Brianeric26 Posted December 17, 2016 Share Posted December 17, 2016 Hey my colecovision , when I first bought it it was having a bad rf problem , so I decide to av mod it , so I followed the ben heck tutorial , and yeah it worked really welll , so time has passed have pased and I decide to use my colecovision again with the expansion module #1 and it worked flawlessly , but when I tested the colecovision without the module (because I dont have games for it ) it showed the colecovision bios screen but all green and with lines , and when the bios disappear the lines still there , however with the expansion module it work flawless , so I thinking my self ok the atari is working because it is it on thing its has it video processor(tia) ,cpu ram etc , buttt it uses the video circuit of the coleco so that tells my that the video circuit is working , so my guess is that the vdp has gone bad or the ram , because I already refurbished the power switch and power supply is working awesome , (btw the picture is way worse with rf but still have the same issues ),(and I already re do the the av mod with new parts and still the same ) anyone that can help me with it ? I am confident with soldering , I replaced the expansion module cpu one time , so im ready for the repair , the only thing is I have to be sure what really is the IC that is making this problem ,thanks in advance for you help Quote Link to comment Share on other sites More sharing options...
cdn2a Posted December 21, 2016 Share Posted December 21, 2016 Some really good advice given to me was use the Coleco frogger game. Your right, the test with exp mod 1 proves RF circuit. Coleco frogger, since it plays music, right from the get go, will allow you to diagnose either CPU, reset, Sram, controls etc, OR Vram/VDP. If you get sound but no pic, then its Vram/VDP, no sound, and your on to CPU clock, etc. If you Vram is socketed, it might just need to be reseated. Good luck. Quote Link to comment Share on other sites More sharing options...
Brianeric26 Posted December 21, 2016 Author Share Posted December 21, 2016 Thanks the only work I have done is the av mod ,I dont have any colecovision game but , i will be in search for frogger in specific Quote Link to comment Share on other sites More sharing options...
+nanochess Posted December 21, 2016 Share Posted December 21, 2016 Test pin 36 to center of RCA jack, ground the side. You should get a crisp B&W picture on your TV, if it isn't then the VDP is bad. Quote Link to comment Share on other sites More sharing options...
Brianeric26 Posted December 22, 2016 Author Share Posted December 22, 2016 Test pin 36 to center of RCA jack, ground the side. You should get a crisp B&W picture on your TV, if it isn't then the VDP is bad.Wheres is pin 36 in the expansion bus orr where ? Thanks very much for you reply Quote Link to comment Share on other sites More sharing options...
+nanochess Posted December 22, 2016 Share Posted December 22, 2016 Wheres is pin 36 in the expansion bus orr where ? Thanks very much for you reply Pin 36 of VDP chip. Quote Link to comment Share on other sites More sharing options...
Brianeric26 Posted December 22, 2016 Author Share Posted December 22, 2016 Pin 36 of VDP chip. At firts it gave me a garbagr b/w image but I changr to another rca cable , and it gave me a clean b/w picture , so I left it there turn on , and try to replecate de bad b/w image and nop, it was a bad rca cable , so the vdp is not bad great , I have the pictures , i will upload them later , but still i haven find whats wrong with my colecovision Quote Link to comment Share on other sites More sharing options...
Brianeric26 Posted January 17, 2017 Author Share Posted January 17, 2017 look theres is the perfect and bright b/w picture dirrectly taken from the vdp Quote Link to comment Share on other sites More sharing options...
+nanochess Posted January 18, 2017 Share Posted January 18, 2017 Ok, you have a probably good VDP and the colors in expansion module #1 are looking well. So the problem would be in the R-Y and B-Y pins route. Check R40, C62, C66, R41, C63 and C67, probably a capacitor has a broken leg. Quote Link to comment Share on other sites More sharing options...
Brianeric26 Posted January 18, 2017 Author Share Posted January 18, 2017 thanks man you really help me out to repair my colecovision , so I desolder de video board from the main boad and looked around and none of the resistor or capacitors where bad but I choose to reflow the solder on them and when I solder back the video board I noticed some broken traces where the two board meet up so I fix them with a wire and yayy it works like it should do , I dont know if it was a bad solder joint on the caps or the broken traces on the board but hey it works now thank you very much man 3 Quote Link to comment Share on other sites More sharing options...
+nanochess Posted January 19, 2017 Share Posted January 19, 2017 I'm pretty glad everything went right Now another Colecovision is in the block! Quote Link to comment Share on other sites More sharing options...
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