Asteroids cabaret - need PCB help!

[Carsten Carlos]

Hi!

Somehow I havn't found a service manual for the cabaret version of the
Asteroids-pcb.

Selftest tells me that RAM#3 is defective, but at position M4
I only find a 74LS86P, which I think is only a logic IC, am I right? Also there is no picture in service mode. In the Asteroids encyclopedia it seems like the 74LS191 at K5 might be the problem, but again, there is
none at this position on my PCB!

In game mode, P1&P2 flashed rapidly and the game continuous making fast
resets, at least I can see the gamescreen right, except a diagonal line
across the screen.

I have a very high res picture of the pcb (2,7MB) here.
http://www.retrospieler.de/images/asteroids/Asteroids%20PCBhighres.JPG

Also you can see the problem at my homepage at http://www.retrospieler.de
under BONUS / ASTEROIDS.

Anyone an idea?

[dabone]

Thats a bootleg.


Real asteroids boards look like this.





Good luck finding any repair guides for that.


Later,
dabone

[Carsten Carlos]

Thanx, well, a bootleg in an original Atari cab - at least it would've been worse the other way around. 

[RayB]

On a real Atari board, if one of those many capacitors fails (or say, is broken off) it will report a RAM error for that row that the capacitor is next to.

So find the ram reported bad, then find the related capacitor and check to make sure it's properly soldered in.

[Carsten Carlos]

Oh, thats a good one, at least at some capacitors (from the many brown types) the cover is partly broken, though they may still function. I'll 've a look at them.

Also I'm searching for a good source for these RAM chips, at least I've found one source in the US so far, but none here in germany.

[RayB]

Sure but keep in mind, if the capacitor is bad and you fix it, your RAM problem will go away.

If you replace the RAM but the real problem is the capacitor, well, you'll have wasted time and money on a RAM chip for nothing.

The capacitor ensure that the RAM receives proper voltage. If it goes bad, then the RAM doesn't get the proper voltage and then appears faulty.

[Carsten Carlos]

Sure, I just hoped I can get the RAMs on my local electronic store, too - in the US they are only $1.6 each so it might be a good idea to have some at home. The main error absolutely matches the problem with the 74LS191, which are only $.40 here, so I'll at least get some and a bunch of capacitors.

[ChadTower]

May as well swap caps anyway, they're going to fail at some point.

[Carsten Carlos]

Anyone knows if 200ns is fast enough for the RAM? Found some at a german shop for 1.75 each.

[SirPeale]

May as well swap caps anyway, they're going to fail at some point.

I *think* the caps in question are mylar caps, not electrolytic ones.

[ChadTower]

They're probably those disc shaped ceramic ones... but still more prone to failure than your average IC.

[Carsten Carlos]

I found the bad RAM and have socketed them all - now error has changed:

In selftest I get the diagonal lines and the small greyscale and one small number (guess the coin multiplier), but it resets constantly and beeps shortly.

I game mode, one asteroid at the topleft-corner hangs and the coin notice at the bottom is displayed twice, game resets repeatedly and S1+S2 blinks accordingly.

So more then one error in this board, I guess? Any ideas?