CurtPalme.com Home Theater Forum

[Ironman1965]

Have a NEC XG1350 PJ with mild text burn on green tube. Just bought a mint P16LJE08HKA tube and need the info for the resistor modification. Thanks in advance.

[Mark_A_W]

I disconnected the end of the resistor that goes from the K-H Pin connections on the neckboard to ground.

I'm sorry I don't have a picture and Mike P has my spares. The service manual diagram is wrong in this area and is useless, but the resistor is easy to find.


HOWEVER. My XG has an issue where the B and G tubes start out with too high black level and then return to normal as it warms. So I run the warmup screen at 5 minutes, and it's ok. And yes, the B and G tubes are the 08's, while the perfectly behaved R tube is an 07.


A friend fitted a 08 tube without any mods and it worked. I don't know if it has warmup issues. I just didn't like the idea of the G1 or G2 grid (I forget which) being grounded though a 3M3 resistor when it's not supposed to.


Mark

[Ironman1965]

Thanks for the response Mark. I was actualy doing some investigation into this yesterday, as I found a thread with a little more detail on the mod. I think I found the correct resistor. Was looking through XG schematic manual, and neckboard image has a resistor (Parts list identifies a 3M9 as R7946G) on HK pin that appears to go to a block on neckboard that is gnd'd with a 47ohm and 0.1uf in series. HK circuit doesn't seem to appear in schematic though. The 47ohm and 0.1uf also appear to supply the path to gnd for the G1, G2 and K pins spark gaps. What you're saying is to just disconnect one end of this resistor (R7946G) entirely then? I'm no electronics wiz (just know enough to be dangerous) so does any of this sound correct? This tube should be arriving in the next week or so. Comes with all HW attached to tube (neckboard magets and coils). I guess I'll have to re&re all this hardware as well (unsure as to what PJ it was pulled from)? Any tricks or warnings I should be aware of? Also are there any multimeter tests that can be perfomed on the raw tube to test for condition (just to save lowering and dismantling my PJ just to find tube is NFG)? If all goes well and I don't blow anything up , I'll post images upon completion

Here are the board images from the schematic manual

http://i154.photobucket.com/albums/s254/Ironman1965/Board1a.jpg

http://i154.photobucket.com/albums/s254/Ironman1965/Board2a.jpg

[Mark_A_W]

Yep, that's the one, R7946G.


But like I said, my 08 tubes take a long time for the black level to come good.

[Ironman1965]

Any Idea as to why this warmup is needed? Do you know anyone else who has a warm up issue? Could it be due to the lifted resistor? What is the difference in the 08 to 07 that you don't like the KH pin grounded through this resistor? Oops... Sorry for the bombardment of questions. Guess I'm not feeling dangerous enough. Thanks for the help Mark.