Tech-Master NIB TV Kit #5516 - Page 20 - Videokarma.org TV - Video

Kevin Kuehn · #**286** 01-06-2017, 10:48 AM

It does seem more common to not have enough width. I suppose you could experiment with a 50 degree yoke, but hard telling what that will do to linearity and high voltage. Overall you have a very successful project.

dieseljeep · #**287** 01-06-2017, 10:52 AM

I went through most of the pages and noticed the set uses a width coil, but don't remember reading that you tried to adjust it. It does affect the tune of the flyback. It's amazing, that there is excessive width using a 21" CRT on a low B+ chassis.

Crist Rigott · #**288** 01-06-2017, 11:05 AM

Quote:

Originally Posted by Kevin Kuehn

It does seem more common to not have enough width. I suppose you could experiment with a 50 degree yoke, but hard telling what that will do to linearity and high voltage. Overall you have a very successful project.

Kevin,
Yeah, I thought of substituting the yoke.

Another though I had was seeing if I can find a 90 degree CRT instead of the 70 degree that I have now. These were just some thoughts I had but I never followed up on.

Thanks. I am pleased on how it turned out.

Crist Rigott · #**289** 01-06-2017, 11:07 AM

Quote:

Originally Posted by dieseljeep

I went through most of the pages and noticed the set uses a width coil, but don't remember reading that you tried to adjust it. It does affect the tune of the flyback. It's amazing, that there is excessive width using a 21" CRT on a low B+ chassis.

Like most width coils, there isn't much change when adjusting them. I adjusted the coil to the most minimum width.

Electronic M · #**290** 01-06-2017, 11:21 AM

Might help to re-tune that coil for max HV with the sleeve now installed.

Remember it was not uncommon to have 2-4" per side of overscan in sets of that size back then....Line voltages varied a LOT (and could be freaky low on farms), and the programming content lacked indicators of over-scan (so consumers would always complain of underscan, but never notice overscan).

Kevin Kuehn · #**291** 01-06-2017, 11:42 AM

What I'd prefer to see is a test pattern on the screen that was intended for a 4:3 aspect ratio display.

Crist Rigott · #**292** 01-06-2017, 03:05 PM

Quote:

Originally Posted by Kevin Kuehn

What I'd prefer to see is a test pattern on the screen that was intended for a 4:3 aspect ratio display.

Preparing a new HD 4:3 Indian Head Test Pattern DVD. Will post a picture when I have it ready and playing.

Crist Rigott · #**293** 01-06-2017, 06:22 PM

Kevin,
Here is a 4:3 Test Pattern without the sleeve:

Here is a 4:3 Test Pattern with the sleeve:

Kevin Kuehn · #**294** 01-07-2017, 12:36 AM

Boy that first picture is so close to being good. What happens if you slide the yoke back just a hair?

Findm-Keepm · #**295** 01-07-2017, 06:44 AM

Conventional wisdom for underscan is to add capacity to the yoke (or across the damper with a "cookie" cap) - perhaps reduce the cap value in the yoke? Most are 24-68pf in parallel with one horiz winding.

Cookie Cap:http://www.videokarma.org/showpost.p...5&postcount=10 (and no, I don't have one anymore)

Likewise, how about the feedback cap from on side of the width coil to the HOT - reduce it by a factor of 1/10th?

Just my thoughts....

dieseljeep · #**296** 01-07-2017, 09:58 AM

Quote:

Originally Posted by Findm-Keepm

Conventional wisdom for underscan is to add capacity to the yoke (or across the damper with a "cookie" cap) - perhaps reduce the cap value in the yoke? Most are 24-68pf in parallel with one horiz winding.

Cookie Cap:http://www.videokarma.org/showpost.p...5&postcount=10 (and no, I don't have one anymore)

Likewise, how about the feedback cap from on side of the width coil to the HOT - reduce it by a factor of 1/10th?

Just my thoughts....

I would leave it, the way it looks with the circle almost perfectly round.
Using a different yoke would affect the flyback action because of an impedance mismatch.

Electronic M · #**297** 01-07-2017, 10:15 AM

I think the first pattern is fine. You've got left side underscan in the second....Granted you might be able to fix it in the second by adjusting the centering.

Some overscan is the natural state of the design, I'd keep the overscan to look authentic....Plus unless you grossly underscan on all sides you are going to cutoff parts of network logos, news tickers, and sports score boxes....Programming directors now squeeze those things into the very corners assuming every viewer has a flatpanel set...

Kevin Kuehn · #**298** 01-07-2017, 10:25 AM

What I see is a small amount of un-linearity(stretch) on the left side of the picture without the sleeve, also a little stretch in the vertical at the top. I think if those could be eliminated the width and overall symmetry would be almost perfect. But it's so close the way it is.

Kevin Kuehn · #**299** 01-07-2017, 10:41 AM

Or maybe the bottom vertical is compressed? Regardless when you adjust the vertical linearity those two(top to bottom ratio) tend to equalize.

Crist Rigott · #**300** 01-07-2017, 11:28 AM

Wow, guys. I appreciate the comments.

I'll work on getting the picture where it should be without the sleeve.

I was playing with it last night some and it seemed that with the sleeve, the test pattern was straighter. In other words, the vertical lines were straighter than without the sleeve.

Just a note here. The sleeve seems to "compress" the whole picture, thus it fits into the viewing area of the CRT. It does not cutoff any portion of the picture.

I'll spend some time tweaking the picture to see what I can get without the sleeve and post the results here.

I did consider that maybe changing some cap might be an improvement.