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Black Screen issue with Colecovision

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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.

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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

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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

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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

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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

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Hello, I get a blank black screen whenever I attach the Coleco Vision (Atari) Module #1 to my Coleco Vision console. If I detach the Atari Module the console works fine, but attached it is just a black screen. I've cleaned both with alcohol and opened the module up and everything looks great! I don't understand why I get this black screen?! PLEASE HELP!??

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On 6/2/2020 at 8:38 AM, BigRen said:

Hello, I get a blank black screen whenever I attach the Coleco Vision (Atari) Module #1 to my Coleco Vision console. If I detach the Atari Module the console works fine, but attached it is just a black screen. I've cleaned both with alcohol and opened the module up and everything looks great! I don't understand why I get this black screen?! PLEASE HELP!??

Dumb question incoming!!!  Are you making sure there's not a coleco cartridge in the coleco when you're trying to use the atari module?

 

The atari module won't work or display an image if there's a coleco game in the coleco at the same time.  I'm sure that's not the case but I like to start simple first. :)

Edited by Ruggers Customs

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Big Ben, on the Atari expansion module if you get a blank screen when plugged in there are a couple of things to check. First clean both the expansion port connector on the Colecovision with some alcohol and do the same for the expansion module connector. If you are comfortable taking things apart, remove the expansion module cover. Then remove the little zif connector ribbon from its slot, clean it as well and reinsert it.

 

** Please do all of this with the power cable unplugged.

 

Hope that helps. ChildofCV was very helpful to me when I tried to fix my black screen issue with my Colelcovision. I never got it working, but he was a big help!!

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Did you ever get this #1 module working some days ?

There is at least 3 model : PAL, NTSC and Y/C used for French consoles.

The Y/C one is pin incompatible with the standard pal/ntsc consoles.

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On 6/12/2020 at 4:08 AM, emmanuelf said:

Did you ever get this #1 module working some days ?

There is at least 3 model : PAL, NTSC and Y/C used for French consoles.

The Y/C one is pin incompatible with the standard pal/ntsc consoles.

There's also the SCART-compatible version.  It has component (YPbPr) inputs that get passed directly through to the SCART.  The audio and external video switching signals moved to other pins which were unused on the NTSC and PAL versions.

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On 2/6/2019 at 10:38 PM, ChildOfCv said:

As a start, look at U22 pins 2, 4, 6, 8 and 10. They should be blinking.

 

My "black screen of death" Colecovision does NOT have a pulse on pin 10 of U22.  It is LOW.  But this is true of my working Colecovisions as well.  Did I miss something?

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I just haven't had the time to work on this at all. ChildofCV was a great help to me but I was unable to isolate the problem. My soldering skills are decent, but I wasn't sure if I was replacing bad modules and then maybe not soldering or removing chips without causing more issues. It might be a while before I get back to it. Thanks for checking.

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Posted (edited)
9 hours ago, KylJoy said:

 

My "black screen of death" Colecovision does NOT have a pulse on pin 10 of U22.  It is LOW.  But this is true of my working Colecovisions as well.  Did I miss something?

Most of U22 is used in the clock circuit, so yeah it's very important for that pin to be oscillating.

 

The oscillation will be slightly analog, but ought to be detectable by a logic probe.  Are you set on CMOS or TTL mode?  Should be TTL.

However, if pins 2 and 4 are pulsing, that could mean that the clock is working well enough.

Edited by ChildOfCv

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I have the probe set on TTL.  Pins 2 and 4 looked good so I'll assume we are fine there.  I will continue through the other steps listed in this thread to see where I get.  FYI, I tested every single IC from the problematic Colecovision in a second, fully socketed, motherboard and every one of them worked flawlessly.  I am able to use the Atari module with no issues

 

Thanks!

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31 minutes ago, KylJoy said:

I have the probe set on TTL.  Pins 2 and 4 looked good so I'll assume we are fine there.  I will continue through the other steps listed in this thread to see where I get.  FYI, I tested every single IC from the problematic Colecovision in a second, fully socketed, motherboard and every one of them worked flawlessly.  I am able to use the Atari module with no issues

Do you get sound output?  You can probe pin 7 of the sound chip for indications of life.

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I get either silence or a tone or multiple tones when powered on.  The screen goes completely black.  So some sort of video and audio are getting out of it.  I do also have an oscilloscope if you want to see any signals out of it.

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1 hour ago, KylJoy said:

I get either silence or a tone or multiple tones when powered on.  The screen goes completely black.  So some sort of video and audio are getting out of it.  I do also have an oscilloscope if you want to see any signals out of it.

When the sound chip is powered up, it's typically in a random state, and the first thing the BIOS does is silence it.  So the problem is in code execution.  Check the data and address lines for signs of life.  Check the BIOS chip pin 22 for signs of life after turning the system on.

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Pin 22 of the BIOS shoes a on boot but then goes low.

 

Edit: That is inconsistent.  Just now it was oscillating.

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17 minutes ago, KylJoy said:

Pin 22 of the BIOS shoes a on boot but then goes low.

 

Edit: That is inconsistent.  Just now it was oscillating.

Weird.  Pin 22 is active low, so having it hold low is not normal.

I forgot to mention, on various revisions, the socket for BIOS allows for the 28-pin EPROM in place of the 24-pin mask ROM.  Does your socket have 2 extra pins on each row?  Because I always started my numbering on pin 1.  If you have the mask ROM on such a board, pins 1, 2, 27, and 28 are not connected.

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Ah.  I saw that earlier in the thread.  I was on 22 of the 24 pin BIOS.  Pin 20 of the BIOS (pin 22 of the 28 pin socket) goes high and stays high on boot.

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3 hours ago, KylJoy said:

Ah.  I saw that earlier in the thread.  I was on 22 of the 24 pin BIOS.  Pin 20 of the BIOS (pin 22 of the 28 pin socket) goes high and stays high on boot.

It should be affected by U5, so that's your next target.  Pins 1-5 should pulse, and pin 6 should be high.  You can check 7, 9-15 to see if any of them pulse at all.  15 is what activates the BIOS chip.

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