loottool

To be honest I have only tested the memory with the probe. A friend at work let me borrow it. I really don't know what I am doing when it comes to the circuit board level of electronics. I am trying to learn. I found a post on digital press about the memory posted below. Everything is the same but number 3 I get low/pulse on all the chips at point 3. I really don't think that is the problem. The trouble shooting guide from coleco posted on coleco vision zone leads me to start with chip U9:36 to see if that point is good but I don't know what to look for. I believe this is the video chip. I am testing it using the probe connected to negative and +5 off the power supply. I have also checked the voltage all the way to the switch. The voltage it right. past the switch. anything you can do to help is appreciated Daniel From Digital press "Bad memory/RAM chips can result in problems like distorted graphics or text. Figuring out which chip(s) needs to be replaced can be done easily with a logic probe. Set the probe to pulse and TTL/LS. Looking at the motherboard (with the cart port towards you), the memory chips are in the upper-right area and are labeled U10-U17. With the system on, probe the pins on each chip. Here's what you should be seeing: 1) LOW 2) PULSE 3) HIGH 4) PULSE 5) PULSE 6) PULSE 7) PULSE HIGH 9) HIGH 10) PULSE 11) PULSE 12) PULSE 13) PULSE 14) PULSE 15) PULSE 16) LOW If a pin gives you a different reading than what's listed, the chip is bad and needs to be replaced."

well I borrowed a logic probe and I also have a diode tester / multi-meter that I am going to try and trouble shoot my system with. If anyone has some pointers or words of wisdom please share them. Thanks

thanks for the response. I thought that the expansion mod was still using the rf of the colecovision to output the signal but I could be wrong. anyone know for sure? Daniel

I feel confident that it is not the switch as I get 12 and 5 volts to and from the switch. Is there a way to check the video chip? if it was the rf then exp mod 1 shouldn't work. right? I am wanting to do the video mod but I am not certain that its going to fix my problem. Thanks for the suggestions. Anyone out there that can help trouble shoot the video chip??? Daniel

Was wondering if anyone could walk my through fixing my Colecovision? I have checked the power supply and I get the correct voltages at the board, the plug, and after the switch. I originally thought the problem was the cartridge slot so I replaced that only to find out that the console should show insert cart screen with nothing in the deck. I guess that was a wasted effort. It was working about 2 months ago and I have had it for about 5 years. The screen shows as a perfectly black screen turning it on and off sometimes creates a screwed up screen (not related to colecovision start screen) and a humming sound. I have checked the reset switch. It makes and breaks as a switch should. I hooked up the expansion mod 1 and plug pac-man in and it works perfectly. so I would guess that the rf modual is working as it should. My best guess is the video chip is bad but I am only guessing from the repair manual I have says check chip u9 video circuit. Anyone know how?? and old link with a similar problem but never solved link can anyone help me?? thanks I am new here Daniel