Jump to content
Justin Payne

Video garbage on just obtained 1200xl

Recommended Posts

The RESET circuit does not come up clean sometimes due to a bad electrolytic capacitor, C7. 47ufd @ 10v. 

 

Bob

 

  • Like 1

Share this post


Link to post
Share on other sites
12 hours ago, Sugarland said:

Yes.. Also interested to learn more about the "asymmetrical clock" issue+fix. Searched forums and web with no results.

I pulled one  of the threads about it - under 1200XL Fix. How do I point to an old thread?

 

Bob

 

Share this post


Link to post
Share on other sites
25 minutes ago, bob1200xl said:

How do I point to an old thread?

Just go to the thread, copy the link location, and paste it here. Currently the forum software even creates some sort of sub-window, showing partially the first post, and means to go to that thread, either in the current tab or a new one.

Share this post


Link to post
Share on other sites
1 hour ago, bob1200xl said:

I pulled one  of the threads about it - under 1200XL Fix. How do I point to an old thread?

 

Bob

 

I think this is the thread?

 

 

  • Thanks 1

Share this post


Link to post
Share on other sites
45 minutes ago, ivop said:

Just go to the thread, copy the link location, and paste it here. Currently the forum software even creates some sort of sub-window, showing partially the first post, and means to go to that thread, either in the current tab or a new one.

Where is the link location?

 

Bob

Share this post


Link to post
Share on other sites
5 minutes ago, bob1200xl said:

Where is the link location?

Don't know which browser you use, but you probably have a location bar/field. That's the link. If you select the whole string, CTRL-C, and CTRL-V where you want to paste it. For example, this is a link to this current thread https://atariage.com/forums/topic/316719-video-garbage-on-just-obtained-1200xl/page/1 . I clicked display as link. If I don't do that, it becomes this:

 

 

Edited by ivop

Share this post


Link to post
Share on other sites
17 minutes ago, bob1200xl said:

Where is the link location?

 

Bob

Every post has a direct link option. Click that little widget and the link pops up for you to copy. Alternately, you can simply copy the address bar of your browser and then paste it into the post. 

 

 

A03E1676-16F3-4420-99BF-986E2BD44ECB.jpeg

24194AF4-21DF-465E-95F1-54E36152E437.jpeg

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, bob1200xl said:

Where is the link location?

At the top right of the post header there is a #??, right clicking will bring up a menu, "copy link location" copies the url of that post.

 

Edit: I see that @DrVenkman responded almost an hour ago.

Edited by BillC

Share this post


Link to post
Share on other sites
4 hours ago, bob1200xl said:

The RESET circuit does not come up clean sometimes due to a bad electrolytic capacitor, C7. 47ufd @ 10v.

Is this why I usually see a yellow screen during a power-on or reset of my 1200? It doesn't appear to have any ill effects.

Share this post


Link to post
Share on other sites
On 2/3/2021 at 9:32 AM, DrVenkman said:

The 1200XL has terrible stock composite video. It has a saturation boost in the circuit that is over-driving your TV’s ability to show a clean signal. If your video cable has separate chroma and luma connectors, try putting the Luma connector into your TV’s jack. You will have a B&W image, but you can see if the problems are limited to the composite signal at least. 

I doubt the saturation boost would do anything in the black areas of the screen like that. I believe all it does is crush the colorburst reference on the front porch during hsync, which shouldn't cause anything to appear in the black areas of the screen.

 

Any noise leaking into the composite signal from elsewhere in the Atari that raises the level up from black might cause it to look like that in the darker areas of the screen.

 

You can see that the noise covers the entire screen and seems to have patterning that changes in different areas of the screen. I'm not clear on which areas of the screen are not addressable by the display on an Atari (borders of the screen?) but if the noise is visible in such areas, it wouldn't be a logic problem (like video ram.) The patterning suggests that digital noise from other operations is leaking into the video signal, either from failing digital componnts (GTIA, transistors, diodes) filtering components (capacitors) or poor grounding somewhere.

Edited by rmzalbar
  • Thanks 1

Share this post


Link to post
Share on other sites
32 minutes ago, rmzalbar said:

Is this why I usually see a yellow screen during a power-on or reset of my 1200? It doesn't appear to have any ill effects.

I don't think so... the RESET failure happens when you get a spurious RESET while you are in the RESET routines. It hangs your system.

 

You see a yellow screen when the ANTIC/GTIA are reset - kind of a residual thing. You should see a black screen once the registers are loaded. Then the OS loads the Blue screen parameters.

 

 

Bob

 

Share this post


Link to post
Share on other sites
11 hours ago, bob1200xl said:

The RESET circuit does not come up clean sometimes due to a bad electrolytic capacitor, C7. 47ufd @ 10v. 

 

Bob

 

When you say, "bad", I'm assuming you mean that over time they dry out and just need to be replaced?

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...