Antic Posted July 24, 2018 Share Posted July 24, 2018 Hi Im trying to fix this Commodore 64 but so far no success. When I power it up I get a line on screen (look at picture), after about 3 minutes the chips are slowly getting worm except for the PLA,SID and Kernal they get hot but just enough so that they can still be touched, i probed with my scope pins 1 and 39 on cpu and the clock seems fine ,how do I proceed from here I am suspecting the PLA but dont have another Commodore to test it I heard that I could test the chips using a arduino but probably would need a code for that. Quote Link to comment Share on other sites More sharing options...
shoestring Posted July 28, 2018 Share Posted July 28, 2018 Suspect a dead PLA unless proven otherwise. A dead SID should not prevent a c64 from booting, unless its shorted directly to gnd which may may prevent it from doing so. You'll see a blank screen or sometimes jumbled multicoloured screen. Pull the SID chip out and see if it boots, a c64 should always boot without one if that's the only fault on the board. What are your +5v voltages like ? Since you have a scope. What does RST ( pin 40 ) do on power up ? ( should toggle from low for half a second and hold high ). Any activity on the Address and Data pins ?. If they toggle for a short time after cold reset then get stuck ( low or high ).. suspect bad DRAM or mask rom. Any DRAM chips get hot to the touch? Check pin 38( R/W ), * What is it doing?. This determines what the next DRAM access will be ( Either a read or a write ). A low indicates a write, a high should indicate a read. * Pin 39 should always be high when a r/w access occurs. * Are any data pins from the 6510 floating during a write access ? ( r/w low ). Quote Link to comment Share on other sites More sharing options...
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