vgcollector

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.

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!!

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

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

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.

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

ChildOfCv, I finally got back to my little project of fixing the black screen issue. I have ordered some new VRAM chips, but while I waited I went ahead and desoldered 2 good working ones from a Colecovision board I got that someone had butchered and it powered up correctly, but the controller ports an traces were shot. So I removed the 2 VRAM chips from the board. Now based on your comments about D4 being held down above. Do you think I should just replace the U4 vram chip and then see what happens. Then if I need to I can replace U3 as well? I have read a lot of the fixes for the Black screen issues and even though a lot of the topics never post what the solution is, a lot of them seem to point to the Vram. I think it has to be something that is fairly common with all the Colecovision boards. Thanks, my soldering skills are slowly improving.

I was going to ask you what pin can I put a set of ear phones on to hear music if I have Frogger is inserted. I have seen on the forum you can do it, but they don't mention which pin.

ChildOfCv, I appreciate all the help you have been!! I have learned a lot and I will keep posting with progress. I think I may just change the ROM chip to start since I have 2 brand new ones I got from Console 5. I will check the readings on U2 and U5 again to make sure I got them correctly. After the first couple of chips I tested I pretty much tested every chip 2-3 times to make sure I got a good reading. Do you have any kind of document that says what the reading should be on most of the chip pins on a working Colecovision. I do have a working one, and I may just crack it open and take the readings off each chip for comparison. If you have any part#'s for Colecovision chips you have ordered from Digikey or Mouser please let me know. I can identify chips that are the same, but then they have all the extra letters and I get lost. Thanks, I will post as I have updates.

First, where is a good source of replacement chips? I have a ROM chip, controller chips, and the newer DRAM chips, but I haven't found a place that sells the others except for China on ebay. Also when you refer to D4 what are you referring to there. If you were doing this what would you replace 1st? I can solder, but I was hoping to narrow it down some. Does the fact that the Expansion module work eliminate any of the chips you listed above. I appreciate all the help you have been. I have learned a lot. Thanks, Vgcollector

I did this and it blinked each time I hit the reset button.

Ok, tested the real U5 16 pins.Just to clarify the first set of readings is for U2, and the 2nd set is U5.

The test above was for U2. Testing U5 now.

I tested CPU pin 22 and it was High, no blinking, and High tone. I tested the U5 chip and mine had 24 pins(short chip) so 1 and 2 were empty as well as pins 27 & 28. So just to clarify the first chip I did the reading on was #3. Let me know what you think of these readings. Thanks

Sorry I didn't see your reply to my post I will check these tonight. I usually get an email on new posts, and I didn't check. Thanks

Thanks for the reply!! The unit works fine, but it has a screen glitch on Donkey King on the 2nd & 3rd screens where one block isn't displayed correctly. Everything else is fine. Thanks, Vgcollector

Hi, I tried to copy the U3 & U4 second readings list from my spreadsheet but it wouldn't let me attach it or copy it in. I have attached a snip it of what my findings were. Let me know what you think.

Sorry for the late post on this, but here are my latest readings on U3 & U4. I put these into Excel so I could concentrate on the readings. Second Test Chip U3 Chip U4 Pin# Low/High Blinking Tone Pin# Low/High Blinking Tone 1 Both Yes Low 1 Both Yes Low 2 Both Yes Low 2 Both Yes Low 3 Low Yes Low 3 Low Yes Low 4 Both Yes High 4 Both Yes High 5 Both Yes Low 5 Both Yes Low 6 Both Yes High 6 Both Yes High 7 Both Yes High 7 Both Yes High 8 High No Low 8 High No Low 9 Low No High 9 Low No High 10 High No High 10 High No High 11 Both Yes High 11* Low Yes Low 12 Low Yes Low 12 Low Yes Low 13 Low Yes Low 13 Low Yes Low 14 Low Yes Low 14* Low No High 15 Both Yes Low 15 Both Yes High 16 Both Yes Low 16 Both Yes High 17 Low No High 17 Low No High 18 High No Low 18 High No Low I put an asterisk next to the readings on U4 that were way different than U3. Thanks. I was a little more precise this time.

One other question. If there is a broken trace, am I looking for the break on the top of the board or on the bottom. I figure I might as well check the traces while I am testing the pins.

I have not seen any evidence of prior work on this board. All of the solder joints seem to be original. I think I could spot that especially as close as I have looked at this particular board. I will check those spots tonight and update my post when I get that done. I will also look for broken traces. I would think that a broken trace wouldn't happen with the board seated like it is. Is there any chip you are leaning towards as being the culprit yet? Thanks

Thanks for the pictures. That helps to see how they are connected. I will redo these readings tonight.

I tested U3 and U4. I did want to let you know that on this one I got some different readings and tones. I will try to describe what I saw on the probe as well as I can. U3 1-low/high lights lit blinking low tone 2- low/high lights lit blinking low tone 3- low/high lights lit blinking low tone 4- low/hgih lights lit blinking high tone 5-low/high lights lit blinking low tone 6- low/high lights lit blinking high tone 7- low/high lights lit blinking high tone 8- low/high lights lit blinking high tone 9- Low 10-High 11-Low Blinking 12- Low Blinking 13- Low Blinking 14- Low Blinking 15- Low Blinking 16- Low Blinking 17- Low 18 - High U4 1- Low/High lights lit Low tone 2- Low/High lights lit Low tone 3 - Low light lit Blinking 4- low/high lights lit blinking high tone 5- low/high lights lit blinking high tone 6- low/high lights lit blinking high tone 7- low/high lights lit blinking high tone 8- High 9- Low 10-High 11- Low lit Blinking 12- Low lit Blinking 13- Low lit Blinking 14- Low lit Blinking 15- Low/ High lit Blinking 16- Low/High lit Blinking 17- Low 18- High I hope this is clear to you. I don't know if you have a spreadsheet with all these readings, but I was thinking about doing the readings on a working Colecovision and then comparing it to what we are finding with this broken one. I think a spreadsheet might be helpful in organizing all of this. Thanks

Ok, here is my latest testing results. I verified power voltages are correct. I plugged in Frogger, no sound. I plugged in Atari Expansion Module, got picture and sound. With Frogger plugged in cart slot U9 Results- Exception indicates does not match your expected results Pins 1-8 – Blink Pin 9- High- Exception Pins 10 & 11- didn’t test Pin 12 – Low Pin 13 – Blinking Ping 14 & 15 –High Pin 16 – High- Exception Pin 17-20, 22-24 – Blinking Pin 21 – Low- Exception Pins 25-32 – Didn’t Test Pin 33 – High Pin 34 – High Pins 35, 36, & 38 – Didn’t test Pin 37 – Blinking Pin 39 – Low- Exception Pin 40 – Blinking U6 Pin 1 – High Pins 2-3, 6- Blinking Pin 4 – High-Exception Pin 5 – Low Pin 6,7 – Didn’t test Pin 8 – Low Pin 9 – High – with Frogger plugged in- Exception Pin 10 – High Pin 11 – High- Exception Pin 12 – High- Exception Pin 13 –High- Exception Pin 14 – High Pin 15- High Pin 16 - High FYI, I saw in the CV technical manual that if you have a black screen after playing for a while, check the polarity of C106 which is a 10 uf tantalum. How do you check polarity. This may have nothing to do with the issue but just wanted to tell you I ran across it. It says to replace it if the polarity is wrong. As always I appreciate the Help!!

Hi, thanks for the additional conditions to check so we are both on the same page. I will test all of these conditions on the Colecovision I am working on. I will test these and then test the pins on VDC again. It will be later this afternoon as I am not home right now. Thanks

Ok, sorry, I misunderstood what you were saying about the pin numbering being the opposite on this chip. I will retest tonight and post my readings. FYI, I am doing all these tests with power on, a cartridge inserted, and 1 controller plugged in port 1. Is that how I should be testing?