How to find Gain pot


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How to find Gain pot

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Gnarvster
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May 2, 2005, 2:10 PM

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How to find Gain pot	Can't Post

Hello!

This is my first post, glad to be here!

I recently bought an old crt projector, a Thomson/Nordmende TVP-100. The projector is in good shape, but i need to balance out gain between the 3 guns. The green gain is set too high, causing blooming, and varying focus on the green gun, as well as bad greyscale. (white top is greenish)

I have found focus and G2 settings for each gun on the crt neckboard, but i have not been able to find any gain settings. There is one more pot on each crt neckboard, besides focus and G2. The pot has three legs and is marked PK01. Adjusting it gives no visual effect that i can notice.

If anyone could give me any hints on where to start looking for gain settings I'd really appreciate it, since i have not been able to find a service manual for the projector.

If You think gain setting is the wrong way to go here, please suggest other settings. The other guns seem to cut off the top earlier than the green gun, but i do not know what setting adjusts the overall "max" voltage per gun. Perhaps lowering this max would make the green gun not overexpose so easily. This is my second hypothesis ;)

As i said above, any help greatly appreciated!

best regards
Joachim

shadetree
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May 5, 2005, 6:14 PM

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Re: [Gnarvster] How to find Gain pot [In reply to]	Can't Post

the g2 ajustments are your gain adjustments

Gnarvster
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May 5, 2005, 10:54 PM

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Re: [shadetree] How to find Gain pot [In reply to]	Can't Post

Oh, I thought G2 was screen, ie black-level! Perhaps I've misunderstood something. Or perhaps I didn't explain right. What i was looking for was Green video gain, or green drive. Which G2 doesn't seem to do.

Unimpressed

shadetree
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May 5, 2005, 11:22 PM

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Re: [Gnarvster] How to find Gain pot [In reply to]	Can't Post

sounds like you have a very weak crt

Gnarvster
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May 5, 2005, 11:41 PM

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Re: [shadetree] How to find Gain pot [In reply to]	Can't Post

I guess the CRT is pretty old, but since it seems to "overdrive" like this i suppose a gain adjustment would make it better.

Am I right?

With slightly lowered contrast and a better video signal (rgb) the problem is not that serious. If this was a normal monitor, not a projector, I'd just lower green gain somewhat, as that normally would fix or at least mask the problem. My problem now is I have no service manual, and cannot find the gain settings. I think they should be on the video neckboard, but no.

I need a service manual or a schematic to find the gain pot. Again, not the G2, as this is most definately black level control. At least it certainly seems to act that way

(This post was edited by Gnarvster on May 5, 2005, 11:43 PM)

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