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Black Screen issue with Colecovision


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#76 vgcollector OFFLINE  

vgcollector

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Posted Sun Mar 17, 2019 11:40 AM

I meant the SRAM, sorry for the confusion. I will try the U4 chip first, and then see what happens. Hopefully I can get this done in the next few days.I will update you when that's done hopefully with some good news. Thanks!!

Thanks

I replaced the U4 SRAM chip with no change. I am going to change out the U3 chip next.It will probably be later in the week before I have time to do this.



#77 ChildOfCv OFFLINE  

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Posted Sun Mar 17, 2019 4:55 PM

Well, U3 isn't on the bad data line, so I wouldn't be so quick to swap it out.  Turn your attention to U18 and U19 next.  At the least, pull the chips and see if a short to ground still exists on the dead data line as seen in post 67.


Edited by ChildOfCv, Sun Mar 17, 2019 4:57 PM.


#78 vgcollector OFFLINE  

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Posted Sun Mar 17, 2019 5:04 PM

Ok thanks, I will start looking at those. Does it matter which one I do first? I have a couple of sets of these.

Thanks

#79 ChildOfCv OFFLINE  

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Posted Sun Mar 17, 2019 5:48 PM

No, we're only looking for one that causes a short on that data line.  And we only have the process of elimination with current equipment.

 

I'd pull player 1's first I guess though.  Then see if you still see a short to ground.  Then try player 2 without putting player 1 back yet.

 

In fact, I'd leave out any chip I pull until the one that eliminates the short is found.  Then they can be restored one by one, still making sure the short isn't back.


Edited by ChildOfCv, Sun Mar 17, 2019 5:50 PM.


#80 vgcollector OFFLINE  

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Posted Today, 6:17 AM

I finally got back to this. I apologize for the big gaps right now, but my son plays college baseball so during the season I don't have as much free time. I replaced controller chip for player 1 with no change. I have it socketed so I can pull it easily. What is the best location to check with the logic probe to check for the short to ground. I will busy for a couple more weeks and then I should be able to get back at it a little more frequently. Thanks



#81 ChildOfCv OFFLINE  

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Posted Today, 11:00 AM

I finally got back to this. I apologize for the big gaps right now, but my son plays college baseball so during the season I don't have as much free time. I replaced controller chip for player 1 with no change. I have it socketed so I can pull it easily. What is the best location to check with the logic probe to check for the short to ground. I will busy for a couple more weeks and then I should be able to get back at it a little more frequently. Thanks


The logic probe can't tell you about shorts.  Not part of its mission statement.
 
To check for a short, turn off the power and use the multimeter in diode mode.  If you see a low voltage, you have a short.  You may also be able to get a reading in ohm mode.  You'd be checking any of the locations in the picture in post #67.


Edited by ChildOfCv, Today, 11:05 AM.





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