TV Color Generator Problem

[Krankshaft]

I recently came into posession of a B&K 1245 Color Generator.



So I hook the RF output to a 300 to 75 ohm matching transformer. Yes it's that old what is twinlead again ?

Everything looked good the color bars and the dot pattern but the vertical lines have a jittering problem.

You can really see it in the crosshatch pattern.

So I check the alignment of the countdown circuits with my scope everythings spot on.

So on a whim I try it on an older GE TV made around 1981 or so and the vertical lines are now solid.

Is there some variable in more modern TVs that is causing the vertical line jitter?

[Wizard]

Re: TV Color Generator Problem

This is EXACTLY what macrovision works off this.

Copyholders asked the TV makers to desensitive the lock in speed on TVs while leaving the sensitivity in VCRs high so it keep chasing the timings causing pic to go wavy/fading in and out on playback.

Cheers, Wizard

[Krankshaft]

Re: TV Color Generator Problem

So it's a lock problem then V sync would be responsible for this right?

I say that because the horizontal lines are straight.

How do modern generators overcome this?

Are there any types of circuit modifications that could remedy this?

[i4004]

Re: TV Color Generator Problem

>How do modern generators overcome this?

by being more precise?

btw. no, not v-sync, but h-sync...
you have lines being shifted to left and right at certain places, which means h-sync is off...
ie it's left-right distortion, not top-bottom...

top-bottom(vertical sync) distortion would make some horizontal lines thicker, and squares would become rectangle etc.

[Krankshaft]

Re: TV Color Generator Problem

I thought I messed up on which sync signal it was.

So the beam is being pulled down at the proper rate however the horizontal sync is causing the misalignment.

I have a newer model I'll be picking up sometime next week this one is IC driven a BK 1248 we'll see how it goes.

Like this:

http://cgi.ebay.com/CL-6012-B-K-PREC...3A1%7C294%3A50

About 9 patterns and a video and sync output my fingers are crossed on this one.

[Toasty]

Re: TV Color Generator Problem

I have the 1248 and it doesn't produce that distortion. And you can connect without the balun.

Toast

[Krankshaft]

Re: TV Color Generator Problem

Whew that's a relief thanks for the update on the 1248.

The 1245 is all discrete components while the 1248 has more patterns and IMO looks alot nicer.

I got the 1245 for free so I thought why not.