Macintosh Plus display woes

[Thebrann]

Can anyone help me out?

My Plus is stretching the screen beyond the upper and lower bounds of the display. Adjusting the height potentiometer will not adjust this back to its correct size. There is a little x axis jitter - about 2mm of deflection every couple seconds. Tapping the analog board does not cause this jitter so I don’t think it’s the solder joints.

The voltage is adjusted to 5.00 but the 12v is only showing 11.6. I don’t know if that’s too low.

I put a new U1 recently because my picture was collapsing into a horizontal line. After I installed it, this was the screen I saw. On the analog board I reflowed all the connector joints. I have no Rifa caps on the analog board. R2,3,and 4 were checked in the circuit and seem to be within spec.

Interestingly, if I adjust the 5 volt all the way down to its minimum (under 4.5), the screen is almost perfect (just can’t see the sides because they are over scanned off the edges of the screen on all sides).

Any ideas for me?

 

[3lectr1cPPC]

I'll bet it's something more than this, but have you replaced all the electrolytic caps? While I'd guess that something like this would have more than that at fault, it's always a good starting point as it will need to be done either way at some point.

 

[Thebrann]

Replaced C19
C20
C10
C6
C22
C23
C11
C5
C1
cr15, 3, 2, 4, 7, 8, 6

U1,2

Q3,4,5

Checked all these resistors but did not replace:
R30, 29, 28, 21, 31, 22, 10, 3, 2, 4, 58, 11, 6, 23, 24

Essentially I replaced every component in the vertical circuit. Except the resistors and q1 and q2

Worked for about 90 seconds but blew the tantalum c1 that I ordered. Replaced with the original c1 from a scrap parts board and it works now