Dark Picture problem

[chipper]

I have a 57 Slyvania model 21T501 that I have done a total recap and good picture tube, but having problems with dark picture, contrast and brightness pot are also ok? Any help would be greatly appreciated. chip

[mstaton]

Hows the HV?

[Eric H]

Ion trap adjustment?

[chipper]

Ion Trap and H/V are good . I have done just about all the standard checks ?

[radiotvnut]

Did you check voltages on the CRT and video output stages?

[marty59]

Did you adjust the AGC for minimum gain? Even with a reduction in video the raster may brighten up some.

[chipper]

HEY: It was the plate resistor (1.2 meg) for the 12BY7 video output, had increased to 2.3meg. Now getting an ok picture .thanks