Tech-Master NIB TV Kit #5516

[Electronic M]

Originally Posted by Crist Rigott

Tom,
Not sure what you mean by letter-boxed or pillar-boxed. The DTV does not have a zoom feature.

Maybe I can borrow another converter box.

https://en.wikipedia.org/wiki/Letterboxing_(filming)

[Crist Rigott]

Originally Posted by Electronic M

https://en.wikipedia.org/wiki/Letterboxing_(filming)

The test pattern is one I made from a hi res 4:3 pattern. I converted a jpg to a 30 minute movie and saved it to a DVD.

[Electronic M]

Originally Posted by Crist Rigott

The test pattern is one I made from a hi res 4:3 pattern. I converted a jpg to a 30 minute movie and saved it to a DVD.

There is enough variance in digital processing implementations that I can't comment based on that info as to whether your system generated a good pattern or not.

The best advice I can think of to confirm things is to connect another 4:3 display (such as a modern CRT set) that is known NOT to have excessive over scan to both signal sources in the same manner as your Tech-Master and see if there is a black bar wrapped around that test pattern, or if the DTV picture is excessively zoomed (I suspect one of those is occurring).

With changing aspect ratios and poorly standardized means of dealing with it flooding consumer and broadcast markets alike, there is good argument to keep a VCR or pre-2000 test pattern generator on hand...So you know you have a signal source that will always give you an accurate measure of over-scan...

Too many modern signal sources are capable of distorting things and giving a misleading signal.

[Kevin Kuehn]

Originally Posted by Crist Rigott

The test pattern is one I made from a hi res 4:3 pattern. I converted a jpg to a 30 minute movie and saved it to a DVD.

I'm guessing your digital TV signal is broadcast in wide screen format, don't you think? It does fill out the width on a modern wide screen set, no? But when you made your 4:3 aspect ratio test pattern DVD, the machine plays it back as it was originally formatted.

If you put your digital TV box in letterbox mode it should shrink the picture width down and put a black bar at the top and bottom, although I don't have such a device so I have no idea if they even have that feature these days.

[Eric H]

From this screen shot it looks like you have some pretty severe Horizontal linearity issues on the left side of the screen.

The "through the scope" shot here should be perfectly round, it's egg shaped with the point to the left of the screen, I also noticed all the credits were cut off on that side too.

As has been mentioned, it may just be a shortcoming of the sets design.

Is it adjustable so the stretch is equal on both sides? If you can do that you may then be able to reduce the width to bring it into a circle.

Oddly enough it doesn't look as bad with the test pattern.

[old_coot88]

Originally Posted by Eric H

Oddly enough it doesn't look as bad with the test pattern.

Yeah, the test pattern display was what threw me off too.

[Crist Rigott]

Here are a couple of pics with another TV next to it. I just used clip leads to connect the antenna inputs together. The other TV is a non-HD 9" RCA.

[Crist Rigott]

Well guys, I found the problem with the over scan using the converter for OTA programs. It was the zoom feature. I looked for the zoom feature in the instruction manual, but no mention of the word zoom. But I did find out how the "Picture Format" button works. One thing though, it works real well on other channels, but is very sporadic on MeTV!

With the format in "normal" I have black bars along the bottom and top of the picture. I'll but my video generator on it and adjust the linearity and I'll be done.

Thanks for hanging with me and all your suggestions.

[Electronic M]

DTV stations send signals that dictate format to the box. Some stations handle it better than others and some boxes give the user better control of format/zoom than others.

Glad you got to the bottom of it.

[Crist Rigott]

When watching TV, I have to have the "Contrast" 99% all the way up. I'm considering adding or taking away some resistance in the contrast circuit. Here is the schematic and the contrast when watching TV the resistance is almost all the way down and the wiper is moved closer to the tube.

I'm thinking of reducing the R53A from 1K to something like 680 ohms. Would this put the contrast control more off all the way? If not, what could be done.

BTW, the schematic shows the pot value as 2K, but the kit came with a 5K pot.

[old_coot88]

I would try a couple of things first. Run a jumper from the 12BY7 cathode (pin 1) to pins 3 & 9. See if contrast improves.

If it does*, check resistance from the wiper to the top lug of the contrast control when it's rotated to max contrast. It should be zero or near zero ohms. If it is, try shorting out the 39 ohm resistor R109. See if that gives more grunt.

*Be sure jumper is removed.

[Crist Rigott]

Originally Posted by old_coot88

I would try a couple of things first. Run a jumper from the 12BY7 cathode (pin 1) to pins 3 & 9. See if contrast improves.

If it does*, check resistance from the wiper to the top lug of the contrast control when it's rotated to max contrast. It should be zero or near zero ohms. If it is, try shorting out the 39 ohm resistor R109. See if that gives more grunt.

*Be sure jumper is removed.

When I jumper pin 1 to 3 & 9 contrast improves. Not a whole lot but an improvement.

When I short out R109 (with the jumper removed from pin 1 to 3 & 9), the contrast improves just barely.

Because the contrast pot is 5K, it doesn't take a lot of rotation to really change the contrast. BTW, with the contrast all the way up, I read 94 ohms from wiper to the pot end.

[Crist Rigott]

Originally Posted by Crist Rigott

When I jumper pin 1 to 3 & 9 contrast improves. Not a whole lot but an improvement.

When I short out R109 (with the jumper removed from pin 1 to 3 & 9), the contrast improves just barely.

Because the contrast pot is 5K, it doesn't take a lot of rotation to really change the contrast. BTW, with the contrast all the way up, I read 94 ohms from wiper to the pot end.

I jumpered a 3.3K resistor across the pot. This should give me 2K resistance and the rotation of the contrast pot is much better. I know it isn't linear, but very usable.

[dieseljeep]

Originally Posted by Crist Rigott

I jumpered a 3.3K resistor across the pot. This should give me 2K resistance and the rotation of the contrast pot is much better. I know it isn't linear, but very usable.

I think, I would've done the same.

[Crist Rigott]

I think my big problem is that the pot doesn't go to "zero" ohms. I don't think there is anyway around that except changing the control. I'll have to pull it from the chassis to see if there is a part number/mfgr that might help.