Re: Significantly drop G2/brightness (4600 raster hack)?

From: John Robertson <jrr_at_flippers.com>
Date: Mon Dec 23 2002 - 12:52:47 EST

Any risk of excess cathode current flow if the grid is shorted to ground?
I'm thinking that this might stress the picture tube too much. BUT I am
definitely not a picture tube expert.

John :-#)#

At 12:38 AM 23/12/2002 -0600, Rodger Boots wrote:

>Gregg Woodcock wrote:
>
>>OK, here is a very interesting udpate.
>>By putting increased resistance, I was able to drop the previously lowest
>>(stock/non-modified) G2 of 375V to about 200V with not a bit of difference
>>in brightness. Well I figured I'd show the macine who was boss so I shorted
>>the G2 pin to ground (0V). I got a picture that was about half as bright as
>>it should have been to be perfect. What is up with THAT? I got roughly the
>>same brightness with it ungrounded. I am going to use the rejuvenator to
>>check for G2 short in the tube but as I recall, I backed this one up to
>>another machine that was working fine and it proved without a doubt that the
>>tube was fine (95% sure about that). I must have some kind of a ground
>>problem but I just don't see how/where...
>>
>
>
>If running G2 grounded still gives a fairly bright picture you have either
>too high high voltage or not enough cathode to grid 1 bias.
>
>Since dropping G2 to ground DOES get the brightness low enough you might
>just add a second resistor from G2 to ground to whatever resistance you
>already have from G2 to the screen pot so the effective voltage range of
>the pot is where the CRT needs it. It's not going to hurt anything to run
>G2 near ground, but make sure the high voltage isn't excessive.
>
>
>
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Received on Mon Dec 23 09:54:27 2002

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