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Ahhhrrr got VRAM problem I guess :(


CrazyBoss
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Hi

 

No pictures, but after 5-10mins sprites start to look weird, other graphics still look ok. Then I can reset, and sometimes I will se the Colecovision logo with other colours than normal, but the letters are the same shape.

 

The most weird is switch off and on will solve the problem for some time and then it return.

 

I did replace the powerswitch.

 

Maybe will show some pics later. But I do think its a VRAM problem.

 

I really dont have time for hardware problems, have some ColecoVision projects that have to be finished soon :(

 

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Yep, it could be a VRAM problem.

 

I bought recently a Colecovision and it has almost all VRAM bad, my fault because I only ordered 5 replacement VRAM, I need to order more.

 

Besides I discovered afterwards that the VDP was damaged, so I replaced it, so far all repairs have been adding up in price... :ponder:

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My power cord to the Colecovision is sensitive. Make sure it's snugged in nicely and the wires not crossing any other cord like RF cord, controller cord. My Colecovision sprites sometimes get misaligned if it goes over 128 x-position due to flakey power issue which makes Knightmare much harder to play.

Edited by Kiwi
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I got 15 of them. Only need 8. I hope I don't screw it up. So far 1 hour in and one chip removed without screwing up 7 more to go. Very hard to cut the pins. I have 3 different cutters and think maybe a dremel or something to cut the pins near the top of the chips. If it does not work I will buy juice's new board when its done that way I dont have to throw it all out.

These colecos and intellivisions are extremely delicate and failure prone compared to the atari 2600 and 7800 systems I am used to.

It is great someone is making a new board as these things would be extinct in the near future.

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I used a dremel with a small cut off wheel then desoldered all the pins then used a needle to clean out the holes then checked traces 1 was bad(all green) and soldered in 4 chips and fixed the trace with a jumper. only 4 more to go and will see if it works. Total time so far? 5 hours.

I have to keep telling myself not to use the coleco for skeet shooting if this does not work.

But one thing for sure is people that repair these for 20 bucks or whatever have servere levels of patience and can do the monotonous with ease as for me I would not replace the ram chips for no less than 200 bucks as it is crazy hard. Plus my wife wants me to work on the house etc. and says your playing video games all day long when I am not really having much fun at all. :(

Best of luck to you on your ram fix!

Do ya think I should get back at it after having a couple drinks? :P

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I used a dremel with a small cut off wheel then desoldered all the pins then used a needle to clean out the holes then checked traces 1 was bad(all green) and soldered in 4 chips and fixed the trace with a jumper. only 4 more to go and will see if it works. Total time so far? 5 hours.

I have to keep telling myself not to use the coleco for skeet shooting if this does not work.

But one thing for sure is people that repair these for 20 bucks or whatever have servere levels of patience and can do the monotonous with ease as for me I would not replace the ram chips for no less than 200 bucks as it is crazy hard. Plus my wife wants me to work on the house etc. and says your playing video games all day long when I am not really having much fun at all. :(

Best of luck to you on your ram fix!

Do ya think I should get back at it after having a couple drinks? :P

 

 

Amazing that only one was bad. So far in my soldering life of ~24 years, those VRAM chips are the worse. I like Matthew's idea of installing F18A and leaving the chips alone. F18A is VGA, but TPR and some other folks use VGA to HDMI adapter, so it connects to HDMI TV.

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Ok another trace was bad. Now I got it to start a game and can play but can not see the screen just static. Would never start a game before. Maybe power switch or rf problems?

Ok not the power switch, took apart the rf and all ok there too.

Does anyone have pics of the board with the ram chips out? I am questioning a trace but hard too tell with the chips in.

spent 12 hours on it today.

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the saga continues here, I did not do any work on the ColecoVision, but I think its not a VDP or VRAM problem, could be something else. Cause in the middle of a game suddenly the controller start to fail, could not move my player left and right, and then suddenly it worked again, but the keypad did not respond, I reset the console and got the "COLECOVISION" logo, with wrong colors. So I suspect it to be some electronics controlling the I/O ?

 

This time I did not see any problems with the sprites, but its not for sure the spritepattern was the same area of the two games.

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I saw one wiki where the guy cut the pins of the original ICs and just soldered the new memory chips to the old legs.

That could be done but what is the fun in that. I spent all day last saturday dremeling chips unsoldering each pin and cleaning out the holes with a needle and then fixing 2 traces and soldering in the chips just to hear DK sound and not even get a picutre. 128 connections later my eyes, back and brain was toast(from the flux)
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There is a problem with the needles, these can "damage" the pin (a kind of extruded small donut) that makes contact between upper and lower layer, so you'll need to solder both over and under.

 

I prefer to use a basic solder extractor with spring.

I soldered both sides too. I have no solder extractor.

I will check continuity better to make sure from the chip legs it is good thru the board.

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Pin 36 has the comvid terminal on the vdp chip. Can a person get composite video from there and get a good picture? If so why do a composite mod on the rf box? Doing more tests tomorrow.

 

You get B&W composite video only, it needs a mixer circuit to put the color.

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Ok thank you again!! Here is the results rcas connected to vdp and sound chips. Perfect picture and sound sans color. The controller even works except the fire buttons.

So with the top of the rf mod off the board as you can see where do I go from here? Any way to get color with a screwed up rf?

post-27194-0-40564500-1447259544_thumb.jpg

post-27194-0-13593500-1447259606_thumb.jpg

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Ok thank you again!! Here is the results rcas connected to vdp and sound chips. Perfect picture and sound sans color. The controller even works except the fire buttons.

So with the top of the rf mod off the board as you can see where do I go from here? Any way to get color with a screwed up rf?

 

Excellent! well, there is a trick with the RF module, usually when you desolder the connector, you break the lines in PCB, check for continuity between pads and lines, repair them and it should work again.

 

Don't forget to check it is in channel 3.

 

Don't forget to replace the CMOS chip.

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