Need CTC169 Expert

[MarkC]

Just got done solving a vertical jitter problem on a CTC169CL5 but now I
need to solve a vertical centering problem. It is just slightly out of
aliginment but when I adjust the vertical height for a full CNN (cable
news) ticker display (at the bottom of the screen) then the top comes
down too much. I cannot find any adjustments to center the vertical (no
service menu on this one). Do you know what parts would affect the
V-Centering? The parts I replaced are: C4520, C4503, C2313 (used a 220uf
to replace the odd 180uf), U4501 & CR4504. Thanks for any help,
Mark

 

[RonKZ650]

I've seen C4504 cause height and centering problems. It's a 0.47uf 100v.
Good luck,

 

[Jason D.]

On Wed, 31 Mar 2004 17:18:49 -0600 (CST), markcharles@webtv.net
(MarkC) wrote:

Just got done solving a vertical jitter problem on a CTC169CL5 but now I
need to solve a vertical centering problem. It is just slightly out of
aliginment but when I adjust the vertical height for a full CNN (cable
news) ticker display (at the bottom of the screen) then the top comes
down too much. I cannot find any adjustments to center the vertical (no
service menu on this one). Do you know what parts would affect the
V-Centering? The parts I replaced are: C4520, C4503, C2313 (used a
220uf
to replace the odd 180uf), U4501 & CR4504. Thanks for any help,
Mark

Insufficient height usually is the bad height pot and it's associated
circuit, any diodes (those little glass ones 1N4148, check their drops
while running), zeners for cutting off pulses feeding to the R/C
circuit to generate ramps for the op-amp IC).

The retrace from bottom to top is done with SCR transistor full on so
there is NO retrace cap like in any inefficient linear-based vertical
stuff depends on. During ramping (scan), the SCR is chopping in
decreasing ampititudes based on both horizontal rate and vertical rate
ramps to the IC.

Get correct cap for the 180uF, RCA still supplies parts for 169'ers.

Cheers,

Wizard

 

[MarkC]

I found out that the problem was caused by me when I replaced C4503 with
a 2,200uf cap instead of the called for 1,500uf. Some 169's use a
2,200uf but not this model.