Screen brightness decreases depending of the game stage

[copados33]

I have a monitor in one of the arcade machines that as the game screens change the brightness decreases, this only happens in some stages in different games, it doesn't matter what I use to play the game, be it the original PCB  or Mame, it happens for example in the Teenage Mutant Ninja Turtles in the intro scene before the turtles jump inside the building, the screen is fine but soon as the the game starts the screen turns darker.

Then when I enter the office where you fight the first boss the brightness returns to its original setting, the only solution I have until now is the brightness  potentiometer in the remote board all the time to make the image look as I want,

is there any way around this??, maybe moving the voltage potentiometer a bit on the monitor chassis? I ask for help from experts before trying anything that might damage the monitor.

[grantspain]

and the make/model of the monitor is?

[copados33]

It's 27" semi flat tube coupled with a Wei-ya universal chassis.

[grantspain]

is there a ABL adjustment on your new wei ya chassis

[copados33]

Excuse me but I don't know what ABL means, this one here:

[grantspain]

i doubt that has a ABL adjustment on it,
That is a cheap chassis,it is probably slightly out of spec for your tube

look up ABL on google

[copados33]

Australian Baseball League 

got it: "automatic brightness limiter"

[grantspain]

Australian Baseball League 

got it: "automatic brightness limiter"

you got it,
some old tubes are ok on this sort of chassis but later tubes do not like them-i believe it is to do with the ABL circuit