Classic II display not drawing across full screen

[bpetersen]

See attached photo. I tuned it with the seven pots as best I could. It has been cleaned, recapped both boards, etc (separate thread on that) to get this far.

Is anyone familiar with this problem? Without knowing what I am talking about, it feels like it isn’t scanning all the way across. Maybe a problem in the h scan area of the AB??

Secondary problem is it is quite dim.

Third problem is that it feels like it is not focusing. Would others agree with that?

Any advice on next steps is appreciated.

 

[bpetersen]

Here is the oscilloscope output at the deflection yoke for vertical and horizontal. Does anyone have correct traces I could compare to? Or feedback on whether this is clearly bad or not?

 

[makkuss2000]

Here is the oscilloscope output at the deflection yoke for vertical and horizontal. Does anyone have correct traces I could compare to? Or feedback on whether this is clearly bad or not?

There is a problem on pin 3 (if figure 2 is referred on pin3). You should have a different frequency and a different wave too (60.15 hz). Did you still changed the TEA ic?

 

[bpetersen]

Figure 2 is a zoom in of figure 1. Figure 3 is the 60 hz signal. I didn’t take a screenshot of the second 60 hz signal but i can do that.

 

[bpetersen]

Fixed! It was a bad QL2. I had already replaced it twice with parts I got on eBay. Replacing with a Mouser part completely solved the problem. Other than the floppy, everything works now.

If others have bad analog boards, I’d be happy to debug and fix them. I have so much hard won experience now, it would be nice to use it.