Gerbrand
Joined: 13 May 2008
Posts: 199
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| Posted: Sun Jan 22, 2012 11:36 am Post subject: Retubing a 1209s from PT22-22 to P19LUG/LPB: neckboard MOD? |
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Hello,
I retubed my BG1209s last year from PT22-22 to a mix of P19LUG and P19LPB.
I am having some issues with the brightness of my blue tube, which after a couple of hours of operation suddenly goes up.
While doing some research I found that some people say it is required to mod the neckboard when installing a P19LUG because of the extra grid. Other people say that it is not necessary, only that the grid is not used in a BG1209s.
The tubes have good focus, which some people state can be affected. However, I also found stories about G2 issues if you do not mod the neckboard (=connect KH to ground). If this is true, this could explain the blue issue.
So, does anybody know the definitive answer to this?
Cheers,
Gerbrand
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BG1209s (color filtered,new LUGs!), 13000h
Bat cave
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Mon Jan 23, 2012 7:49 am Post subject: |
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Hi,
I recently modified a Marquee neck board for using it with a LUG tube and went with the Sony G90 variant. I rerouted G2 to Pin 6 and mounted a 10Meg resistor from Pin 7 (KH) to ground. So far no issues even after several hours of testing. You might want to try this as it's cheap and easy to do.
I could imagine that leaving the KH grid floating would allow electrons to be deposited there. Maybe a specific amount of charge could then trigger the effect You're describing. On the other hand I wouldn't tie the KH grid to ground directly.
Of course Tom's opinion keeps valid and could in fact be the cause too.
Regards,
barclay66
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