Jump to content
Sign in to follow this  
Colleton

Noob 800XL Questions...

Recommended Posts

Picked up a nice 800XL today.  Overall pretty pleased with it, but naturally there are a few flies in the ointment...

 

1.  Video looks a bit fuzzy even when using composite video (I'm using a monitor cable), and I can see "waves" running through the blue background when I boot into basic.  Replace capacitors? Every online resto video seems to recommend this.  FWIW, I have both a UAV and a Sophia on order.  Either of these should fix the video fuzziness, right?  Also, using S-Video just gives me a b/w image so I'm guessing one of the necessary signals is missing at the monitor jack?

 

2.  Some of the keys just absolutely do not work.  I've re-seated the ribbon cable, cleaned the end of the cable and the connector with contact cleaner.  No joy.  I took the keyboard apart and cleaned the mylar with alcohol, no help.

 

Failing keys:  Shift, Ctrl, J, K, L, ;, *, Z, X, C, V, B

 

I've been getting the same key fails since the first time I powered up the machine.  The traces on the end of the cable look pretty brown and nasty from the edge and back a few inches.

 

I knew that the keyboard was possibly going to be problematic from searches I've made here, but I am at a loss at this point.  Any help and advice would be greatly appreciated.  Thanks.

Share this post


Link to post
Share on other sites

for reasons unknown, atari did not connect the chroma signal to the monitor port. this results in s-video being monochrome.

the fix is as follows:

It would all depend on your MoBo revision. In general terms, all you need to do is:

1.    REMOVE C56 capacitor (if present). This will dramatically improve sharpness and "edge"-definition.

2.    Lift C54 right-hand side, preferably by inserting an on-off switch (if you want to preserve composite out). This will almost COMPLETELY remove vertical banding (present on Luminance-Y signal).

3.    Solder Chroma-signal wire from R67/R68 junction, to chroma pin in video port. This will enable the missing chroma-signal on the 800XL (the majority DO NOT have it enabled). No need for pick-up resistor (of any kind).


THAT'S IT.

 

for the keyboard, you may have to bend the contacts outwards in the motherboard connector. for reference, here is a diagram of which pins correspond to which keys:

800xl_07.thumb.gif.9bef7c8c6b327456555540bca8cc3293.gif

  • Like 1

Share this post


Link to post
Share on other sites
Posted (edited)

Nice, thank you!

 

If I'm reading the chart right I need to look at pins 5 (J K L ; + * Ctrl) and 8 (Z X C V B Shft)?  That corresponds exactly to what I'm seeing.

 

I have no idea how I could bend those contacts.

Edited by Colleton

Share this post


Link to post
Share on other sites
Posted (edited)

Without me thinking about this too much, if your machine is socketed then try reseating or swapping the two 4051 analogue keyboard multiplexers ( C4051BE ) and see if the problem moves to other keys. That's usually the most common fault after the mylar and the keyboard followed by the POKEY ( much less likely ).

 

 

 

 

Edited by shoestring
  • Like 1

Share this post


Link to post
Share on other sites

So, I just tried it.  Swapped the two chips and used a little contact cleaner on the sockets. 

 

Now I'm only failing keys L ;  Ctrl  and C V Shft.  Before it was J K L ; + * Ctrl and Z X C V B Shft.   So it did help.

 

I'll try again tomorrow.  Maybe a bit more contact cleaner and try re-seating the ribbon cable again.

Share this post


Link to post
Share on other sites
3 hours ago, xrbrevin said:

for reasons unknown, atari did not connect the chroma signal to the monitor port. this results in s-video being monochrome.

 

To save money on some parts. That can be the only logical conclusion.

 

Just look at the insanity in deciding the fate of the monitor port in the NTSC 600xls. Whilst other competitors still kept

it intact on their cheaper line of machines. 

  • Like 1

Share this post


Link to post
Share on other sites
6 hours ago, shoestring said:

It could be the socket. But I'm betting on one of the two chips being faulty.

 

In any case, replace both ( I would ). They're so cheap and common,  like 0.50c each.

 

https://www.digikey.com/product-detail/en/texas-instruments/CD4051BE/296-2057-5-ND/67305

 

Thanks, just ordered a couple.  Hopefully that will be the fix.  I appreciate the help.

Share this post


Link to post
Share on other sites

im the meantime, try operating the bad keyboard keys whilst 'wiggling' the ribbon cable in various places.

it may isolate the area of concern or at least confirm your ribbon & connectors are ok

Share this post


Link to post
Share on other sites

Thanks, xbrevin.  I tried it, no real change though.

 

It's either the chips or the ribbon cable.  I have the chips on order and have ordered a conductive silver paint pen from amazon.  I'll try the chips 1st.

 

Thanks everyone.

Share this post


Link to post
Share on other sites
On 8/12/2019 at 11:33 PM, shoestring said:

It could be the socket. But I'm betting on one of the two chips being faulty.

 

In any case, replace both ( I would ). They're so cheap and common,  like 0.50c each.

 

https://www.digikey.com/product-detail/en/texas-instruments/CD4051BE/296-2057-5-ND/67305

 

A big thanks to shoestring, as the replacement chips from Digikey arrived today and fixed the problem.  Thank you so much for the help!

  • Like 3

Share this post


Link to post
Share on other sites
On 8/13/2019 at 8:06 PM, manterola said:

There is also a new mylar design and production for 800xl/600xl coming up... 

 

Well, as a backup, I'd ordered a keyboard with new mylar from Best while I was waiting on the keys.  Ended up not needing it, but it's nice to have a spare.

Share this post


Link to post
Share on other sites
47 minutes ago, Colleton said:

 

Well, as a backup, I'd ordered a keyboard with new mylar from Best while I was waiting on the keys.  Ended up not needing it, but it's nice to have a spare.

You should have ordered the keyboard edge connector also, since sometimes that is the source of the problem. 

  • Like 1

Share this post


Link to post
Share on other sites

I meant to ask him what that was.  Is that the connector on the motherboard?

 

I'm sure I'll be ordering more from him, will add it to the list. Thanks!

Share this post


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

I meant to ask him what that was.  Is that the connector on the motherboard?

 

I'm sure I'll be ordering more from him, will add it to the list. Thanks!


As xrbrevin mentioned sometimes the contacts in the motherboard connector don't apply enough "pressure" tot he mylar. So that is why he recommended you to push those suspected contacts (the ones related with the faulty keys.... use the schematics)   against the mylar and see if that makes the keys work. Once I used a credit card between the mylar and the motherboard connector to push the mylar against the contacts (thats another trick to check if that is the problem).

Sometimes that specific problem can be solved by carefully moving those contacts a little to make them "touch" the mylar better. But sometimes that does not work or it is not possible or still you get a keyboard that works some times (not reliably) , so in those cases it is better to replace the motherboard keyboard connector using a new one with clean and strong new contacts.

 

  • Like 1

Share this post


Link to post
Share on other sites
On 8/15/2019 at 6:13 PM, Colleton said:

 

Well, as a backup, I'd ordered a keyboard with new mylar from Best while I was waiting on the keys.  Ended up not needing it, but it's nice to have a spare.

Now the new 600XL/800XL mylar membranes are out!

 

Share this post


Link to post
Share on other sites

Regarding the "waves" running through the video, can you show me a picture of the power supply you are using? I've found that when you get those waves a dead power supply isn't far behind, and that can take out the rest of the machine when it blows. 

  • Like 2

Share this post


Link to post
Share on other sites

chips

 

Funny, I just had the same problem, grabbed 10 of these mux chips for like 7 bux shipped I think, they worked great. Didn't want to wait for ebay ones from Asia that may more may not be good quality for 1$.

 

CD4051BE Single 8-Channel Analog Multiplexer, PDIP-16 from Harris,

 

chips

Edited by 7bits

Share this post


Link to post
Share on other sites
3 hours ago, orpheuswaking said:

Regarding the "waves" running through the video, can you show me a picture of the power supply you are using? I've found that when you get those waves a dead power supply isn't far behind, and that can take out the rest of the machine when it blows. 

Yeah, definitely check if you don't have the dreaded ingot power supply!

Power Supplies.png

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...
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...