vertical lines on many XE computers

[flashjazzcat]

issues with my machines now. I never tried hooking them up to a modern TV. But I cannot get a decent picture. How are you getting such sharp moire-free images? Even when I have my camera set to 1/60sec exposure (NTSC TV) I get some moire pattern in the image. The camera is a Nikon Coolpix L100. I have not spent any time exploring all the settings yet. Hopefully I can coax a decent image out of it this weekend.

I'm using a Fuji F50 compact on auto, no flash, macro setting. The moire images are avoided in two ways: sometimes by taking the picture at an angle, and in all cases downsampling the resulting 12MP image in Photoshop to about 30% of its original size. Preserves detail but patternation tends to be eliminated.

[flashjazzcat]

Almost accidentally, I've just about cracked the XE s-video problem (at least when used with this LG TV of mine). The 130XE I killed yesterday and fixed this morning was my test-bed for the video mods and in my struggle to get it running again, I patched the colour circuit up with a diode. When it finally came back to life this morning, I was pleasantly surprised by the quality of the display:

 

 

 

This is a fairly simple mod involving stripping out the RF modulator, adding a diode and changing a couple of resistors to taste (like my "UltraVideo XL 1.0" mod, it can be used with as much or as little as you want of the Supervideo mod). I'll try and get it written up in the next few days.

[w1k]

Almost accidentally, I've just about cracked the XE s-video problem (at least when used with this LG TV of mine). The 130XE I killed yesterday and fixed this morning was my test-bed for the video mods and in my struggle to get it running again, I patched the colour circuit up with a diode. When it finally came back to life this morning, I was pleasantly surprised by the quality of the display:

 

 

 

This is a fairly simple mod involving stripping out the RF modulator, adding a diode and changing a couple of resistors to taste (like my "UltraVideo XL 1.0" mod, it can be used with as much or as little as you want of the Supervideo mod). I'll try and get it written up in the next few days.

 

can i use Super video for fix this lines?

 

http://www.retrocomputing.net/parts/atari/130xe/docs/sv130-1.html

[flashjazzcat]

can i use Super video for fix this lines?

 

http://www.retrocomp...cs/sv130-1.html

In my experience - with the equipment I use - SuperVideo made the lines worse, since it simply appeared to overdrive the video circuit. My mod involved removing the RF modulator and replacing R205 with a diode (size as yet unspecified - I pulled it off an old XM301 board and I can't see the numbers on it properly). Beyond that, any alterations you want to make to the circuit as per the SuperVideo mod are done at your own discretion.

 

I'll make PDF instructions in the next couple of days if you can hang on.

[rchennau]

For some really dumb reason (to which I'm not at liberty to discuss) I removed the 1.2K resistor in R54. Radio Shack doesn't carry 1.2K 1/4 resistors. Fortunately I still have the old one and can solder it back in. However before I do is there a better option for R54? What is its purpose in life? Is there an Atari 800XL reference manual that fully describes the circuit board?

[Rybags]

800xl.zip

 

Schematics in there.

[Kjmann]

For some really dumb reason (to which I'm not at liberty to discuss) I removed the 1.2K resistor in R54. Radio Shack doesn't carry 1.2K 1/4 resistors. Fortunately I still have the old one and can solder it back in. However before I do is there a better option for R54? What is its purpose in life? Is there an Atari 800XL reference manual that fully describes the circuit board?

R54 Does not need to be changed. You should put it back.

 

=)

[dmlloyd]

If it's of any interest to anyone - I recently completely replaced the video circuit in my 600XL with a S-Video circuit I designed myself. The Luma circuit is basically the same 600/800XL circuit but the chroma circuit is a duplicate of the XE circuit. And wouldn't you know it - vertical banding! BUT only when Chroma is connected (I wired up my s-video as separate RCAs for luma and chroma and in my circuit they're completely isolated from one another [aka no composite or RF out at all]).

 

So this may be a hint as to what's going on here. I wonder if it has to do with the shape of the chroma waveform (it's basically a square wave)? Maybe softening it up with some capacitance might help, we'll see.

 

Anyway it doesn't bother me all that much but I thought this info might be useful.

[+bob1200xl]

The objective of the LUMA is to deliver the amplitude of the video signal. The CHROMA delivers the phase of a 3.58mhz reference signal. The vertical lines are probably the result of CHROMA leaking into the LUMA circuits, either in the monitor or the Atari. A composite decoder filters out the 3.58mhz, S-Video does not, so you want as little CHROMA amplitude as necessary.

 

Bob

 

 

 

If it's of any interest to anyone - I recently completely replaced the video circuit in my 600XL with a S-Video circuit I designed myself. The Luma circuit is basically the same 600/800XL circuit but the chroma circuit is a duplicate of the XE circuit. And wouldn't you know it - vertical banding! BUT only when Chroma is connected (I wired up my s-video as separate RCAs for luma and chroma and in my circuit they're completely isolated from one another [aka no composite or RF out at all]).

 

So this may be a hint as to what's going on here. I wonder if it has to do with the shape of the chroma waveform (it's basically a square wave)? Maybe softening it up with some capacitance might help, we'll see.

 

Anyway it doesn't bother me all that much but I thought this info might be useful.

[+Stephen]

Bumping an old topic so I don't start a new one. I have posted 5 screenshots of two different 130XEs. One modded, one stock.

 

Vertical Banding

[Rybags]

I'm really starting to think the ultimate "standard" S-Video/Composite upgrade would be a board that just picks off the signals direct from GTIA and has it's entire own power supply and is isolated in a nice shielded box to keep all the noise out.

[+Stephen]

I'm really starting to think the ultimate "standard" S-Video/Composite upgrade would be a board that just picks off the signals direct from GTIA and has it's entire own power supply and is isolated in a nice shielded box to keep all the noise out.

I'm sure that would be a big help, but I don't think it will solve the issue of incorrect de-interlacing. I don't have a modern display that works properly with my A8's native signal, and I know my 1084S is not going to last forever. Besides that, it's very hard to go back to fishbowl CRTs!

[Rybags]

The issue with monitors or capture cards thinking you are sending an interlaced signal can't really be resolved.

 

The best solution would be on the computer software side. Just have every second frame set PF1 to the PF2 colour.

 

Problem is that it would be OK for some software, not good with most games, and not good with FlickerTerm.

[+bob1200xl]

Sure it can... the best solution is a transparent hardware hack.

 

Bob

 

 

 

The issue with monitors or capture cards thinking you are sending an interlaced signal can't really be resolved.

 

The best solution would be on the computer software side. Just have every second frame set PF1 to the PF2 colour.

 

Problem is that it would be OK for some software, not good with most games, and not good with FlickerTerm.

[Kjmann]

I've been doing a lot of work on this in the past month or so and have come to a couple of conclusions.

 

1 - Vertical Banding has a lot to do with how strong the chroma signal is.

 

it seems that the stronger the chroma signal the more vertical banding you get.

Although this doesn't seem to be a "Chroma Bleeding in to the Luma Circuit" Issue.

In Fact Severing the Contact between the Chroma and Luma Circuits (the connections

used for Composite Video) Doesn't seem to make any difference at all.

 

 

2 - CRT's have this Problem to a Much Smaller Degree versus LCD's.

 

The Banding is More Apparent on LCD monitors than on CRT's. In Fact, On most CRT

Monitors with S-Video Inputs the banding is Definitely lighter and sometimes Non-Existent.

[flashjazzcat]

I've been doing a lot of work on this in the past month or so and have come to a couple of conclusions.

 

1 - Vertical Banding has a lot to do with how strong the chroma signal is.

 

it seems that the stronger the chroma signal the more vertical banding you get.

Although this doesn't seem to be a "Chroma Bleeding in to the Luma Circuit" Issue.

In Fact Severing the Contact between the Chroma and Luma Circuits (the connections

used for Composite Video) Doesn't seem to make any difference at all.

I did a lot of experiments in this area a year or so back, with the disadvantage of having very limited understanding of electronics. However, in the case of the 800XL circuit, I absolutely found that isolating the chroma and luma circuits worked wonders when using an LCD panel. To this day it looks nearly as good as VBXE output. However, each machine is different and I've found you really can't make generalizations about what will work and what won't in a specific case. A few people did my UltraVideo XL mod (which was loaded with caveats and disclaimers), and had varying degrees of success. Most noticed an improvement.

 

It's a different story with CRTs. My 1084S still shows artifacting from the machines I sweated over for weeks, and which show no artifacting at all on an LCD panel. This is often because the monitor itself does not isolate the two signals, so the problems you worked hard to resolve crop up all over again.

 

2 - CRT's have this Problem to a Much Smaller Degree versus LCD's.

 

The Banding is More Apparent on LCD monitors than on CRT's. In Fact, On most CRT

Monitors with S-Video Inputs the banding is Definitely lighter and sometimes Non-Existent.

This is absolutely true.

 

If there was a cheap adapter which made the Atari produce an RGB signal at source I'd stick one in every machine I own. I don't really like using CRTs with stock Ataris, but the VBXE machines look glorious through an SC1435 or 1084S. No tuning or tweaking required, and they knock spots off LCDs for clarity.

[mimo]

I have also noticed that the effect is more pronounced on better quality LCD TV's. I have a cheap non branded 19" LCD that does a brilliant job with s-video, no banding visible at all. My LG 19" LCD show banding and my 26" Sharp Aquos looks awful

[Kjmann]

 

I did a lot of experiments in this area a year or so back, with the disadvantage of having very limited understanding of electronics. However, in the case of the 800XL circuit, I absolutely found that isolating the chroma and luma circuits worked wonders when using an LCD panel. To this day it looks nearly as good as VBXE output. However, each machine is different and I've found you really can't make generalizations about what will work and what won't in a specific case. A few people did my UltraVideo XL mod (which was loaded with caveats and disclaimers), and had varying degrees of success. Most noticed an improvement.

 

It's a different story with CRTs. My 1084S still shows artifacting from the machines I sweated over for weeks, and which show no artifacting at all on an LCD panel. This is often because the monitor itself does not isolate the two signals, so the problems you worked hard to resolve crop up all over again.

 

Yeah john, your work is the reason that I decided to pursue this further. =)

 

I Do an S-Video Upgrade in Every System that I get in Stock for the Store and More Times than not, Cutting the Connections doesn't seem to make a difference.

I've done nine 800XL's and four 600XL's in the last 6 months. Only on three of the 800XL's did it make a difference. I'll Go Back and Check My notes, maybe this has a Common Element. Perhaps the 3 boards that it made a difference on were the same motherboard revision?

 

To Solve this Problem I added a Switch assembly to my S-Video Upgrade Board. the Switch Gives two Different Strengths of the chroma Signal. one is a about 95% and the other is about 65%. When The Switch is Set to %65 Chroma Signal Strength, LCD's Look Way Better and the Vertical Banding All But Disappears. Even the color is nice and Rich.

 

But, When a System is on a CRT, The Colors Tend to look a little Washed out. Switching to The 95% Strength Signal seems to make a huge difference.

 

Also When Using an S-Video to Composite Adapter, the Different chroma Signal also need adjusting. you need the 95% Setting for this otherwise you get Green and Red Shadows on your Graphics.

 

Although, due to the many differences in motherboards over the years and the different results that people get like you were talking about john, I still include in the instructions for clipping of the 2 components that connect the signals in the circuit. =)

[w1k]

any photos about this mod?

[sloopy]

any photos about this mod?

 

here are the install instructions (this is a zip file to download)

 

 

sloopy.

[w1k]

jou thanks

[Bryan]

A possible theory on what's happening with the banding:

 

The color carrier is supposed to be a shifting sine wave at the proper frequency for NTSC or PAL, but GTIA puts out a square wave which is run through some combination of filtering components to round it off a bit. Perhaps there's still too many out of band harmonics which leak through the monitor's chroma filters and appear on the screen. Otherwise, unless you're dealing with really strong saturated color (which the A8 isn't able to produce since the carrier is always at the burst reference level) the color carrier should be just about impossible to see.

[GoodByteXL]

Besides experimenting with the hardware available another solution for XE is:

 

- desolder the hf box

- add instead the video circuit used in the XL

- add a super video (or svideo mod)

[w1k]

i have ultra video 2xe and vertical lines still visible.

[Rybags]

My XEs can get the same thing depending on what video source I choose.

 

The banding tends to be coincidental with the pixel clock / 1.77 MHz clock (PAL), so maybe too much blame is being devoted to the colour circuitry. Also, like many Ataris, you can get a tendency for the interference to be stronger when a Refresh cycle starts.