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Atari 130xe video issue


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#1 andrew@meler.us OFFLINE  

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Posted Fri Nov 10, 2017 9:51 AM

I purchased Atari 130xe - it powers up but has a video issue - basic screen flickers, self test runs but screen has lots of odd characters.

Any idea which chip to start with?

Sound works fine.  Power supply is NOT an issue, as I have 2 - both of them work on my 800xl, not on this 130xe

Couple of pics attached.

 

 

Thanks

Attached Thumbnails

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  • DSC_0019.JPG


#2 Paul Westphal OFFLINE  

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Posted Fri Nov 10, 2017 10:38 AM

Hmmm, looks like the GTIA but could also be ANTIC.



#3 Paul Westphal OFFLINE  

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Posted Fri Nov 10, 2017 10:38 AM

I wonder what a S.A.L.T. cart would say


Edited by Paul Westphal, Fri Nov 10, 2017 10:39 AM.


#4 andrew@meler.us OFFLINE  

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Posted Fri Nov 10, 2017 10:59 AM

I wonder what a S.A.L.T. cart would say

 

Thanks, I don't have S.A.L.T cart.  GTIA on this machine is socketed - so it should be easy to replace.  I searched eBay, don't see it there, will look for one at Best electronics.



#5 Paul Westphal OFFLINE  

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Posted Fri Nov 10, 2017 11:08 AM

He has a minimum order of $20. I suggest getting a new joystick PCB ($7.95) added to the order. GTIA's are $15, I believe.

#6 Paul Westphal OFFLINE  

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Posted Fri Nov 10, 2017 11:10 AM

FYI - ANY sockets on a 65xe or 130xe are very rare! You are lucky

#7 andrew@meler.us OFFLINE  

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Posted Fri Nov 10, 2017 11:16 AM

FYI - ANY sockets on a 65xe or 130xe are very rare! You are lucky

 

This machine would be pristine - if it worked.  But GTIA is definitely socketed.  Thanks for your help.

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#8 Nezgar OFFLINE  

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Posted Fri Nov 10, 2017 11:58 AM

Couldn't that also be bad RAM in the area of the display?

Probably a good use case for sys-check II

Edited by Nezgar, Fri Nov 10, 2017 12:09 PM.


#9 DrVenkman OFFLINE  

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Posted Fri Nov 10, 2017 12:09 PM

Couldn't that also be bad RAM in the area of the display?


Could be but probably not. I’ve had three bad GTIA chips in my personal collection - two XL computers and a 5200. All three had similar symptoms but RAM was fine.

#10 Level42 OFFLINE  

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Posted Fri Nov 10, 2017 2:15 PM

FYI - ANY sockets on a 65xe or 130xe are very rare! You are lucky

Not so rare, there were lots of bad GTIA,s in that era, although this looks like an early 130XE and the bad GTIA's only surfaced with the 65XE/800XE.

What IS really rare is the socketed MMU that no-one seems to notice.....I would first of all re-seat that......and the GTIA after it....


My money is on the two full banks of mT RAMs though.... if you're lucky it's only 1 or 2 or 3....

You can try piggy banking a good RAM on each mT one by one and power up....

Edited by Level42, Fri Nov 10, 2017 2:21 PM.


#11 Level42 OFFLINE  

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Posted Fri Nov 10, 2017 2:24 PM

Could be but probably not. I’ve had three bad GTIA chips in my personal collection - two XL computers and a 5200. All three had similar symptoms but RAM was fine.


But XL,s almost never had mT RAM,

Not sure about 5200s but I don't think they had mT either...

#12 _The Doctor__ OFFLINE  

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Posted Fri Nov 10, 2017 3:36 PM

also cut the two caps near the sio connector c 304 c 303, you sio devices will love you for it.

 

there appears to be a modification above the Atari pcb inlay next to the keyboard post and silk screen...  I don't have that on mine.

 

so do the re-seating touch up bad joints with leaded solder, and start the ram checking....no doubt it'll come back to life...


Edited by _The Doctor__, Fri Nov 10, 2017 3:43 PM.


#13 andrew@meler.us OFFLINE  

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Posted Fri Nov 10, 2017 8:08 PM

also cut the two caps near the sio connector c 304 c 303, you sio devices will love you for it.

 

there appears to be a modification above the Atari pcb inlay next to the keyboard post and silk screen...  I don't have that on mine.

 

so do the re-seating touch up bad joints with leaded solder, and start the ram checking....no doubt it'll come back to life...

 

 

Thanks for all the replies.  I ordered a GTIA chip from eBay, hopefully this will be the culprit.

If it was RAM - wouldn't the computer go to self-test (RAM test)?

I can actually get to the READY prompt / Basic - and start typing - video is distorted (as shown in my first picture).

 

I did reseat the MMU and GTIA - no change in behavior.



#14 _The Doctor__ OFFLINE  

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Posted Sat Nov 11, 2017 2:56 PM

if you get to the ready prompt type BYE or B. and press the return key

do you get the test menus? try each one at a time



#15 1050 OFFLINE  

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Posted Sat Nov 11, 2017 5:50 PM

Screenshot #2 shows self test in music mode so BTDT.

I've seen such garbage characters corrected by dropping
in a HCT08 for the standard 74LS08 at U18. This tells
me that it's something to do with timing and/or not so
square edges on system clock signals. Ram is of course
also involved but the root issue is the system timing
is tad bit off by perhaps a weak LS08 chip. One could
piggyback one onto U18 if it weren't for the useless
factory mod involving the pink and purple wires getting
in the way there. Just as a temporary test of course,
good results would dictate a proper entire replacement
then.

You could even remove the factory patch pink and purple
wires by restoring a cut trace on the bottom side of the
board and tossing these famous wires in the bin. It won't
make a hill of beans difference either way. It's GTIA's
chip select signal from the MMU IIRC.

I've never had to put one back whenever I've taken the time
to remove that factory patch. Highly suspect that management
made this fix up just to keep the repair team busy with
work stacked to the ceiling instead of letting them sit
around reading novels and having food fights.

#16 _The Doctor__ OFFLINE  

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Posted Sat Nov 11, 2017 6:53 PM

I wanted to see the different self test screens not just the one...

changing the 74ls08... why not do it while your waiting for your chip to arrive it will eliminate one more possibility...


Edited by _The Doctor__, Sat Nov 11, 2017 7:05 PM.


#17 andrew@meler.us OFFLINE  

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Posted Fri Nov 17, 2017 1:07 PM

Screenshot #2 shows self test in music mode so BTDT.

I've seen such garbage characters corrected by dropping
in a HCT08 for the standard 74LS08 at U18. This tells
me that it's something to do with timing and/or not so
square edges on system clock signals. Ram is of course
also involved but the root issue is the system timing
is tad bit off by perhaps a weak LS08 chip. One could
piggyback one onto U18 if it weren't for the useless
factory mod involving the pink and purple wires getting
in the way there. Just as a temporary test of course,
good results would dictate a proper entire replacement
then.

You could even remove the factory patch pink and purple
wires by restoring a cut trace on the bottom side of the
board and tossing these famous wires in the bin. It won't
make a hill of beans difference either way. It's GTIA's
chip select signal from the MMU IIRC.

I've never had to put one back whenever I've taken the time
to remove that factory patch. Highly suspect that management
made this fix up just to keep the repair team busy with
work stacked to the ceiling instead of letting them sit
around reading novels and having food fights.

 

The GTIA chips is not the issue - got a replacement one and the 130xe has the same behavior.

I'll look over the other suggestions this weekend.  I might just put it on ebay - too bad as the case and keyboard is pristine...






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