The flagging is caused by Heathkit's implementation of the NTSC vertical blanking interval, which it apparently misinterpreted as the vertical sync pulse. The vertical sync pulse is thus excessively long, about 1.3mSec when it should be about 180 uSec. The original IG-28 Vsync period thus blanks a large number of horizontal sync pulses. Absent these, most modern TVs lose horizontal frequency lock and "wander" at the top of the picture. You can fashion a BJT monostable multivibrator using 2N3904 transistors to develop a shorter sync pulse. The monostable can be interposed by cutting the trace from the vertical sync shaper MC724 pin 3 and the sync mix MC724 pin 10.
Tnx for sharing...I miss those days, much better than today...
how exactly do you have this hooked up to the television?
Would you have a manual for the CD-1 colour bar and dot generator?
Unfortunately, no. I wasn't able to find available for download on the Internet either.
How do you eliminate the flagging vertical lines at the top of the picture. I built the add-on circuit for this but it didn't help.
The flagging is caused by Heathkit's implementation of the NTSC vertical blanking interval, which it apparently misinterpreted as the vertical sync pulse. The vertical sync pulse is thus excessively long, about 1.3mSec when it should be about 180 uSec. The original IG-28 Vsync period thus blanks a large number of horizontal sync pulses. Absent these, most modern TVs lose horizontal frequency lock and "wander" at the top of the picture. You can fashion a BJT monostable multivibrator using 2N3904 transistors to develop a shorter sync pulse. The monostable can be interposed by cutting the trace from the vertical sync shaper MC724 pin 3 and the sync mix MC724 pin 10.
Is that cap burned at 10:30?
+Jordan Rubin No, it was lit from above and that is just a shadow cast by the cap above it.
does it actually work on ch 2-6? or does it only work on 3/4?
I can output at any frequency from channel 2 through 6.
thank you.