TRS-80 Model 4 NGA Video Still has Scan Lines

[andydoty]

I've replaced the 500k video adjustment pot and still have lines. Has this happened to anyone else before? The camera is imposing the dark section on the picture, however, the scan lines are consistent. It's been sometime since I've delved into TRS-80's and used to sell them in the late 80's. Ah, the wonders of reliving your past...

 

[andydoty]

So, FreHD installed. Other than that those pesky lines... Any thoughts?

 

[Trash-Eighty]

Does turning the brightness wheel have any or no effect?

 

[andydoty]

Does turning the brightness wheel have any or no effect?

It does a little bit. And I did change it with a new POT from Mouser.

 

[Trash-Eighty]

ok - have you read this thread: Model 4 Screen Brightness Issue
I think you should check the voltages for the brightness from the tube's neck as stated there in post #12.
And check every part and solder joint that is on the brightness path for your specific video board (part no.) regarding to the schematics.
Be careful with the high voltages.