Retrace Lines on 1948 Admiral 20x1

[Unimatic1140]

Hi everybody, I am in the process restoring my second vintage television set which is a 1948 10" Bakelite Admiral set. This is the same set as seen Rob's first post under the "Show us your vintage B&W sets!" thread. Its chassis 20x1, I recently found a brand new 10BP4 picture tube for the set and it is now has a wonderfully bright picture.

I have recapped the entire set and have cleared up most problems, including a troublesome sound issue that was cause by someone turning the Sound IF slug nearly all the way in at some point in this sets past. My one main issue with the set is I seem to have a problem with white diagonal retrace lines which appear generally on the top 1/2 of the screen, but at times can go almost to the bottom of the screen. On some stations I can get the lines to disappear, but during the momentary dark periods in-between commercials, I can still see these lines. In order for the retrace lines to completely disappear I need to turn the brightness control down to the point that the picture is too dark to be viewed comfortably. Does anyone know where in the circuit I would need to troubleshoot to try and minimize or completely remove the retrace lines?

Another interesting issue I have with the Admiral is when I turn the contrast control all the way down (counter-clockwise), I loose both picture and sound. I heard this was normal on some early receivers, but I sort of find that very strange that they would be designed with that flaw.

Anyway, thanks in advance, any help will certainly be appreciated.

Robert (Unimatic1140)
http://www.classicappliances.com