burned that leg of the chip right through. I'll never know what caused it, or why the projector never shut down, but it's fixed now. I suppose it couldn't hurt to change all 3 chips. It's so simple.

At least the PG is designed to be serviced even hanging on the ceiling. Big plus.


Marc
 

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Discussion Starter · #11 ·
Wow, thanks for all the great responses. I love this forum. I know someone who does board level work so no problem there. I doubt I will have too much problem finding the chips in Dallas. With luck, I should have it going by Wednesday. I've got the middle 3 feet of the screen looking wonderful and I can't wait to see it edge to edge. Thanks again, Guy
 
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