Re: TECH: Asteroids (Long Post)

First: UNPLUG THE MONITOR!!! When your game board isn't working
correctly you can burn the screen or worse...
Second, flip the self test switch and listen for the beep/boops, this
will inform you if the RAM is good/bad and give you an idea of which one
(with the manual handy).
Third, I would take a real close look at the IC sockets, they are
probably no good, not grabbing the ROMs well...

John :-#)#

> Jeff Bovee wrote:
>
> Well I'm deep into repairing my asteroids game and I could use some
> suggestions. When I turn the game on I get red LEDs on both the pcb
> and the
> monitor board. The monitor is running (properly I believe) I think
> the
> problem lies in the pcb, both of the player select LEDs are blinking
> rapidly
> and an occasional hot spot appears on the screen but does not move and
> then
> will disappear and reappear somewhere else. At one point I did get
> the test
> patern up when I put it into self test, but I couldn't get this to
> repeat.
>
> I put my ocilliscope probe on the X and Y test points on the pcb and
> over
> the course of 5 minutes or so the signal would move from +.5 to -.25
> to -1v
> (these are gross approximations) at each level it would hold for 5 or
> 10
> seconds and then change to the new level. These changes corresponded
> with
> the hot spot changing its position, but it seemed to me it should have
> been
> clocking much faster. I put the probe on the 6Mhz clock test point
> and was
> able to see the clock, very ugly looking wave form, only a slight
> resemblance to anything square.
>
> I know this is a long post so thanks for reading the entire entry and
> any
> help you can offer I would really appreciate. I may have forgotten
> something so if you have any questions about specific details of the
> machines opperation, post them and I will respond a.s.a.p. Thanks
> again for
> any help you guys can provide.
>
> Sincerely
> Jeff Bovee
>
> Update:
>
> I checked the power at the board with my fluke meter and it read
> 5.04vdc
> which seems pretty good. I also removed and cleaned all of the
> socketed
> chips and cleaned the board edge connector. While I was doing this I
> noted
> a blob of solder on the pcb and investigated further, only to find a
> really
> botched up logic chip. It was a sn74161 and two of the legs had been
> busted
> off and it looked like somone with a blowtorch had tried to reattach
> them.
> Very poor workmanship, tsk... tsk.. tsk..
>
> Well I dug out some of my electronics components from college and
> rummaged
> through a tray of chips, and low and behold when I had almost given
> up, the
> second to the last chip in the tray was a 74161, hooray! I desoldered
> the
> old one and inserted the new. I wanted to stick in a socket instead
> of
> soldering on the chip directly but the only socket I had was missing a
> leg.
>
> After reconnecting the edge connector I powered it up, and still
> nothing.
> Still no activity on the x or y outputs and the LED's on the player
> select
> buttons have stopped blinking (don't know if that's good or bad). I
> could
> really use some suggestions from any of you people who have worked on
> an
> Asteroids pcb before. Thanks in advance for any help that can be
> rendered.
>
> Best Regards
> Jeff Bovee

-- 
 John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9     
 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)  
 mailto:jrr_at_flippers.com, web page http://www.flippers.com      
        "Old pinballers never die, they just flip out."