Problem Sanwa 29e31s green

[jerryspaghetti]

My monitor has too much green. There are red and blue gain pots on the neck board but can’t see a green pot. Is there one?

 

[tb2000]

Could be a problem on the neckboard or the chassis. You could try turning the other pots up to compensate, could be that those guns are getting a bit weak. Or find the green cutoff (should be one, I haven't looked at a 29e31s for quite a while though so not certain). What crt is it using? They used 2 or 3 different makes/models if I remember correctly.

 

[jerryspaghetti]

When I up the red and blue gain it starts bleeding. I can’t find a pot to adjust green gain at all.

 

[gunblade]

desolder the GK pin on the crt socket, if it remains green then you have a gun problem
there are 4 other pots on neck card - sub contrast, blue cut off, green cut off and red cut off

 

[jerryspaghetti]

desolder the GK pin on the crt socket, if it remains green then you have a gun problem
there are 4 other pots on neck card - sub contrast, blue cut off, green cut off and red cut off

Thanks, any images or schematic to show where or what the GK pin is?

So we're saying there is NO green gain adjustment pot on the neck board? Is it just me or is it strange that there's a blue and red gain but no green?

 

[gunblade]

many chassis don't a green gain
gk pin is marked on the neck card crt socket

 

[jerryspaghetti]

Thanks man

 

[jerryspaghetti]

Ok so there was a ‘KG’ pin marked on the neck board so figured that was it.

Desoldered it and green went leaving perfectly adjustable Red and Blue. Started purple, then red when I cut off blue and Blue when I cut off red.

I’m hoping this means that I just have a dodgy ‘Green bias’ pot on the neck board maybe?

All three Bias pots have been replaced with aftermarket ‘502’ pots by the look of it.

I REALLY want to rule out a knackered tube!

 

[gunblade]

if you obtained black and no green at all then tube likely ok

 

[jerryspaghetti]

if you obtained black and no green at all then tube likely ok

There was zero green as per those images and the Naomi logo was black. So you think I might be ok?

You reckon I should just replace the green pot maybe?

Pic below shows that they are replacements but are they the right K for job?

 

[gunblade]

swap blue and green pot if you think its that

 

[jerryspaghetti]

Will give it a try cheers

 

[jerryspaghetti]

They’re 5k pots and I have some spares so swapped the green one and no difference at all.

It’s like the green is just way too high by default and the only way to get the colours correct is to turn it completely off. Then everything is too dark and raising the contrast and brightness to lighten it causes the red and blue to bleed.

The neck board has a sub contrast, red green and blue bias pots and it also has red and blue gain pots only. Unless there’s any pots elsewhere for colour, then this can’t be solved by adjustment.

I can get really strong green, red and blue colours just can’t get them to work together to get a clean white. The white Naomi splash screen is a yellow colour.

I just want to rule out the tube as the problem before I spend money on chassis repairs

 

[Retroman839]

What about final resistor in the green circuit on the kneck board .
I had a lot of red on one chassi
Amd the final resister was visually over heated .. not saying I know how or why
The resistor would be over worked but
I kmow
I have a chassi with visable over heated
Resistor on the red and it’s swollen, and colour bands are discoloured from heat. Result is way to much red.

 

[gunblade]

disconnect video signal, increase screen volts on flyback so you obtain a raster - is it white or still green?

 

[jerryspaghetti]

disconnect video signal, increase screen volts on flyback so you obtain a raster - is it white or still green?

All green. Guess that’s bad….

 

[Retroman839]

Can this be a short on the green gun that can be removed ?( burned away)

 

[gunblade]

i don't think its tube, and now a odd signal issue has been ruled out
i think the issue will be a transistor or the ic on the neck card

 

[Retroman839]

bad transistor or ic
Will this cause overheating in a resistor ?
Making the resistor more open ?

 

[gunblade]

bad transistor or ic
Will this cause overheating in a resistor ?
Making the resistor more open ?

depends on chassis but i would say leaky drive transistor