Re: Asteroids Deluxe Problem

Thanks for the tip Matt. I recently acquired a scope and I suppose it's time for me to dig in
and learn how to use it properly.

There is an error in my original post which states that pin 21 is pulsing on the defective
board and high on the good board. I am a beginner at this and read the pins backwards! Pin 40
on the defective board is pulsing which means it is in a constant state of RESET.

I grounded the WatchDog and put the game in test mode. This produced one long never ending
beep. Probably meaningless but I decided to interpret it as ram failure at L1. I piggybacked
a new 2114 and the beep went away. I replaced it on the board and received the never ending
beep again. Tried to piggyback several other new 2114's but the same beep persisted. I
plugged in the monitor and noticed the spot killer was off but only scrolling diagonal lines
are displayed. I suppose that's progress of a sort.....:-)

Matt Rossiter wrote:

> Do you get anything when you put the game into self test mode? If you look at that
> troubleshooting document I would try some of the steps under "Paul's Tips" - particularly
> B2. Personally, I've never had much luck with logic probes except when it comes to
> measuring clock signals. I like to use an oscilloscope so that I can see what's going
> on. If you're able to borrow a signature analyzer from someone - I like to use Peter
> Fyfe's signature analysis help guide on gamearchive.com.
>
> That's my bit of advice.
>
> Matt
>
> George Campbell wrote:
>
> > I'm having trouble diagnosing a problem on an Asteroids Deluxe board.
> > When the game is powered up, the Player 1 and 2 buttons flash too
> > quickly and the monitor's spot killer is on. The game does not play
> > blind. I have established the following:
> >
> > 1) Logic supply is a steady 5.25v. DAC supply from VR3 is 4.98(is this
> > too low?)
> > 2) All roms were checksummed and are good.
> > 3) Tried working Ast Dlx board in the cab and it works fine.
> > 4) Swapped out the 6502 from the dead board in the working board and it
> > is good.
> > 5) Replaced Y1 as it had broken off. Could not find a 12.096 mhz crystal
> > locally so I substituted a 12.000mhz.
> > 6) Removed and socketed L5. Isolated pin 1 and checked pin 40 of the
> > 6502 - was stuck low. I found this test here:
> > http://www.geocities.com/SiliconValley/Circuit/2940/asteroidtech/asteroidsrepair.html
> >
> > According to the above page, if pin 40 is low, the problem could lie
> > within the MPU, the vector state machine or both. However, I found this
> > test inconclusive as pin 40 on the good board was also stuck low and it
> > works fine.
> > 7) Checked E2 with a logic probe and compared results to the working
> > board. Both were identical.
> > 8) Probed the 6502 on both boards. The only difference was that pin 21
> > on the good board was high and 21 on the problem board was pulsing.
> >
> > Note: Dip switch settings on the good board are identical to those on
> > the dead board.
> >
> > Any suggestions on how to proceed?
> >
> > Thanks
> > George
> >
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Received on Sun Jul 8 14:33:35 2001