FW: Help! Asteroids! Please!!!!!!!

> Gang,
>
> I had trouble with my Asteroids about 2 months ago. The screen was blank
> and
> the watchdog was barking. I did all the usual stuff (even caps on both the
> PCB
> and AR board) and then started searching with a logic probe. But the test
> screen was functioning - and it said there were no errors?????
>
> I gave up and the machine sat dark until this week when I got a dlx board.
> I
> turned it on to ensure the monitor was still working and the game came
> up!!!!
> Okay!!! The X/Y size was shrunk by about a 1/3 but I adjusted that and it
> was fine.
>
> I played it for about an hour and it went down. Must be heat related. Turn
> to
> the test screen and it is fine. Turn back to the game and it is fine
> again.
> Play for about 30 minutes and black. Turn off for 30 seconds and turn back
> on
> and it's fine.
>
> This time after about 30 minutes I started to see a few random vectors
> during
> the game, then a couple of flashes where everything was super big, then
> the
> asteroids were jumping ahead instead of smooth movement.
>
> Switch to test screen and now I'm getting rom errors on the F1 rom. Good.
> Test
> a couple of times more and I get different errors but always on the F1
> chip.
> Finally, the game went off never to return. Now the self test is giving a
> contant FF error on F1 meaning all bits failing.
>
> Check the rom and it's fine.
>
> Replace the socket - no difference.
>
> Check F1 and pin 20 is being held high.
> Check the next rom and same thing.
> Checked third rom and pin 20 is pulsing.
>
> Trace the pin 20's back to the 74139 and they are being held high there.
> Not
> knowing the difference in a stuck bit and a diliberate high signal with a
> probe - I replace that chip too. No difference.
>
> Inputs to the 74139 are pulsing all the way back to the 6502.
>
> So any ideas now???
>
> The test screen is nice but I'd rather play the game.
>
> As always - all help appreciated.
>
> Cheers
> MacMan
>
> PS: Following my "God life is hard in Australia" I had several E-Mails
> from
> list members offering to hold stuff and ship it to Australia. Next week
> I'll
> investigate getting a Star Wars upright shipped.
>
> It wasn't my intention to post a WTB ANYTHING AT ALL!!! Thank you all for
> your
> generous offers. Looks like I may have already spent my Y2K bonus before I
> get
> it. Happy Y2K - Australia's first and I'll let you know if the world ends.
>
> PPS: In New York for the Millenium next year (you know - the real one for
> people who can count)
>
Received on Thu Dec 30 15:00:01 1999