Re: Star Wars Vector RAM

Hi Alan,
Got parts and replaced LS42 at 2K Vector Address Decoder, still didn't work, proceeded on to LS244 chips at 1&2M, 1&2N, still not working, so looking at schematics on sheet 12A I decided to replace Vector Interface Buffer LS244 at 1P and Vector Memory Data Buffer LS245 at 1K, and it still gives me a boop sound on 6th tone indicating something wrong with RAM 4P. Put logic probe on the pins of all aforementioned chips and found a signal at everyone, don't know if they are correct or not, that's beyond my knowledge. Can you or anyone else think of anything else to check?
Thanks,
Rich

----- Original Message -----
  From: Alan McCormick
  To: vectorlist@vectorlist.org
  Sent: Sunday, May 22, 2011 7:11 PM
  Subject: Re: VECTOR: Star Wars Vector RAM

  If the power supply issues check OK and the vector RAMs are known good (zero oxidation on all pins/use a dremel wire brush to polish the pins), check the Vector Address Decoder @ 2K (74LS42). If replacing that doesn't fix it, then you need to check the 74LS244 chips @ 1M/2M/1N/2N. Download the schematics and print out the AVG pages so you can take notes. This shouldn't be too hard to fix - good luck.

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  From: Rich Harkoff <rharkoff1@new.rr.com>
  To: vectorlist@vectorlist.org
  Sent: Sunday, May 22, 2011 3:50 PM
  Subject: VECTOR: Star Wars Vector RAM

  Hello,
  My Star Wars quit working a few days ago, no video. To try and track down the problem I ran the self test and I heard a low tone on the 6th indicating a bad RAM at 4p, after swapping with another working RAM, ran test again same problem showed up bad RAM at 4p. I swapped 3 chips in all and each time #6 beep/boop would indicate 4p being bad. So figuring problem was elsewhere I got the trusty meter out and ran continuity from each pin of 4p to all the other 5 RAMS, all tested fine, pin 18 of 4p RAM goes to 2K pin 6 and that checked ok too, even changed the socket to make sure it wasn't flakey. Anyone have any thoughts on what is going on with the board?
  Thanks for your time,
  Rich
  Green Bay

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Received on Fri May 27 21:02:31 2011