Monitor Issue / Asteroids Ship Glitch

if i wanted to shotgun the issue would purchasing 3 of these and replacing at each location be a good chance at solving the problem? or are there other ic's i should by as well? or is this a terrible approach and buy the probe and learn how to use it?
thanks
blake


I don't recommend shotgunning IC on these boards, as it's easier than you think to cause a new problem while replacing a chip (pull a trace, cause a short, etc.) You can end up introducing new problems without knowing it, which will cause you to run in circles.

Logic probes are $18, and while they don't solve everything, they can give you new information that may help you solve your problem. Definitely worth the investment if you're going to own an arcade game.

http://www.ebay.com/itm/281871438998
 
I don't recommend shotgunning IC on these boards, as it's easier than you think to cause a new problem while replacing a chip (pull a trace, cause a short, etc.) You can end up introducing new problems without knowing it, which will cause you to run in circles.

Logic probes are $18, and while they don't solve everything, they can give you new information that may help you solve your problem. Definitely worth the investment if you're going to own an arcade game.

http://www.ebay.com/itm/281871438998

very good. thanks again for the help andrew.
blake
 
If you haven't figured it out already, be very careful with traces on Asteroids (and many other Atari boards of the same era). It is VERY EASY to lift traces on these.

As mentioned, using flush cutters to cut the legs, then use needle nose pliers and a soldering iron to heat up and remove the cut leg, then apply some fresh solder and desolder the hole clear. That will give you the best chance of not lifting a trace. I've repaired a couple of Asteroids boards with lifted traces. It is tedious work to fix them from lifted traces, so best not to have any lift in the first place.

A logic probe is a great tool for looking for lines stuck high or low.... especially if you have a good board to compare against as well.

In lieu of that, if you have a DVM with a diode setting, you can with the board powered off and removed, check for shorts to GND or +5V on any suspect chip. Most chips will read a lower voltage drop in one direction, and a higher one in the other direction (like a diode), but what you are looking for are legs that are wide open or shorted. I don't use this technique anymore, but the first PCB I fixed (Space Invaders), I did this and found 2 bad chips, replaced them and it fixed the board. I probed the entire board, so it was tedious, and not an educated means of finding a fault, but it worked.

If you do find a short to ground or +5V on a chip, be aware sometimes legs are grounded or pulled high.... you do need to check the schematic before you make a decision that this might be an actual fault. Also, as chip outputs are tied to chip inputs, if you find a short on an input of one chip, it is more likely it is a short on the output of a chip feeding it. Though inputs can short as well. Worst case you end up replacing 2 chips when only one was bad.

Good luck finding your problem.
 
If you haven't figured it out already, be very careful with traces on Asteroids (and many other Atari boards of the same era). It is VERY EASY to lift traces on these.

As mentioned, using flush cutters to cut the legs, then use needle nose pliers and a soldering iron to heat up and remove the cut leg, then apply some fresh solder and desolder the hole clear. That will give you the best chance of not lifting a trace. I've repaired a couple of Asteroids boards with lifted traces. It is tedious work to fix them from lifted traces, so best not to have any lift in the first place.

A logic probe is a great tool for looking for lines stuck high or low.... especially if you have a good board to compare against as well.

In lieu of that, if you have a DVM with a diode setting, you can with the board powered off and removed, check for shorts to GND or +5V on any suspect chip. Most chips will read a lower voltage drop in one direction, and a higher one in the other direction (like a diode), but what you are looking for are legs that are wide open or shorted. I don't use this technique anymore, but the first PCB I fixed (Space Invaders), I did this and found 2 bad chips, replaced them and it fixed the board. I probed the entire board, so it was tedious, and not an educated means of finding a fault, but it worked.

If you do find a short to ground or +5V on a chip, be aware sometimes legs are grounded or pulled high.... you do need to check the schematic before you make a decision that this might be an actual fault. Also, as chip outputs are tied to chip inputs, if you find a short on an input of one chip, it is more likely it is a short on the output of a chip feeding it. Though inputs can short as well. Worst case you end up replacing 2 chips when only one was bad.

Good luck finding your problem.

thanks for all the info. your description of removing an ic is exactly how i replaced two so far that had error codes. i do have a dmm and will try troubleshooting with it and give any results. i plan on buying a logic prob and learning how to use it as im finding the physical repair of the boards not to difficult with the skills ive gained from my work.
thanks
blake
 
The physical skills are one piece and it sounds like you're coming up to speed there.

The skills of deciphering where to look for problems when looking at the schematics and a set of symptoms are a bit more. I've got a pretty solid understanding of the various components and circuits you would put together from them.... but sometimes you can look at a circuit and scratch your head thinking 'WTF are they doing here ?'. For example, looking at parts of the xy timing and xy control circuits for Sega G-80 (Star Trek and others) vector games.... there are a few where you end up figuring out stuff, and figure out what some of the signal lines do.... but can easily get left with nagging questions about the stages/steps/states the circuit goes through.

Best of luck with the repair. You might get lucky and find a shorted or open leg using your DMM (btw, that 'trick' is good for TTL logic chips, I am unsure how to apply that to CMOS (4000 series) or other types of chips such as the AtoD converters, op-amps, etc (you could still find shorts, but I'm not sure what sort of readings beyond short would be 'normal')).
 
so i removed the speed mod and put in the 161 ic off the daughter board that was socketed no prob. but after reinstalling and powering up i got a blank screen unless i put in test mode which i got the same screen as before with the dashes. the thing that really sucks is after on for a few minutes i started smell burning. i was in the back of the cab and it was coming from the monitor area not down by the board. what i would like to do is properly bulletproof the monitor. i have worked and discharged many raster monitors but never a vector and if i remember correctly the discharge process is different and even the tool used is specific? let me know if there is a write up or doc that encompasses all of this, and ill be happy to take any advice here as well.
thanks
blake
 
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