mtarallo Posted June 8, 2018 Share Posted June 8, 2018 Hi guys - was wondering if any of have come across this issue where there isn't any video but there is audio with a Sega Genesis Model 1? I'll try to be as detailed as possible to avoid the obvious troubleshooting steps: The video via RF or Composite A/V does not seem to work I am getting a black screen when the console is powered on - on a regular tube type TV using the RCA inputs - yellow (video) white (audio) The games DO boot up Audio does work from the headphone jack Audio comes out of the TV speakers I can hear through the audio that the controls ARE working - select menus, fire, jump sounds etc. So I believe we can rule out a cart and/or CPU issue and/or memory issues The same power supply, games and A/V and RF cables WORK in my other model 1 genesis I removed and looked at the PCB, removed the heat sinks - all caps, surface mount resistors seem great - there is a little flux residue around the voltage regs - but nothing looks swollen or burnt. I looked for dry solder joints and just for certainty I re-soldered the A/V Connector and RF modulator I searched the internet and did not find anything specific to my problem - other than threads mentioned cart and pin cleanings and then eventually go unsolved I know these are not terribly expensive, - it is more principal really - it seems like it may be a simple fix - but I don't know enough about what can go wrong in an IC I think I exhausted all steps. If you have experienced this and have some suggestions - thank you. Regards Mike Quote Link to comment Share on other sites More sharing options...
Taijigamer Posted June 8, 2018 Share Posted June 8, 2018 Sounds like u have eliminated everything else. It might point towards a malfunctioning video DAC. I would eliminate caps first. A bad cap doesn't always look like a bad cap. What model Genesis 1 do u have. There should be a decoupling cap for the CXA1145, maybe try replacing that first. 1 Quote Link to comment Share on other sites More sharing options...
mtarallo Posted June 8, 2018 Author Share Posted June 8, 2018 Thank you - it is a model 1601 - I'll take a look and test some caps! Quote Link to comment Share on other sites More sharing options...
mtarallo Posted June 8, 2018 Author Share Posted June 8, 2018 so it seems that the caps are charging and discharging - not sure if it as the correct rates - but I tested each cap with 1K ohms and watched the numbers on the meter charge and then discharge - unless I am doing something wrong. Smaller caps discharged faster than others (seems reasonable) - testing those on mV and large caps on v. At one point after the system ran for a little - the video did come on and then went back off. I think I have invested all the time I am willing to at this point unless I get some new information. Thanks for your efforts. Quote Link to comment Share on other sites More sharing options...
mtarallo Posted June 8, 2018 Author Share Posted June 8, 2018 (edited) One more update - in regards to what I said about the game (video) coming on for a few seconds - seems to only occur with Gunstar Heros - when Gunstar Heroes is in - you can hear the intro screen and all that - and at one point - the screen flashes when it comes to the start menu and the TV comes on and shows the start screen and then flickers off - that is weird - seems like a refresh problem now. Why would the screen come on at that point? Watch the video of it in action: happens around 1:17 Edited June 8, 2018 by mtarallo Quote Link to comment Share on other sites More sharing options...
Taijigamer Posted June 9, 2018 Share Posted June 9, 2018 That's interesting. That suggests a sync issue in the video signal which might explain why your Tv won't detect picture, or only show it randomly. I would try and replace the cap on the video line. It's a 220uf cap near the cxa-1145 chip. The schematics show it as C32 but yours might be slightly different. The resistance test doesn't show whether a cap has gone bad. U need an ESR tester which can be expensive. I just troubleshoot down to the likely cap and replace it. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted June 9, 2018 Share Posted June 9, 2018 Bad crystal maybe? Quote Link to comment Share on other sites More sharing options...
mtarallo Posted July 10, 2018 Author Share Posted July 10, 2018 UPDATE: I did it! - it works! - more of principal really - as I could have probably got another functioning model 1 for $30 - lol -but just a few bucks in caps and a new IC and some hours here and there troubleshooting - but yes - if you are referring to the Sony CXA1145P IC - that was the final fix for the video problem, possibly did not need to replace the caps - I honestly should have started with that first - but I'm learning!!! 1 Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted July 10, 2018 Share Posted July 10, 2018 Wow...I don't think I've actually seen an 1145 go bad before. Course like anything it certainly possible as obviously was the case here. Glad you got it working! 1 Quote Link to comment Share on other sites More sharing options...
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