vgcollector

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.