Re: SEGA G80 - Star Trek Draw Problem..

Sorry for the slow response,,,, here is the latest,,,, -Ok after doing some tracing with a Logic Probe (not that easy since I have to view  the Control Card from the backside) here is what I found / where I am at: U42 - Pin 3 - MemW - Low (U42 was replaced) U42 - Pin 4 - MemW - Pulsing - U41 - Pin 5 - High - (U41 was replaced) U41 - Pin 6 - High - connects to Pin10 (All RAMS)  U24 - U31 - Pin 10 - Low (All 2114 RAMS replaced) U38 - Pin 9 - MemR - High (U38 was replaced) U38 - Pin 8 - MemR - Low U40 - Pin 1 - Mux - High (U40 was not replaced) Open to any ideas / will keep looking, in the interim. Thanks, Regards, _Arcadius  ________________________________ From: Arcadius Stempak <arcademanx@yahoo.com> To: "vectorlist@vectorlist.org" <vectorlist@vectorlist.org> Sent: Tuesday, April 10, 2012 9:30 AM Subject: Re: VECTOR: SEGA G80 - Star Trek Draw Problem.. Thanks again, will follow your suggestions and provide an update.   Regards, _Arcadius From: Douglas Gauck <douglas@gauck.com> To: vectorlist@vectorlist.org Sent: Monday, April 9, 2012 10:16 PM Subject: Re: VECTOR: SEGA G80 - Star Trek Draw Problem.. If all vectors are bad, yet they're still within the bounds of the screen, it seems the counters and such for position are working, but they're working from bad data that's in (or not in) the video RAM. Stuck may be the word... next I'd look for stuck lines on either side of the '244s (there are more at U20, U21, U35, U36) and the '245. Maybe reading or writing but not both (activity at U42, U41)? -DrG On Apr 9, 2012, at 10:57 PM, Arcadius Stempak wrote:    Well, first of all ' Thank you ' I appreciate any and all reaponse regarding this ' odd ' problem.... > Ok here is what I did (including my results)... > > >Verified Continuity between Pin 8 (2114 RAM) U27 and U31 Pin 8 and U46 Pin 4 - Continuity is ' Good '. >Replaced LS244's at U48 and U49 - no change, problem still the same. >Replaced LS374 at U13 - no change, problem still the same.  >Replaced LS245 at U14 - no change, problem still the same. >Replaced all 6 Diodes (with new ones) - no change - problem still the same. >Replaced LS139 at U46 - no change, problem still the same. >Replaced U1 to U5 - again (since I had socketed these) - with no change.  > > >Nothing looks correct anywhere on the screen - random lines being drawn / blanked / drawn all over the place. >(I call it repeated ' misdraw ' ) > > >So here is what I tried - out of curiousity - . > > >Pulled Each Ram (2114) one at a time - then initiated CPU - Self Test (Red Button) -  >(As one would figure - CPU Always comes up (initially - OK - since it has its own RAM)... however.... >The end Result of Removing Each and Every Ram (2114) chip is that no matter what or which one is removed >(including U27) the Test Always (even with All Ram chips removed) will begin to Fail and get Stuck at U27. > > >It's as if this Control Card was ' stuck ' on U27 and ignores All other Faults, including its own Ram  >(that is unless the System is designed to Read - Ram - starting at U27? - first?) > > >I also say the above, since even after pulling (for Test purposes).... > > >2114 (Ram) between U24 - U31 <--- with Memory removed there is no picture, but U27  still indicates Fault. >LS244's at U48 and U49, >LS245 at U14, >LS283 at U33,  > > > At this point I am open to try just about anything, in order to try to get this thing going. >  > Only thing I did not do yet is hook up to a Scope.... but if anyone thinks that's a good idea I will do this. > >Thanks, > > >Regards, >_Arcadius 
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Received on Thu Apr 12 22:37:37 2012