Jerry,
you welcome. I see you probably used R186 trig bal to adjust voltage. that -3V
was probably coming from out of Q190.
good job,
Greg
At 08:24 AM 2/5/07 -0800, Jerry Massengale wrote:
Greg,
Thanks for your good suggestion. The signal at the input of the trigger
generator looked great and I assumed the balance circuits was okay. I
checked
the adjustment for trigger balance and found that the junction of r200/c200
was at -3V rather than +65mv. I adjusted for the +65mv and it syncs very
good
now. I should have checked the external sync too.
Thanks for your good help.
Jerry
Greg_A <<mailto:greg.a%40dslextreme.com>greg.a@...> wrote:
Jerry hi,
I looked for you schematics and I think you could concentrate on signal flow
from Q184, Q190 up until U200 pin #15 - that should be trigger in for that
chip.
Greg
At 07:13 AM 2/4/07 -0800, you wrote:
Greetings,
I have an SC501 that has poor sync. The unit works better at Usec settings
than Millisec settings. I can swap U200 with a unit that works good and see
no improvement. I can set 2 units side by side on extenders and compare
voltages and waveforms and not see anything suspicously different between
the
two. One is stable and locked, the other is very, very, close but not
stable.
When the sync on the bad unit is at it's most stable point, the blanking
output slows dramatically and the screen flickers.
The power supply voltages are good with no apparent ripple. The Msec timing
cap, C230 measures the same on both units(0.987uf and 1.02uf).
I am attaching the schematic for the U200 circuit. Suggestions are
welcome. I
would love to see a datasheet for U200. It is a Tektronix made IC, pn
0155-0055-00.
Jerry
Emacs!
